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Micro-organisms (microbes)
Very small organisms usually only visible under a
microscope
Learning objectives• Label a generalised bacterial cell• Describe methods of feeding (nutrition), respiration,
excretion, and reproduction in bacteria.• Label a generalised virus• Describe the method of replication of viruses in living cells• Label a generalised fungus• Describe methods of feeding (nutrition), respiration, excretion, and
reproduction in fungi.
• Describe factors that affect the life processes (MRS GREN) of microbes.
• Describe how microbes are cultured (grown) in a laboratory.• Describe chemical control of microbes, (antiseptic, antibiotics,
disinfectant).• Explain ways in which humans use fungi, bacteria, and viruses (including;
nutrient cycles, food production, sewage treatment, composting).• Identify ways in which humans are affected (both helpful and harmful) by
bacteria, fungi, and viruses. Including; disease, food poisoning, and antibiotics.
• Explain how microbes can become resistant to antibiotics.
Fungi
Fungi
• A group of immobile organisms that feed on dead or living organisms and exposed food
• 70,000 known kinds• 50 fungi among NZ’s most threatened
species• Can be unicellular and
multi-cellular• Most common cause of
plant disease
Structure
• Hyphae: Fine feeding threads
• Sporagium: Spore capsule that produces spores
• Spores: reproductive cell, germinates and spreads out hyphae
Mass of Hyphae
MRS GREN
Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition
Movement
• Immobile
• But can spread by producing networks of hyphae.
Respiration
• Carry out aerobic and anaerobic respiration to create energy from food
Sensitivity
• Show active responses to their surroundings
Growth• Grow by spread of hyphae
Reproduction
• Asexual and sexual production of spores
• Spores germinate when they land on tissue and put out hyphae.
Excretion
• Allow waste to diffuse out of cells and into the surrounding environment
Nutrition• Secrete enzymes that break down
food, the absorb digested food• Extra-cellular digestion
Bacteriahttp://www.youtube.com/watch?v=tqOVYpkZ0qs
Bacteria
• Bacteria are unicellular organisms with no nucleus
• Sphere, rod, or spiral shaped• Usually 0.01mm in length and only visible under
the higher powers of the microscope• Over 3000 known kinds• They are found almost everywhere including in
living things • Colonies growing on agar look like shiny spots of
various colours
Spherical (coccus)
Rod shaped (bacillus)
Spiral (spirillum)
Bacteria structure
Structure functions
Cell wall: Maintains cell shapeCell membrane: Controls entry and exit of materialsChromosome: Carries genetic informationCytoplasm: fills cell and provides medium for chemical reactions to occurFlagellum: Assists the bacterium to moveCapsule: Provides protection from external environment
MRS GREN
Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition
Movement
• Many bacteria move by
hair-like threads called flagella.
• These are made up of Wqlong stands of protein
• Non-flagellum bacteria float in water or on the wind.
• Or are carried/spread by
their hosts
Respiration
• Not breathing!
• The process of releasing energy from food molecules
• Bacteria carry out:
- Aerobic respiration (requires oxygen)
- Anaerobic respiration (without the presence of oxygen)
Sensitivity
Bacteria display sensitivity to their environment.
They can move along concentration gradients until they reach their optimum environment.
i.e. Temperature/ acidity/ Oxygen/ Magnetic
Growth
In optimum conditions bacteria do grow, but their goal is reproduction so they grow up to a certain point where they have enough resources to reproduce.
Reproduction
• Reproduce asexually by a process called Binary fission
• The bacterium’s chromosome is duplicated and the cell then pinches in half and two identical
daughter cells are
produced
Excretion
Bacteria excrete by allowing waste to diffuse out of the cell membrane into the environment
i.e. CO2 from aerobic respiration
Nutrition
• Bacteria ‘feed’ by secreting enzymes which break down their food source into smaller molecules that can be absorbed by the bacteria.
• This is called
extra-cellular
digestion.
• Parasites – Live on or in larger organisms and feed off them. If they cause disease they are called pathogens.
• Saprophytes – Consume dead matter. These bacteria are scavengers and decomposers.
• Autotrophs – Self-feeders. They can make food from non-living materials i.e. chemicals/ sunlight.
- Green and purple sulfur bacteria.
Factors that inhibit bacteria growth
• Light
• Temperature
• Chemicals
• Acidity
• Food supply
Classification
• Bacteria fall into a category of life called the Prokaryotes or DNA, is not enclosed in a nucleus.
• Bacteria are the only prokaryotes. All other life forms are Eukaryotes creatures whose cells have nuclei.
Fungi and Bacteria
• http://www.icbm.de/pmbio/mikrobiologischer-garten/eng/index.php3
Microscopic hyphae Sporangia
Helpful and harmful:
Microbes and Biotechnology
Helpful Fungi
• Fungi are used in many processes including the brewing of beer and ginger beer, the making of bread and also the making of wine.
• Fungi are also used in the production of medicines such as the antibiotic penicillin.
• Mushrooms and Truffles are fungi that we eat.
Fungi - yeast
• Saccharomyces cerevisiae baker's yeast.
• Converts sugar into Carbon dioxide by anaerobic respiration causing the bread to rise
Antibiotics
• Fungi produce compounds to kill bacteria that might compete for their food source.
• We call this substance antibiotics.
• Penicillin is an example of this.
Helpful Bacteria
• Many bacteria are helpful in….– Compost, nitrogen fixing bacteria in plants
– Cellulose digesting bacteria in the gut of herbivores.
– We use yoghurt bacteria to convert the sugar in milk to lactic acid which makes yoghurt.
Escherichia coli• One of many kinds of microbes that live in
your gut.
• Helps you digest your food every day.
Lactobacillus acidophilus
• Lactobacillus acidophilus is the bacteria that turns milk into yogurt.
Bacteria and Medicine:
Bacteria can be genetically engineered to produce medical drugs.
e.g. insulin
Making Yogurt!!
• Heat 200mls of milk in a beaker until it reaches ~ 40oC (close to body temperature)
• Take of heat and add 1 tablespoon of yogurt and stir to mix.
• Seal in air tight container, and incubate.
• In a test tube, test the pH of 2mL of milk. Add some sulfuric acid until the caesin precipitates. Re-test pH
Questions
• Why did we incubate our cultures at 28oC?
• Why were the plates incubated upside down?
• What must be present in the natural yoghurt for this to work?
• Why was the milk heated first?
• Why does powder yoghurt last longer than yoghurt pots?
Bacteria and nutrient cycles
Nitrogen cycle
• Plants and animals need nitrogen to make protein but they can’t use the nitrogen in the air because they cannot break open the N2 molecules.
• Nitrogen fixing bacteria in the roots of plants like clover, convert nitrogen gas from the air into nitrates which can be used by plants as a source of nitrogen
Saprophyte
+
Nitrogen cycle
• Animals get there nitrogen by eating plants or animal protein.
• Dead animal and plant protein, and animal urine is broken down by decomposers. The nitrogen changes back to nitrates.
• Some bacteria in the soil can change nitrates back into nitrogen gas, these are denitrifying bacteria.
Nitrogen Cycle
Ginger BeerGinger beer is a non-alcoholic soft drink made by adding ginger, sugar,
water, and the fungus yeast together in a sterile container. The container is then kept in a warm place for a few days. At the end of this time, the container is heated at high temperature before the ginger beer is bottled.
(a) Name the conditions required to obtain maximum growth of the yeast fungus.(b) Explain why the container of ginger beer is heated to a high temperature before its contents are bottled.
The yeast undergoes anaerobic respiration in the container.
(c) What does anaerobic mean?(d) Name TWO products of this reaction.
Decomposers
Nitrogen fixing bacteria
Denitrifying bacteria
Helpful and harmful:
Naturally helpful:• Many bacteria and fungi are decomposers
breaking down dead tissue (e.g. in compost heaps).
• These micro-organisms release nutrients that plants can absorb. They form important parts of the nitrogen and carbon cycle.
Carbon cycle
• Carbon is released from dead matter by decomposers into the atmosphere as carbon dioxide gas, which is absorbed by plants as they manufacture food.
Brainpop
• Carbon cycle
Chemical control of microbes
Disinfectants
• Disinfectants are antimicrobial agents that are applied to non-living objects to destroy microorganisms,
• Kill microbes but may harm living tissue
• Bactericide
Examples of disinfectant
• Alcohols• Janola• Harpic• Dettol
Antiseptics• Antiseptics are antimicrobial substances
that are applied to living tissue/skin to prevent infection.
• Inhibit growth of microbes and do not harm living tissue.
• Used for sensitive areas such as mouth, open wounds, and are often diluted disinfectants
• Bacteriostatic or bacteriocide
Examples of antiseptics
• Iodine• Soaps• Listerine mouth
wash
Antibiotics
• An antibiotic is a chemical compound that inhibits the growth of bacteria in the body
• Target specific – only affects bacterial cells so has little or no side effects.
• Can be produced by fungi e.g. penicillin
Aerobic and anaerobic
Bacteria and food particle Enzymes secreted outside
Enzymes digest food particleFood enters the bacteria
A single bacterium just beforereproduction
The DNA replicates and divides
Cell membrane pinches togetherTwo bacteria are formed
0.5
1.0
Num
ber
of b
acte
ria (
mill
ions
)
100 200 300 400
Time since infection (minutes)
Growth of bacteria with time.
In ideal conditions they can reproduce every 20 minutes.This rapid increase in numbers is called exponential
growth.
Limits to growth
• They will not increase forever as eventually a lack of food or space or the build up of toxins in the form of waste products will cause the numbers to level off and then decrease.
Num
ber
of b
acte
ria
(mill
ions
)
Time since infection (minutes)
Slow growth in number
Rapid growth in number
Maximum number of bacteria
Decreasing numbers
Controlling microbes
Tangrams
• In groups complete a tangram by matching definitions to terms.
• Once finished answer below:– Describe three differences between fungi and
bacteria– How do we know bacteria and fungi are
living?– What is a saphrophyte?
Home learning
• Pages so far:
• Pages for tonight:
• DUE MONDAY!!!!!!!!!!!!
• Anaerobic =– Produces:
• Aerobic =– Produces:
Respiration is the break down of food to produce energy needed for living.
Viruses
• Viruses are simple but effective pathogens
• Viruses can infect all living things• Range from 20 to 20millionth of a
millimetre.• Can only be seen with an electron
microscope.
Viral structure
• Viruses can in a variety of shapes
• Consists of a core of genetic material surrounded by a protein coat=capsid
• Some viruses also have a membrane. This membrane can have proteins embedded in it
Viral reproduction
• Essentially all a virus is a set of instructions for making new viruses.
• MRS GREN is not followed by viruses and the only ‘living’ characteristic that they have is reproduction
• They lie on the border between the living and no living worlds
Viral reproduction• Cannot reproduce independently.
• When a virus lands on the surface of a cell it inserts its genes into the host cell.
• The viral genes take over the cells processes to produce new viruses.
• These build up in the cell until it eventually bursts releasing the new viruses into the host where they can infect new cells.
• Viruses are pathogens as the host cell is always damaged by the virus.
• Human viral diseases include:
Colds
Flu
Aids
Viruses and pest control
Some viruses can be intentionally released to control pest
e.g. calcivirus and rabbits
Harmful Microbes
Harmful to whom, that is the question?
Harmful Microbes
• A few types of micro-organisms cause disease.
• They are called pathogens.
• An infectious disease is one that can be passed on from person to person and this can happen in a variety of different ways.
Catching a disease
Contact with body fluids(e.g. blood, semen, saliva
Contact with infected materials likeTowels and handkerchiefs
Through the airContaminated food or water
Skin contact
Some of the ways to get sick
Just because you are exposed to these daily does not mean you will get sick!!
Pathogenic micro-organisms
• When a pathogen grows in your body an infection occurs.
• The pathogen may damage tissue or produce toxins that poison cells.
• http://www.brainpop.com/health/bodysystems/immunesystem/
1. Barrier and chemical warfare
• The skin is a water- tight barrier which helps to keep pathogens out.
• If they enter the body openings, then an enzyme called lysozyme in the tears, mucous, saliva, and urine kills microbes. Stomach acid kills most of the bacteria in food.
In the blood
• If pathogens make it through the skin, then phagocytes, which are patrolling white blood cells, attack and engulf them.
This is a macrophage and a lymphocyte, found in your blood that
wards off infection. It is homing in on a chain of nasty Streptococcus bacteria.
Lymphocytes
• On the outer surface of the pathogen are unique markers called antigens, which escape into the blood.
• White blood cells called lymphocytes absorb the antigens and release antibodies into the blood stream.
• The antibody recognises the pathogen that made the antigen and destroys it.
• As different pathogens make different antigens, there are many antibodies floating around in blood.
Immunity to Disease
• When you are first infected by a pathogen, they multiply rapidly causing symptoms of the disease.
• As antibody levels build up, the pathogens are killed.
• You then have an immunity to further infection by that pathogen, because you have antibodies in your blood that will recognise the antigens released by that specific pathogen.
Vaccinations• You can gain artificial immunity to disease, by being
injected with weakened or dead pathogens, which stimulate the lymphocytes to produce antibodies against them.
• If you then get infected by the living pathogen, you already have the antibodies which can deal with them. This is called a vaccination.
• Antibiotics are chemicals produced by fungi which are effective at killing bacteria. When taken, they kill pathogens without affecting the cells of the host.
• Bacteria develop resistance to a particular antibiotic through genetic changes known as mutations. They then multiply passing on the resistant gene to their offspring.
• http://www.brainpop.com/health/diseasesinjuriesandconditions/vaccines/
Antibiotic resistance
• Variation exists in all bacterial populations• Some bacteria possess a resistance to
antibiotics• In the presence of antibiotics these
bacteria have an advantage and can survive longer
• Improper use of antibiotics can lead to these bacteria building up in the population leading to antibiotic resistance
TB
• Tuberculosis is a common and deadly disease that generally affects the lungs
• Treatment of active TB requires taking a mixture of antibiotics for 6-12months
• Antibiotic resistant TB is an issue in less developed countries due to the cost and accessibility of the drugs
• As resistance increases more expensive drugs are required for longer periods of time.
Fighting viruses
• When we are infected with a virus our immune system detects the invaders and produces antibodies.
• Antibodies are proteins produced by white blood cells that help destroy pathogens inside the body
• Antibodies recognise antigens (markers on pathogens)
• The body holds a memory of the virus
Virus protein coats
• Viruses have a unique ability for escaping our immune system
• They can change/mutate their protein coats allowing them to go undetected by our memory cells causing us to show the symptoms of the illness
• This produces different strains of viruses and is the reason behind why we can have more than one flu or cold a year.
