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Over 3000 years ago the Chinese and Hebrews were advocating cleanliness in food, water and personal hygiene.
STUDENT LEARNINGIn this unit students will:• distinguish between infectious and non-infectious disease• explain why cleanliness in food, water and personal hygiene practices assists in
the control of disease• identify the conditions under which an organism is described as a pathogen.
STUDENT ACTIVITIESStudents will:• identify data sources, plan and choose equipment or resources to perform a fi rst-hand
investigation to identify microbes in food or in water• gather, process and analyse information from secondary sources to describe ways in
which drinking water can be treated, and use available evidence to explain how these methods reduce the risk of infection from pathogens.
THE IMPORTANCE OF CLEANLINESS
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s• explain why cleanliness in food, water and personal hygiene practices assists in
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s• explain why cleanliness in food, water and personal hygiene practices assists in
• identify the conditions under which an organism is described as a pathogen.
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s• identify the conditions under which an organism is described as a pathogen.
• identify data sources, plan and choose equipment or resources to perform a fi rst-hand
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• identify data sources, plan and choose equipment or resources to perform a fi rst-hand investigation to identify microbes in food or in water
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investigation to identify microbes in food or in water
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• gather, process and analyse information from secondary sources to describe ways in
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• gather, process and analyse information from secondary sources to describe ways in which drinking water can be treated, and use available evidence to explain how these
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which drinking water can be treated, and use available evidence to explain how these
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methods reduce the risk of infection from pathogens.Sample
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methods reduce the risk of infection from pathogens.
Heinemann Biology HSC212
lnfectious and non-infectious diseaseDisease, or impaired functioning of an organism, may come from within the organism itself. It may also be the result of damage caused by another organism or by adverse non-living factors in the environment. Disease can be infectious or non-infectious.
Infectious disease is caused by an infecting organism, which could be microscopic or macroscopic. A pathogen is an infective agent that causes disease. Some examples of pathogens that aff ect humans are given in Tables 3.1 and 3.2.
Non-infectious diseases may develop as a result of genetic inheritance, nutritional defi ciencies or environmental factors. Some examples are given in Table 3.3.
TABLE 3.1 Some diseases caused by microscopic pathogens in humans
Prions Viruses Bacteria Protozoans FungiCreutzfeld-Jacob
disease (CJD)infl uenza tonsilitis amoebic
dysentryringworm
fatal familial insomnia (FFI)
herpes tuberculosis giardia dandruff
kuru poliomyelitis gonorrhea malaria tinea
Alpers syndrome AIDS tetanus sleeping sickness
thrush
TABLE 3.2 Some macroscopic organisms that can cause disease in humans
External parasites(ectoparasites)
Internal parasites(endoparasites)
head louse tapeworm
body louse fl ukes
crab louse threadworm, pinworm
bed bug hookworm
fl ea fi larial worm
tick roundworm
itch mite whipworm, giardia parasite, malarial parasite
TABLE 3.3 Categories and examples of non-infectious disease in humans
Category Examplesinherited haemophilia, Down syndrome, cystic fi brosis, phenylketonuria,
Huntington’s disease
nutritional scurvy, beri-beri, anorexia nervosa, kwashiorkor, tooth decay
environmental skin cancer, lung cancer, heavy metal poisoning, asbestosis, hearing loss, stress, asthma
lnflnDistinguish between infectious and non-infectious disease.
• Microscopic means too small to be seen with the unaided eye.
• Macroscopic means visible with the unaided eye.
The terms ‘infectious’, ‘contagious’ and ‘communicable’ all mean diseases that can be passed from one organism
to another.
Non-infectious diseases may develop as a result of genetic inheritance, nutritional
defi ciencies or environmental factors.
BIOFACTGiardia is caused by the parasite Giardia lamblia. It is contracted by drinking contaminated water or by close contact with an infected person. The parasite interferes with the body’s ability to absorb fats and vitamins, causing diarrhoea, nausea and other symptoms. The disease is treated by the administration of drugs such as quinacrine and metronidazole.
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sSome diseases caused by microscopic pathogens in humans
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sSome diseases caused by microscopic pathogens in humans
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sPrions Viruses Bacteria Protozoans Fungi
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sPrions Viruses Bacteria Protozoans FungiPrions Viruses Bacteria Protozoans Fungi
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sPrions Viruses Bacteria Protozoans Fungiinfl uenza tonsilitis amoebic
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sinfl uenza tonsilitis amoebic infl uenza tonsilitis amoebic
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sinfl uenza tonsilitis amoebic dysentry
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sdysentry
herpes tuberculosis giardia dandruff
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sherpes tuberculosis giardia dandruffherpes tuberculosis giardia dandruff
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sherpes tuberculosis giardia dandruffherpes tuberculosis giardia dandruff
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sherpes tuberculosis giardia dandruff
kuru poliomyelitis gonorrhea malaria tinea
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skuru poliomyelitis gonorrhea malaria tineakuru poliomyelitis gonorrhea malaria tinea
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skuru poliomyelitis gonorrhea malaria tineakuru poliomyelitis gonorrhea malaria tinea
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skuru poliomyelitis gonorrhea malaria tinea
Alpers syndrome AIDS tetanus sleeping
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sAlpers syndrome AIDS tetanus sleeping Alpers syndrome AIDS tetanus sleeping
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sAlpers syndrome AIDS tetanus sleeping
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TABLE 3.2
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TABLE 3.2 Some macroscopic organisms that can cause disease in humans
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Some macroscopic organisms that can cause disease in humans
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External parasites
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External parasites(ectoparasites)
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(ectoparasites)head louse
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head louse
Non-infectious diseases may develop as
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Non-infectious diseases may develop as a result of genetic inheritance, nutritional
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a result of genetic inheritance, nutritional defi ciencies or environmental factors. Sam
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defi ciencies or environmental factors.
The search for better health 213
Contributing factorsTh ree interacting factors contribute to health and disease:1 the host organism2 the agent of disease3 the environment.
Th e hostOrganisms vary in their resistance to infection; individuals vary, and the resistance of a particular individual can vary with time.
Interpersonal variationsA healthy person might resist an infection that is devastating to someone whose defences are poor for some reason. For example, elderly people are often more prone to illness than younger people; and AIDS suff erers have very little resistance, so the infections they catch often have unusually severe eff ects.
Personal variationsPeople under stress may succumb to an infection (e.g. a common cold) that they might resist at another time.
Resistance and immunityWhether or not people suff er from disease as a result of infection by a particular pathogen depends partly on their ability to fi ght the infection. Humans have defences with which to fi ght diseases; this protection and immunity is discussed in detail in Unit 3.5.
BehaviourBy adopting a healthy lifestyle we can reduce our susceptibility to many diseases (e.g. through a healthy diet and exercise), and by participating in screening programs we may reduce the severity of a disease (e.g. by early detection of melanoma).
Th e agent of disease
Specifi cityMost infective agents infect only one species—humans do not usually share infections with other organisms. For example, cat infl uenza is not passed to humans, nor is human infl uenza passed to pets. A pathogen can usually grow only in a particular host, and only within certain tissues of the host.
Infective doseIt is possible that contact with a pathogen does not result in disease because the dose is too small. An infective dose is one that is in suffi cient quantity to cause disease. Th e virulence of a pathogen is its ability to cause disease.
Eff ect on hostMost pathogens stimulate defensive reactions in the host, including increased white blood cell production, and they are often accompanied by fever and tiredness. Depending on the pathogen, the infection will be localised in one part of the body (e.g. cold sores), widespread (e.g. infl uenza), intense (e.g. poliomyelitis), or trivial (e.g. head lice).
Three interacting factors contribute to health and disease:
1 the host organism
2 the agent of disease
3 the environment.
Figure 3.5Keeping fi t and taking
part in healthy activities reduces our susceptibility to many diseases.
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sPeople under stress may succumb to an infection (e.g. a common cold) that they
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sPeople under stress may succumb to an infection (e.g. a common cold) that they
er from disease as a result of infection by a particular
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s er from disease as a result of infection by a particular
ght the infection. Humans have
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s ght the infection. Humans have
ght diseases; this protection and immunity is discussed
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s ght diseases; this protection and immunity is discussed
By adopting a healthy lifestyle we can reduce our susceptibility to many diseases (e.g.
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By adopting a healthy lifestyle we can reduce our susceptibility to many diseases (e.g. through a healthy diet and exercise), and by participating in screening programs
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through a healthy diet and exercise), and by participating in screening programs we may reduce the severity of a disease (e.g. by early detection of melanoma).
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we may reduce the severity of a disease (e.g. by early detection of melanoma).
Most infective agents infect only one species—humans do not usually share Sample
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Most infective agents infect only one species—humans do not usually share infections with other organisms. For example, cat inflSam
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infections with other organisms. For example, cat inflSample
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Heinemann Biology HSC214
Th e environmentTh e nature of the environment will aff ect the likelihood of a pathogen growing and being passed from one host to another. Standards of housing, water supply, sewerage and air pollution are all important in this regard. Many infectious agents are spread in crowded, unhygienic conditions.
Figure 3.6With no running water or hygienic sewage and rubbish disposal, people
living in slums risk contracting serious diseases such as cholera and typhoid fever.
Cleanliness and control of diseaseControl measures can stop the spread of infectious diseases, particularly if we know how a disease is transmitted (see pp. 233–235). General hygiene and cleanliness are important in reducing the transmission of infectious diseases. Cleanliness may be at the personal level, such as hand washing, and, for a society, may include government legislation and controls regulating public health issues such as sewage disposal, water purity and the handling of food for sale.
Many ancient civilisations recognised the importance of cleanliness in food, water and personal hygiene. Th e third book of the Old Testament of the Christian Bible (Leviticus, Chapters 11 and 13) sets down hygienic practices that included personal cleanliness, protection of water and food supplies, and protection from the spread of infectious diseases, particularly the identifi cation and treatment of leprosy. Th e Minoans and Cretans had drainage systems and fl ushing toilets, and the ancient Romans had public baths, sewers and carefully maintained water supplies.
Th e Chinese were writing about health and medicine as long ago as 2500 bc. Th ey believed that good health was the correct balance of two energy forces in the body, Yin and Yang. Disease resulted from an imbalance, which could be treated by acupuncture and herbal treatments.
Muslims have always maintained a high level of personal hygiene. Cleanliness and purifi cation are part of the requirements of Islamic faith.
CleC
BIOFACTLegionnaire’s disease, which can cause death, is spread by breathing in airborne droplets containing Legionella bacteria. These bacteria normally occur in soil, but can thrive in other warm, moist environments. The water towers of air-conditioning plants in buildings provide suitable conditions for their growth and have been the source of many outbreaks of the disease.
Explain why cleanliness in food, water and personal hygiene practices assists in the control of disease.
Cleanliness is important because it is in this way that the spread of infectious disease can be prevented or minimised.
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With no running water or hygienic sewage and rubbish disposal, people
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With no running water or hygienic sewage and rubbish disposal, people living in slums risk contracting serious diseases such as cholera and typhoid fever.
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living in slums risk contracting serious diseases such as cholera and typhoid fever.
Cleanliness and control of disease
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Cleanliness and control of diseaseControl measures can stop the spread of infectious diseases, particularly if we know
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Control measures can stop the spread of infectious diseases, particularly if we know how a disease is transmitted (see pp. 233–235). General hygiene and cleanliness
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how a disease is transmitted (see pp. 233–235). General hygiene and cleanliness are important in reducing the transmission of infectious diseases. Cleanliness may
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are important in reducing the transmission of infectious diseases. Cleanliness may be at the personal level, such as hand washing, and, for a society, may include Sam
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be at the personal level, such as hand washing, and, for a society, may include government legislation and controls regulating public health issues such as sewage Sam
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government legislation and controls regulating public health issues such as sewage disposal, water purity and the handling of food for sale.Sam
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disposal, water purity and the handling of food for sale.Sample
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hygiene practices assists in the
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hygiene practices assists in the
The search for better health 215
Food practicesContamination of food may be visible, such as dirt or insects, or it may be invisible to the naked eye, such as contamination by microorganisms. Diseases caused by contaminated food include salmonella poisoning, clostridial food poisoning and botulism. Hygienic food handling reduces the spread of diseases such as food poisoning. Th ere are many general hygiene rules relating to food, such as:• Use clean utensils and plates. • Do not sneeze or cough over food.• Wash hands after using the toilet. • Store perishable food in refrigerator.• Cover cuts or sores before handling food.• Do not use food that has fallen to the fl oor.
In Australia there are national standards relating to food that include food safety standards. All states have legislation to regulate the handling of food for sale and the sale of food. In New South Wales, the Food Act 2003 and the Food (General) Regulation 2004 regulate these matters. Th eir requirements are detailed, and inspection of any premises selling food must be allowed.
Water suppliesTh e provision of clean water and the disposal of waste water and sewage is a public health issue. Water supplied to houses must be pure and safe to drink. Water is usually fi ltered and chlorinated by a licensed operator before it can be supplied to people. Similarly, waste water and sewage collected from people’s properties can only be released by an operator with a licence to discharge effl uent. Diseases that may be contracted from polluted water include typhoid, cholera and giardia.
Personal hygieneAustralians have high standards of personal hygiene. Th ink of some of the ways in which you keep yourself and your home clean. Personal hygiene is about washing ourselves, hands, hair and body, regularly. Hands should always be washed after using the toilet, before making or eating food, after handling dogs or other animals, and after contact with someone sick or something dirty. Personal hygiene also includes brushing and fl ossing teeth, wearing clean clothes, being careful not to sneeze or cough on others, putting used personal items such as tissues in a bin, and keeping our homes clean, especially kitchen and bathroom areas. Doing these things helps us avoid infectious diseases, and prevents their spread.
Clause 15 of the Australian Food Safety Standard 3.2.2 includes the following:
A food handler must take all reasonable measures not to handle food or surfaces
likely to come into contact with food in a way that is likely to compromise the
safety and suitability of food.A food handler must wash his or her
hands whenever his or her hands are likely to be a source of contamination of
food, immediately before working with ready-to-eat food, after handling raw food and immediately after using the
toilet.
In 2009, the World Health Organization published guidelines for all health-
care workers on handwashing, called ‘SAVE LIVES: Clean Your Hands’. It is
part of a major global effort supporting health-care workers to improve hand hygiene and thus stop the spread of
life-threatening, health-care-associated infection.
Figure 3.7Good personal hygiene
means washing hands before handling and eating food. Using tongs when serving food and wearing protective gloves and clothing minimises the chances of transmitting diseases.
Recycling water—Homebush Bay Olympic siteThis reuse system reclaims and recycles sewage and stormwater. It involves:• a water reclamation plant to harvest water from sewage• a stormwater storage reservoir• a water treatment plant to fi lter and disinfect water• a supply system to pipe water to the Olympic site and nearby areas
The recycled water is clear and odourless but is not for drinking. It is used for toilet fl ushing and irrigation. This has three major benefi ts:• drinking water is not wasted• the volume of sewage entering the sewer system is reduced• stormwater is utilised.
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s e provision of clean water and the disposal of waste water and sewage is a public
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s e provision of clean water and the disposal of waste water and sewage is a public
health issue. Water supplied to houses must be pure and safe to drink. Water is
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shealth issue. Water supplied to houses must be pure and safe to drink. Water is
ltered and chlorinated by a licensed operator before it can be supplied to
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s ltered and chlorinated by a licensed operator before it can be supplied to
people. Similarly, waste water and sewage collected from people’s properties can
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speople. Similarly, waste water and sewage collected from people’s properties can only be released by an operator with a licence to discharge effl
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sonly be released by an operator with a licence to discharge effl uent. Diseases that
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s uent. Diseases that only be released by an operator with a licence to discharge effl uent. Diseases that only be released by an operator with a licence to discharge effl
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sonly be released by an operator with a licence to discharge effl uent. Diseases that only be released by an operator with a licence to discharge efflmay be contracted from polluted water include typhoid, cholera and giardia.
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smay be contracted from polluted water include typhoid, cholera and giardia.
Australians have high standards of personal hygiene. Th ink of some of the ways in
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Australians have high standards of personal hygiene. Th ink of some of the ways in which you keep yourself and your home clean. Personal hygiene is about washing
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which you keep yourself and your home clean. Personal hygiene is about washing ourselves, hands, hair and body, regularly. Hands should always be washed after
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ourselves, hands, hair and body, regularly. Hands should always be washed after using the toilet, before making or eating food, after handling dogs or other
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using the toilet, before making or eating food, after handling dogs or other animals, and after contact with someone sick or something dirty. Personal hygiene
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animals, and after contact with someone sick or something dirty. Personal hygiene ossing teeth, wearing clean clothes, being careful not
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ossing teeth, wearing clean clothes, being careful not also includes brushing and fl ossing teeth, wearing clean clothes, being careful not also includes brushing and fl
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also includes brushing and fl ossing teeth, wearing clean clothes, being careful not also includes brushing and fl
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to sneeze or cough on others, putting used personal items such as tissues in a bin, Sample
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to sneeze or cough on others, putting used personal items such as tissues in a bin, and keeping our homes clean, especially kitchen and bathroom areas. Doing these Sam
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and keeping our homes clean, especially kitchen and bathroom areas. Doing these things helps us avoid infectious diseases, and prevents their spread.Sam
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things helps us avoid infectious diseases, and prevents their spread.
In 2009, the World Health Organization
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sIn 2009, the World Health Organization published guidelines for all health-
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s published guidelines for all health-care workers on handwashing, called
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scare workers on handwashing, called
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INVESTIGATION
216 Heinemann Biology HSC
Students will: identify data sources, plan and choose equipment or resources to perform a fi rst-hand investigation to identify microbes in food or in water.
ldentifying microbes
IntroductionMicrobiology is the study of microbes or microorganisms. Microbes are present everywhere—in air, water and food. Some of these microbes cause human disease, some are benefi cial to humans and some have no effect on us at all. Individual microbes are too small to be seen unless they are magnifi ed. However, many organisms cluster together to form colonies as they reproduce, and our unaided eye can see these colonies—for example, as mould growing on bread.
Bacteria and fungi often reproduce by means of microscopic spores, which will develop into colonies when conditions are favourable. Many microbes will reproduce in a laboratory if they are provided with suitable conditions such as warmth (incubated at 25–35°C), moisture and nutrients (dishes of nutrient agar medium). After incubation, plates can be examined macroscopically for growth. It is best to examine the microbes through the lid if possible, because some of the growth may contain pathogenic organisms.
Colonies are usually distinguished by their size, shape, surface profi le and colour. Bacterial colonies can be distinguished from fungal colonies by observation. Bacterial colonies are generally quite small, shiny and coloured. Fungal colonies are fl uffy and quite large. Table 3.4 and Figure 3.12 illustrate the features used to characterise microbes.
When working with microbes you need to ensure that you do not become infected with anything and that the experimental material does not become contaminated with organisms other than those you are studying. The use of sterile techniques is always essential in microbiological work.
Purpose1 To practise using some sterile microbiologial techniques.
2 To practise some culturing techniques.
3 To examine macroscopically a range of microbes found in water.
4 To examine macroscopically a range of microbes found in food.Note: Not all of the above activities need to be carried out at once. Because of time constraints you may wish to focus on one specifi c task.
A Sterile techniques
ProcedureRead the information on the following pages.
Skills and outcomesH11, H12, H13, H14
Type of activityFirst-hand investigation
MaterialsIncubator, sterile nutrient agar plates: for water; for air; for food (yoghurt agar requires addition of powdered milk). Bunsen burner, sterile pipettes, inoculating loop, inoculating needle/probe, sticky tape, marking pens, disposable gloves, water samples from a variety of sources, yoghurt, mould from fruit, vegetables or bread, methylated spirits
See:• Processing information
from secondary sources• Presentation and
interpretation of data
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sMicrobiology is the study of microbes or microorganisms. Microbes are present
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sMicrobiology is the study of microbes or microorganisms. Microbes are present everywhere—in air, water and food. Some of these microbes cause human disease, some
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severywhere—in air, water and food. Some of these microbes cause human disease, some are benefi cial to humans and some have no effect on us at all. Individual microbes are too
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sare benefi cial to humans and some have no effect on us at all. Individual microbes are too small to be seen unless they are magnifi ed. However, many organisms cluster together
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ssmall to be seen unless they are magnifi ed. However, many organisms cluster together to form colonies as they reproduce, and our unaided eye can see these colonies—for
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sto form colonies as they reproduce, and our unaided eye can see these colonies—for example, as mould growing on bread.
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sexample, as mould growing on bread.
Bacteria and fungi often reproduce by means of microscopic spores, which will
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sBacteria and fungi often reproduce by means of microscopic spores, which will
develop into colonies when conditions are favourable. Many microbes will reproduce in
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sdevelop into colonies when conditions are favourable. Many microbes will reproduce in a laboratory if they are provided with suitable conditions such as warmth (incubated at
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sa laboratory if they are provided with suitable conditions such as warmth (incubated at 25–35°C), moisture and nutrients (dishes of nutrient agar medium). After incubation,
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s25–35°C), moisture and nutrients (dishes of nutrient agar medium). After incubation, plates can be examined macroscopically for growth. It is best to examine the microbes
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splates can be examined macroscopically for growth. It is best to examine the microbes through the lid if possible, because some of the growth may contain pathogenic organisms.
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through the lid if possible, because some of the growth may contain pathogenic organisms.Colonies are usually distinguished by their size, shape, surface profi le and colour.
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Colonies are usually distinguished by their size, shape, surface profi le and colour. Bacterial colonies can be distinguished from fungal colonies by observation. Bacterial
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Bacterial colonies can be distinguished from fungal colonies by observation. Bacterial
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colonies are generally quite small, shiny and coloured. Fungal colonies are fl uffy and quite
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colonies are generally quite small, shiny and coloured. Fungal colonies are fl uffy and quite large. Table 3.4 and Figure 3.12 illustrate the features used to characterise microbes.
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large. Table 3.4 and Figure 3.12 illustrate the features used to characterise microbes.When working with microbes you need to ensure that you do not become infected
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When working with microbes you need to ensure that you do not become infected with anything and that the experimental material does not become contaminated with
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with anything and that the experimental material does not become contaminated with organisms other than those you are studying. The use of sterile techniques is always Sam
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organisms other than those you are studying. The use of sterile techniques is always essential in microbiological work.Sam
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essential in microbiological work.
PurposeSample
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Purpose
mould from fruit, vegetables or
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mould from fruit, vegetables or
Inv
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3.2
con
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217The search for better health
Opening a Petri dish• When opening a Petri dish, place the dish on a table and lift the lid at an angle of no
more than 45° (Figure 3.8).• Do not breathe over the dish, and work as quickly as possible.• After closing the dish, seal it by securing the lid with sticky tape.
Sterilising with heat-fl amingBefore using any equipment such as an inoculating loop, test tube or probe, pass it through the blue fl ame of a Bunsen burner (Figure 3.9).Using an inoculating loopInoculating loops help to spread the microbes out thinly, in order to isolate colonies.• Hold the loop like a pencil.• Using the edge of the loop and making sure not to dig into the agar, move the loop
gently over the surface of the agar in a sweeping motion (see Figure 3.10).• Only ever use a small amount of inoculum on the loop.Techniques for inoculating platesTwo methods of inoculating plates are shown in Figure 3.11.Characterising coloniesFor parts B, C and D use Figure 3.12 and Table 3.4 to characterise each colony type, particularly the features that distinguish the microbes.
45°
lightly moveinoculating loopover agar surface
inoculum containingmicroorganisms
Figure 3.8Opening the lid of a Petri dish
Figure 3.10Using an inoculating loop
Figure 3.9Sterilising your equipment.
(a) Move test tube lip in fl ame before adding or extracting material. (b) Draw inoculating loop through fl ame as shown. Wait until the loop glows red before removing it from the fl ame.
CAUTIONAlthough the microbes used in the activities in this manual are considered ‘safe’, standard microbiological procedure requires that you regard all microbes as being potentially harmful. You do not have complete control over what actually grows.
movementof testtube
blueflame
hold plug oftest tube inopposite hand
heat centreof wire tored hot
direction ofmovement
move slowly to heat remaining wire and loop to red hot
a
b
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sFor parts B, C and D use Figure 3.12 and Table 3.4 to characterise each colony type,
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sFor parts B, C and D use Figure 3.12 and Table 3.4 to characterise each colony type,
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Incubator use• Bring the temperature to the required level before starting the experiment.• Check the temperature control regularly.• Plates should be stacked and placed upside down in the incubator unless you are
culturing water samples. In this way condensation does not form on the agar surface and the label can be read.
Treatment and disposal of material• Place all used equipment in containers of disinfectant provided.• Reusable items will be disinfected or autoclaved (sterilised in a pressure cooker)
before being washed and reused.• Plastic equipment, including used agar plates, will be disinfected and autoclaved
before disposal.Personal protection• If possible wear protective clothing such as a lab coat, safety glasses and disposable
gloves.• Wash and dry hands thoroughly after the removal of safety equipment, before leaving
the laboratory.• Never open an agar plate after the experiment has been set up.
B Culturing techniques
Procedure
1 Sterilise the workbench area by swabbing with alcohol.
2 Collect four sterile Petri dishes that contain nutrient agar.
3 Leave one plate unexposed, seal with sticky tape and label as the control.
4 Select three locations around the school where you predict that the type and variety of microorganisms might be different.
5 Expose plates in the chosen areas for 15 minutes, seal with sticky tape and label the bottom of the Petri dish with the location, group name/initials, date and incubation temperature.
6 Incubate the plates for three days at 25°C.
rotate Petri dishstart
finish
inoculum
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Figure 3.11Inoculation of plates
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s• Check the temperature control regularly.• Plates should be stacked and placed upside down in the incubator unless you are
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culturing water samples. In this way condensation does not form on the agar surface
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sculturing water samples. In this way condensation does not form on the agar surface and the label can be read.
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sand the label can be read.
Treatment and disposal of material
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before being washed and reused.
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before being washed and reused.• Plastic equipment, including used agar plates, will be disinfected and autoclaved
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• Plastic equipment, including used agar plates, will be disinfected and autoclaved before disposal.
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before disposal.Personal protection
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Personal protection• If possible wear protective clothing such as a lab coat, safety glasses and disposable
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• If possible wear protective clothing such as a lab coat, safety glasses and disposable gloves.
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gloves.• Wash and dry hands thoroughly after the removal of safety equipment, before leaving
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• Wash and dry hands thoroughly after the removal of safety equipment, before leaving the laboratory.Sam
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the laboratory.• Never open an agar plate after the experiment has been set up.Sam
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• Never open an agar plate after the experiment has been set up.
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TABLE 3.4 Colony characteristics
Colony characteristic DescriptionApproximate size In millimetres
Colonial form Punctiform, rhizoid, etc.
Margin Entire, lobate, etc.
Elevation Convex, subsurface, etc.
Surface Smooth, rough, shiny, matt, moist, dry
Colour Presence of pigment
Opacity Translucent, opaque
(from Odlum C, Garner R & Sakker E (1988) Human Disease. Sofi ma, Sydney)
Results
1 Copy Table 3.5 into your workbook and record the results. Identify, count and record the number of colonies and types of microbes in air. (If the colonies form a matt cover over entire plate, record the number as >200.)
TABLE 3.5 Numbers and types of bacteria and fungi present in air samples
Where tested Bacteria Fungi
Number of colonies
Number of types
Number of colonies
Number of types
Control
1
2
3
punctiform
circular
filamentous
filamentous
irregular
rhizoid
granular
erose
lobateundulate
entire
curled
flat raised convex pulvinate umbonatesubsurface
a Colonial forms of growth
Elevation characteristics
Margin of bacterial coloniesb
c
Figure 3.12Terms used to describe
macroscopic characteristics of growth
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Punctiform, rhizoid, etc.
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Entire, lobate, etc.
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Entire, lobate, etc.
Convex, subsurface, etc.
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Convex, subsurface, etc.
Smooth, rough, shiny, matt, moist, dry
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Smooth, rough, shiny, matt, moist, dry
Presence of pigment
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Presence of pigment
Translucent, opaque
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Translucent, opaque
Human Disease
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Human Disease. Sofi ma, Sydney)
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. Sofi ma, Sydney)
Copy Table 3.5 into your workbook and record the results. Identify, count and Sample
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Copy Table 3.5 into your workbook and record the results. Identify, count and record the number of colonies and types of microbes in air. (If the colonies form a
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record the number of colonies and types of microbes in air. (If the colonies form a Sam
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220 Heinemann Biology HSC
2 Using Table 3.4 and Figure 3.12, characterise up to fi ve colony types, noting particular macroscope features such as size, colour, surface, etc.
Discussion
1 How does the alcohol sterilise the workbench?
2 Predictions can often be called hypotheses. How are they useful in scientifi c investigations?
3 Why are labels placed to the outside of the Petri dish as in Figure 3.13?
C Microbes in water
Procedure
1 Sterilise the workbench area with alcohol.
2 Collect four sterile Petri dishes that contain nutrient agar.
3 Leave one plate unexposed, seal with sticky tape and label.
4 For each water sample place 0.5 mL onto the agar plate using a sterile pipette. Close the lid and gently rock the water sample so that it spreads evenly over the entire plate.
5 Seal with sticky tape and label correctly.
6 Incubate all plates for three days at 30°C.
Results
Record your results in a table similar to Table 3.5. Identify, count and record the number of colonies and types of microbes in water. Describe each colony macroscopically.
D Microbes in food
Procedure
1 Sterilise the workbench area with alcohol.
2 Collect four sterile Petri dishes:a 2 nutrient agarb 2 nutrient agar with powdered milk.
3 Collect a sample of mouldy food and a sample of yoghurt.
4 a For the fi rst two dishes, leave one plate as the control, seal and label correctly. Using an inoculating probe, collect a small sample of mould and place it in the centre of the second plate. Seal and label correctly.
b For the second two dishes, leave one plate as the control, seal and label correctly. Streak the second plate with yoghurt using an inoculating loop (see Figure 3.10). Seal and label correctly.
5 Incubate the fi rst two plates at 25°C for 2–5 days. Incubate the second two plates upside down at 35°C for two days.
6 Construct a table in your workbook to identify, count and record the colonies present in your Petri dishes and describe their macroscopic features.
Lab
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32°C
Figure 3.13Correct labelling of the
underside of a Petri dish
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sCollect four sterile Petri dishes that contain nutrient agar.
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Leave one plate unexposed, seal with sticky tape and label.
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sLeave one plate unexposed, seal with sticky tape and label.
For each water sample place 0.5 mL onto the agar plate using a sterile pipette.
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sFor each water sample place 0.5 mL onto the agar plate using a sterile pipette. Close the lid and gently rock the water sample so that it spreads evenly over the
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Seal with sticky tape and label correctly.
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Incubate all plates for three days at 30°C.
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Record your results in a table similar to Table 3.5. Identify, count and record
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the number of colonies and types of microbes in water. Describe each colony macroscopically.
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macroscopically.
D Microbes in food
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D Microbes in food
Procedure
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1 Sterilise the workbench area with alcohol.
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The search for better health 221
Results
1 Your yoghurt plate should contain two different colonies of bacteria. What techniques could you use to isolate each culture into a pure culture?
2 In what ways do your fungal colonies differ from the bacterial colonies you observed?
3 Compare results for procedures B, C and D.
Discussion (for parts B, C and D)1 Why was it necessary to have controls for each of the experiments?
2 What differences were there in the types of microbes in water and in food?
3 What differences were there in the number of microbes in water and in food?
4 How did the microbes get into the mouldy food you tested? How did they get into the yoghurt?
5 Why is it essential to use sterile techniques when working with microbes?
PathogensOrganisms are called pathogens when they cause disease. To cause disease, organisms need the right conditions to multiply and be transmitted. Cleanliness and hygienic practices discourage the growth and spread of microorganisms. Practices such as heating food to a high enough temperature, pasteurising, preserving, freezing and irradiation can ensure that microorganisms are destroyed. Chemicals such as chlorine, detergents and disinfectants either kill or discourage growth and therefore reduce the number of potentially pathogenic organisms.
Some microorganisms fl ourish in warm weather but die in the cold. For example, tinea, a fungal infection of the skin, fl ares up in summer when conditions are hot and humid; colder, drier weather is not suitable for its growth and reproduction, and few people suff er from the disease in winter.
Certain diseases are known as tropical diseases because they originate and fl ourish in tropical climates where temperatures are high all year round and the rainfall is also high. Examples include malaria, giardia and kala-azar (leishmaniasis). In cold conditions the organisms do not survive.
Crowded, dirty, unsanitary conditions encourage the spread of disease. After natural disasters such as earthquakes and fl oods there is always a concern about the spread of disease, because fresh water supplies, cooking facilities and sewage disposal might not be available to the survivors.
How diseases are spreadAirborne Dust and droplets in the air may carry microorganisms. Colds and infl uenza are spread by inhaling contaminated droplets in the air from people coughing and sneezing. Contaminated dust from clothes and bedding can spread disease.Contact Diseases spread by contact, either direct or indirect, are called contagious diseases. Athlete’s foot is a fungal disease that can be picked up in showers and changing rooms. Contact with bodily fl uids such as saliva or blood
PaPIdentify the conditions under which an organism is described as a pathogen.
BIOFACTAntiseptics and disinfectants are chemicals that kill most bacteria and fungi and some viruses, but they do not usually destroy spores. They act unselectively on any microorganisms they contact. Antiseptics and disinfectants reduce the number of pathogens present. Sterilisation by boiling in water for 10–20 minutes removes nearly all living things present, including bacterial spores. Chlorine kills bacteria in water. The maximum level of chlorine in drinking water should be 5 mg per litre, according to the National Health and Medical Research Council.
Organisms are called pathogens when they cause disease.
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sOrganisms are called pathogens when they cause disease. To cause disease, organisms need the right conditions to multiply and be transmitted. Cleanliness
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sorganisms need the right conditions to multiply and be transmitted. Cleanliness and hygienic practices discourage the growth and spread of microorganisms.
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sand hygienic practices discourage the growth and spread of microorganisms. Practices such as heating food to a high enough temperature, pasteurising,
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sPractices such as heating food to a high enough temperature, pasteurising, preserving, freezing and irradiation can ensure that microorganisms are destroyed.
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preserving, freezing and irradiation can ensure that microorganisms are destroyed. Chemicals such as chlorine, detergents and disinfectants either kill or discourage
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Chemicals such as chlorine, detergents and disinfectants either kill or discourage growth and therefore reduce the number of potentially pathogenic organisms.
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growth and therefore reduce the number of potentially pathogenic organisms.Some microorganisms fl ourish in warm weather but die in the cold. For example,
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Some microorganisms fl ourish in warm weather but die in the cold. For example, tinea, a fungal infection of the skin, fl ares up in summer when conditions are hot
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tinea, a fungal infection of the skin, fl ares up in summer when conditions are hot and humid; colder, drier weather is not suitable for its growth and reproduction,
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and humid; colder, drier weather is not suitable for its growth and reproduction, er from the disease in winter.
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er from the disease in winter.Certain diseases are known as tropical diseases because they originate and
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Certain diseases are known as tropical diseases because they originate and ourish in tropical climates where temperatures are high all year round and the Sam
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ourish in tropical climates where temperatures are high all year round and the rainfall is also high. Examples include malaria, giardia and kala-azar (leishmaniasis). Sam
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rainfall is also high. Examples include malaria, giardia and kala-azar (leishmaniasis). Sample
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In cold conditions the organisms do not survive.Sample
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In cold conditions the organisms do not survive.Crowded, dirty, unsanitary conditions encourage the spread of disease. After
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Crowded, dirty, unsanitary conditions encourage the spread of disease. After
INVESTIGATION
222 Heinemann Biology HSC
from an infected person can also transmit disease. Bleeding cuts and scratches should always be covered.Faeces Contact with faecal matter from an infected person or animal, or from contamination of food or the water supply, may spread disease. Typhoid and cholera may be spread in this way. Proper disposal of sewage is important, as are personal hygiene practices such as washing hands after going to the toilet and before handling food.
By other organisms Other organisms, known as vectors, may transmit diseases. For example, malaria is transmitted by mosquitoes of the genus Anopheles (see pp. 239–240).
Figure 3.14A serious tinea infection
Diseases spread by contact are called contagious diseases. Contact may be
direct (for example, glandular fever by kissing) or indirect (for example,
infl uenza by inhaling airborne droplets from a cough or a sneeze).
BIOFACTEbola is an RNA virus that was first identified in Zaire, Africa, in 1976. The disease is spread by close personal contact (or contaminated needles). Ebola is a virulent disease—the death rate is about 90%. There is no cure.
IntroductionThe provision of clean water and the disposal of waste water is a public health issue, and water supplied to houses must be pure and safe to drink. Water is usually treated chemically before it is supplied. However, in many developing countries, treatment of water is minimal. Water is a carrier for many contaminants that can be the cause of disease. Dysentery, caused by swallowing contaminated water, can cause fever, nausea, cramps and convulsions.
To ensure that water is of good quality and that drinking guidelines are met, water quality testing and monitoring takes place at every stage of the supply system. Samples are taken in the catchment area, after the water has been treated and in the distribution pipelines. Water is tested for more than 70 different characteristics including taste, colour, odour, microorganisms and chemical content.
Skills and outcomesH12, H13, H14
Type of activitySecond-hand data activity
MaterialsBooks, journals, internet sites. Investigation 3.3 worksheet, available from Pearson Places
Treatment of drinking waterStudents will: gather, process and analyse information from secondary sources to describe ways in which drinking water can be treated, and use available evidence to explain how these methods reduce the risk of infection from pathogens.
See Processing information from secondary sources
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For example, malaria is transmitted by mosquitoes of the genus
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Treatment of drinking water
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Treatment of drinking waterStudents will:
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Students will: gather, process and analyse information from secondary sources to
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gather, process and analyse information from secondary sources to describe ways in which drinking water can be treated, and use available evidence to
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describe ways in which drinking water can be treated, and use available evidence to
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explain how these methods reduce the risk of infection from pathogens.
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explain how these methods reduce the risk of infection from pathogens.
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Purpose• To gather, process and analyse information on drinking water treatment and
quality.
• To explain how water treatment methods reduce the risk of infection from pathogens.
Background information: understanding your waterMicrobial indicatorsColiform bacteria have been traditionally used since the nineteenth century as microbial indicators of the cleanliness of the water and the possible presence of disease-causing microorganisms. Coliforms is the group name given to many different types of rod-shaped bacteria. Coliforms include not only faecal coliforms, such as Escherichia coli found in the gut of humans and warm-blooded mammals, but also other types of harmless bacteria found in vegetation and soil. Today, modern testing methods make it possible to test directly for E. coli and enterococci bacteria, as more sensitive indicators of faecal contamination and therefore health risks to drinking water.Cryptosporidium and GiardiaThese disease-causing microorganisms occur in the gut of infected warm-blooded animals. They can be introduced into the water supply through dead animal carcasses and faeces.TurbidityTurbidity is a measure of suspended material in water, which may cause it to look muddy or discoloured.ColourWater should be virtually colourless.ChlorineTo ensure good-quality drinking water, chlorine is added to kill bacteria that may cause disease. Tests are carried out for the residual level of chlorine, which needs to be present after treatment to make sure that the water is disinfected all the way to the tap.FluorideSmall amounts of fl uoride are added for dental health reasons, in accordance with legislation.Aluminium, iron and manganeseThese substances occur naturally in water at low levels and may be responsible for taste and staining problems with water.Australian Drinking Water GuidelinesAustralian Drinking Water Guidelines are specifi c standards that provide the Australian community and the water supply industry with guidance on what constitutes good-quality drinking water. The guidelines err on the side of safety, setting contamination values lower than the level considered safe. They include both health-related guidelines and aesthetic guidelines. Health-related guidelines ensure that there is no signifi cant health risk to a person drinking the water, and the aesthetic guidelines cover the look, smell and taste of the water. For example, the health-related value for the presence of copper in water is not more than 2 mg/L, whereas the aesthetic-related value is 1 mg/L. The aesthetic value is lower because the higher level, while not harmful to health, affects the taste of the water.
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These disease-causing microorganisms occur in the gut of infected warm-blooded animals.
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sThese disease-causing microorganisms occur in the gut of infected warm-blooded animals. They can be introduced into the water supply through dead animal carcasses and faeces.
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sThey can be introduced into the water supply through dead animal carcasses and faeces.
Turbidity is a measure of suspended material in water, which may cause it to look muddy
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To ensure good-quality drinking water, chlorine is added to kill bacteria that may cause
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To ensure good-quality drinking water, chlorine is added to kill bacteria that may cause disease. Tests are carried out for the residual level of chlorine, which needs to be present
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disease. Tests are carried out for the residual level of chlorine, which needs to be present
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after treatment to make sure that the water is disinfected all the way to the tap.
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after treatment to make sure that the water is disinfected all the way to the tap.
Small amounts of fl uoride are added for dental health reasons, in accordance with
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224 Heinemann Biology HSC
A Research activity
ProcedureGather relevant, current information about the water supply of a named area. In your research you should include:
Name Give the name of the area where the water is drunk.Location Describe the location of the water catchment area.Management Identify who is responsible for the management of the water
supply.Treatment Describe the ways in which the water is treated.Water quality Explain which of the treatment methods reduce the risk of
infection and how the treatment improves water quality.Analysis of the water supplied for drinking Where possible, access charts of
water analysis and compare with those given in part B.
Results
Present the fi ndings from your research as a report using the headings given above.
B Water data analysis
ProcedureStudy the statistical data provided in the worksheet, from two of the water fi ltration plants, Illawarra and Warragamba, that form part of Sydney’s water supply and answer the Discussion questions that follow.
Discussion
1 Compare the total coliforms in both raw and fi ltered water in the Illawarra and Warragamba fi ltration plants. Suggest an explanation for any differences.
2 Why is the number of samples tested for Giardia and Cryptosporidium in the Warragamba fi ltration plant greater than other samples (for pH, turbidity, etc.) tested at the plant on the same water?
3 Would the water in the Warragamba fi ltration plant have been cleared for release to customers? Explain your answer.
4 The Australian Drinking Water Guidelines (ADWG) indicate safe levels of material that can be present in the water supplied to customers. What is the recommended maximum level for:
a microbiological material
b pH
c chlorine levels
d iron levels?
5 Why are there no readings for chlorine, fl uoride and trihalomethanes in raw water?
6 What do min, avg and max mean? Why are these recorded?
7 Compare the two catchment areas—Warragamba and Illawarra—with regard to the quality of their raw water.
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Present the fi ndings from your research as a report using the headings given above.
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B Water data analysis
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Study the statistical data provided in the worksheet, from two of the water fi ltration
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the Discussion questions that follow.
Discussion
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Compare
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ltration plants. Suggest an explanation for any differences.Warragamba fi ltration plants. Suggest an explanation for any differences.Warragamba fi
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C Sydney’s water supply
ProcedureRead the information below, visit the Sydney Water website, and answer the Discussion questions that follow.
Sydney’s water supply: problems and solutionsIn Sydney, Sydney Water is the authority with the responsibility of overseeing the fl ow and quality of water to homes and businesses. In 2007/08, Sydney Water supplied over 481 billion litres of water to homes and business in Sydney, the Illawarra and the Blue Mountains. Sydney Water buys its water from the Sydney Catchment Authority (SCA). It then treats the water and distributes it via a network of 21 000 km of water mains, 261 reservoirs and 156 pumping stations. Both the raw water Sydney Water buys from the SCA and the water it treats are tested for a range of chemicals and microorganisms, including pesticides, metals and pathogens. The water quality monitoring plan is agreed with NSW Health. The water is tested and monitored at every stage of the supply system. The SCA tests water in the catchments. Sydney Water tests the water immediately after it is treated, in distribution pipes and at customer taps.
Throughout 2007/08, over 7900 samples were taken from customer taps and tested against a wide range of water quality parameters in the Australian Drinking Water Guidelines.
All drinking water is treated and fi ltered to reduce sediments. Chlorination is the principal method of disinfection used by most authorities, including Sydney Water. Chlorination is very effective in killing most protozoans and other disease-causing organisms. The water is fi ltered, then disinfected with small amounts of chlorine. At each treatment plant and other specifi ed points of the water supply, careful monitoring maintains chlorine levels at a minimum.
Another disinfection method used is chloramination, which is a modifi ed form of chlorination in which a small amount of ammonia is added to the water just before the chlorine. This results in the formation of chloramines, which provide a longer-lasting means of disinfection. Fluoride is then added for dental health purposes, as required by law.
In 1998 water quality became an important issue for people living in Sydney because of the problems experienced between late July and mid-September when people became ill from drinking water found to be contaminated by two protozoans: Cryptosporidium and Giardia. These parasites are usually transmitted through water contaminated with faeces, or by direct contact with a carrier or contaminated food. The symptoms they cause are abdominal cramps, diarrhoea, nausea and vomiting.
Sydney Water blamed the contamination of its water on either the existence of a dead animal in a water catchment or a defect in the water fi ltration system. This incident resulted in upgrades and increased monitoring of water fi ltration plants.
In 2007, there was a rise in taste and odour complaints from customers in the Orchard Hills and Warragamba systems. This was thought to be due to compounds related to a large blue-green algae bloom on Lake Burragorang.
Figure 3.15(a) The Cryptosporidium
parasite. (b) At the peak of the bloom, the dominant type of algae was Microcystis, which can produce algal toxins. However, genetic investigations confi rmed that the algae was unlikely to produce toxins, and no toxins were detected in the raw water supplied for treatment.
b
a
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smicroorganisms, including pesticides, metals and pathogens. The water
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smicroorganisms, including pesticides, metals and pathogens. The water quality monitoring plan is agreed with NSW Health. The water is tested and
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squality monitoring plan is agreed with NSW Health. The water is tested and monitored at every stage of the supply system. The SCA tests water in the
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smonitored at every stage of the supply system. The SCA tests water in the catchments. Sydney Water tests the water immediately after it is treated, in
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scatchments. Sydney Water tests the water immediately after it is treated, in
Throughout 2007/08, over 7900 samples were taken from customer
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sThroughout 2007/08, over 7900 samples were taken from customer
taps and tested against a wide range of water quality parameters in the
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staps and tested against a wide range of water quality parameters in the
All drinking water is treated and fi ltered to reduce sediments. Chlorination
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sAll drinking water is treated and fi ltered to reduce sediments. Chlorination
is the principal method of disinfection used by most authorities, including
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is the principal method of disinfection used by most authorities, including Sydney Water. Chlorination is very effective in killing most protozoans and
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Sydney Water. Chlorination is very effective in killing most protozoans and other disease-causing organisms. The water is fi ltered, then disinfected
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other disease-causing organisms. The water is fi ltered, then disinfected with small amounts of chlorine. At each treatment plant and other specifi ed
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with small amounts of chlorine. At each treatment plant and other specifi ed points of the water supply, careful monitoring maintains chlorine levels at
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points of the water supply, careful monitoring maintains chlorine levels at
Another disinfection method used is chloramination, which is a modifi ed
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Another disinfection method used is chloramination, which is a modifi ed form of chlorination in which a small amount of ammonia is added to the
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form of chlorination in which a small amount of ammonia is added to the water just before the chlorine. This results in the formation of chloramines, Sam
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water just before the chlorine. This results in the formation of chloramines, which provide a longer-lasting means of disinfection. Fluoride is then added Sam
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which provide a longer-lasting means of disinfection. Fluoride is then added for dental health purposes, as required by law.Sam
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for dental health purposes, as required by law.
In 1998 water quality became an important issue for people living in Sam
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In 1998 water quality became an important issue for people living in Sam
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226 Heinemann Biology HSC
UNIT REVIEW
In response, Sydney Water upgraded its water fi ltration plants at Orchard Hills and Warragamba to help reduce further water quality complaints. This included installing powder activated carbon dosing facilities to remove taste- and odour-causing compounds. These two treatment plants are the only ones entirely reliant on Warragamba Dam.
The bloom at the dam wall dissipated in December 2007, with residual algal cells remaining in the surface water. Algae continued to be present in the upper end of Lake Burragorang throughout the summer of 2007/08, but had declined by August 2008 with the start of cooler weather.
(some excerpts taken from Sydney Water Annual Report, 2008)
Discussion
1 Using your understanding of part B and the information above, why have the Australian Drinking Water Guidelines been developed, and what do they outline?
2 Explain why Cryptosporidium and Giardia are seen as potential health risks.
3 Describe three methods employed by Australian water authorities to treat drinking water.
4 Explain how these methods reduce the risk of infection from pathogens.
Summary• An infectious disease is caused by infecting organisms such as bacteria and viruses.
A non-infectious disease is caused by other factors, such as genetic inheritance, the environment or nutritional defi ciencies.
• An organism is described as a pathogen when it causes disease.
• Cleanliness in food, water and personal hygiene help to control disease by reducing the risk of infection and by controlling its spread.
The importance of cleanlinessOver 3000 years ago the Chinese and Hebrews were advocating cleanliness in food, water and personal hygiene.Sam
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s are seen as potential health risks.
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Australian water authorities to treat drinking
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sAustralian water authorities to treat drinking
how these methods reduce the risk of infection from pathogens.
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s how these methods reduce the risk of infection from pathogens.
The importance
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The importance
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of cleanliness
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of cleanlinessOver 3000 years ago the Chinese and Hebrews were advocating Sam
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Over 3000 years ago the Chinese and Hebrews were advocating cleanliness in food, water and personal hygiene.Sam
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cleanliness in food, water and personal hygiene.
227The search for better health
Unit
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3.
2
Questions1 Identify how washing hands before handling food is likely to help control disease.
A Hand washing reduces the spread of contaminants.
B Hand washing with soap is the most effective way to kill pathogens on the skin.
C Hand washing is mandated by the Food Act 2003.
D Hand washing breaks the chain of infection from one person to the next.
2 Select the most accurate statement about pathogens.
A Any microorganism has the potential to be pathogenic if it fi nds a suitable environment in which to multiply.
B Pathogens are organisms that cause disease when they multiply.
C Most pathogens fl ourish in warm, tropical conditions and regress in cooler climates.
D Pathogenicity is specifi c to the host, but is modulated by the environment.
3 ‘Typhoid Mary’ was the fi rst person in whom it was recognised that a healthy ‘carrier’ is able to spread typhoid fever. Mary was a cook in New York from 1900 to 1907 and in that time she infected 53 people, three of whom died.
Select the most likely explanation for the spread of this disease.
A Mary was infected by a person she cooked for and then transmitted the disease via airborne droplets.
B Typhoid fever is a highly contagious bacterial infection.
C At that time there was no knowledge of antiseptics and disinfectants.
D The disease is spread in food or water, contaminated with the person’s urine or faeces.
4 Distinguish between infectious and non-infectious diseases.
5 List three types of non-infectious disease, and name an example of each.
6 List some practices that help to ensure foods are not spoilt by pathogenic organisms.
7 Identify three personal hygiene practices and, for each, explain how this practice helps prevent disease.
8 When culturing microorganisms in the laboratory, we use strict sterile techniques. List these techniques and explain why they are important.
9 Outline the ways in which disease-causing microorganisms are spread.
10 Water that is collected for domestic drinking supplies is treated before being distributed. Summarise the methods and the evidence you have researched about water treatment, to explain why it is so effective in reducing the risk of infection from potential pathogens.
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s ‘Typhoid Mary’ was the fi rst person in whom it was recognised that a healthy ‘carrier’ is able
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s ‘Typhoid Mary’ was the fi rst person in whom it was recognised that a healthy ‘carrier’ is able Mary was a cook in New York from 1900 to 1907 and in that time she
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s Mary was a cook in New York from 1900 to 1907 and in that time she
Mary was infected by a person she cooked for and then transmitted the disease via
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s Mary was infected by a person she cooked for and then transmitted the disease via
At that time there was no knowledge of antiseptics and disinfectants.
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s At that time there was no knowledge of antiseptics and disinfectants.
The disease is spread in food or water, contaminated with the person’s urine or faeces.
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s The disease is spread in food or water, contaminated with the person’s urine or faeces.
between infectious and non-infectious diseases.
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between infectious and non-infectious diseases.
List three types of non-infectious disease, and name an example of each.
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List three types of non-infectious disease, and name an example of each.
List some practices that help to ensure foods are not spoilt by pathogenic organisms.
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List some practices that help to ensure foods are not spoilt by pathogenic organisms.
three personal hygiene practices and, for each,
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three personal hygiene practices and, for each, explain
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explain
When culturing microorganisms in the laboratory, we use strict sterile techniques. List these
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When culturing microorganisms in the laboratory, we use strict sterile techniques. List these why they are important.
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why they are important.
the ways in which disease-causing microorganisms are spread.Sample
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the ways in which disease-causing microorganisms are spread.
Water that is collected for domestic drinking supplies is treated before being distributed. Sample
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Water that is collected for domestic drinking supplies is treated before being distributed. Sample
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the methods and the evidence you have researched about water treatment, to Sample
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the methods and the evidence you have researched about water treatment, to
