MICROBIAL WORLD-13 (Autosaved).doc

7/30/2019 MICROBIAL WORLD-13 (Autosaved).doc

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MICROBIAL WORLDTHE STORY OF MICROORGANISMS

Let us think over following questions.

Why do we add some drops of butter milk to lukewarm milk while makingcurd?

Why does even cooked food get spoiled after some days?

Why do we get bad smell from our mouth after we wake up in themorning?

In this chapter we will try to find out what may be involved in causingsuch changes.

Years back several people wondered over such questions and tried to findout answers of such questions.

One such example is about Anton van Leeuwenhoek.

Story of Microscope invention and discovery of microorganisms

Anton van Leeuwenhoek single lens powerful microscope

Microbiology as a science was born in 1674 when Anton vanLeeuwenhoek peered at a drop of lake water through a glass lens that he hadcarefully ground. Anton van Leeuwenhoek was a fabric merchant. Leeuwenhoek

built a single lens powerful microscope, which can magnify the object 300 times.His curiosity and skill of making powerful lenses were the secrets of thisinvention of powerful microscope. His keen observation of different things under his microscope helped him to discover smallest moving organisms in 1678. Hecalled them as animalcules, later which were named as bacteria. Along withanimalcules he observed many other microorganisms under his microscopewhich got their respective names later on. This helped further discovery of other microorganisms.

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Now let us see what are Microorganisms and where we can find them.

Microorganisms

We can see some organisms with our naked eyes, like plants and animals around

us. But some organisms are so small that we cannot see them with our nakedeyes. We can see them only with help of a microscope. They are called asmicroorganisms. Some of the microorganisms are shown in Fig.2.1 to 2.5

Bacteri of different shapes Lactobacillus

Fig.2.1Bacteria as seen under Electron microscope

: Penicillium Bread mould Rhizopus Aspergillus

Fig.2.2 Fungi

Amoeba ( 500 Microns ) Paramecium ( 0.25m.m )

Fig.2.3 Protozoans

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Ceratium

Chlamydomonas Spirogyra Spirulina

Oedogonium Vorticella Osillotoria

Fig.2.4 Algae

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cylapse DaphniaScabies mite Eyelash mite


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Fig. 2.5 Micro Arthropods

Groups of microorganisms

Let us study some major groups of microorganisms. They are bacteria, fungi,

protozoa, algae and certain micro arthropods.To study these major groups we will do some activities.

For this we will need a Microscope. You already know how to use it. Youcould also refer to class VI Chapter and class VIII Chapter --

Activity 1 : Collect some pond water / or water from any tank in your surrounding. Ensure to take some of the greenish scrapings from sideof the tank. Take 1-2 drops of water (from the sample you have collected) on aslide and observe through Microscope. Draw rough sketches in your note book of what you observed. Take the help of given figures on page --- for observationand identification (you may also discuss with your friends). Take the help of your teacher as well.

Help Box

Can you name the organisms you have observed through the microscope?

We will try to know more about the microscopic world by doing the followingactivities.

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Photographs of microbes in pondwater, ex:Spirogyra,paramecium,


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Observing Fungi

Usually after the rainy seasion you may have seen some small umbrella likegrowths over rotten materials of dumped wast beteen the grasses in a field or edges of wet rotten wooden planks. Often you may have observed white patcheson the bark of trees. These are a few types of fungi. Now let us look at them more

closely by the following activity.Activity 2: Take some rotten part of vegetable or black spoiled part of bread or coconut with help of a needle on a slide. Put a drop of water, cover with a cover slip and observe through microscope.

Draw rough sketches in your note book of what you observed. Take thehelp of help box for the same.

Help Box

Observing Bacteria

We can see these in butter milk or curd or early morning scraping of tongue(before washing the mouth). We can also find them in the soil, over bark of trees,over our skin and many other places. But they are not visible to the naked eye.

Now let us look at them more closely by the following activity.

Activity 3:

Take one or two drops of butter milk on a slide, spread it on the slide. Heat itslightly on a lamp (3-4 seconds). Add a few drops of cristal violet on it. Leave itfor 30 to 60 seconds and wash the slide gently with water. Observe the slideunder the compound Microscope. Draw rough Sketches in your note book of what you observed. Take the help of the given help box for observation.

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ex.Rhizopous


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Help Box

Picture of actual observation of lactobacillus

Photographs of curd in bowlLactobacillus bacterium

Observing Algae

We observe greenish pond water in our surroundings. This greenishness is because of growth of Algae and other plants in water. We can see some of algaewith naked eye like chora, but most of the algae present in water is also

microscopic. They can be observed only through a microscope. Let us collect pond water or water from the tanks with bit of greenish scrapings. To observesome of the micro algae growing in water let us do the following activity.

Activity

Take one or two drops of collected greenish pond water (in a bottle) on aslide. Cover it with a cover slip and observe through microscope . Draw roughsketches in your note book of what you observed. Take the help of help box for

the same.

Do you know?There are several Bacteria growing on our skin. Many of the disease

causing ones live in some symbiotic relations with other bacteria. There are severaltypes of them in our body as well. We cannot do without the bacteria present insideour intestine.

Bacteria are found everywhere and there are over thousand types of themin soil, water etc. Recently two types of bacteria nearly a millimetre long were

discovered which can be seen with naked eye.

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Observing Protozoa

Some of other group of microorganisms are protozoans. Most of the protozoans present in the water and soil. We can see them through microscope only. Let usdo the following activity to observe them.

Activity

Take one or two drops of hay decation water on a slide and observe under themicroscope . Draw rough Sketches in your note book of what you observed. Takethe help of the given help box for observation.

Microorthropods

We can see some arthropods with our eyes such as Ants, Cockroaches,Scorpions, etc. But some arthropods are microscopic which are known as micro

arthropods. Some micro arthropods are very important in soil which helps in soil

Do you know?

Micro Algae photosynthesis is important for life on earth. They produce

approximately half of the atmospheric oxygen and use green house gase carbondioxide. The bio diversity of Micro Algae is enormous. It has been estimated thatabout 2 lakhs to 8 lakhs species exist.

Do you Know?

To grow protozoans prepare dication of hay and take in a bowl and add somecollected pond water to it. After 3- 4 days take drop of water and observe under

compound microscope. You can also add some boiled bendi pieces to the heydication.

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fertility by decomposing the biomass through disetion which converts the bigger compounds in to smaller compounds.

Some micro arthropods cause diseases like scabies e.g.: scabies mites.

Observing soil microorganisms

Do you know?

Soil is highly rich of microorganisms such a bacteria, fungi,Actinomyceties, protozoans, microorthropods. The top of eight inch soil of oneacre may contain as much as five and half tons of fungi and bacteria. We can seethem trough microscope only, by growing them in different media. Let us dofollowing activity to observe some of soil microbes.

Activity 4: Collect some soil from the field in a beaker or in a glass .Add somewater to it and stir it. Wait for some time to let the soil particles settle down. Takea drop of water on a slide and observe under the Microscope. Draw roughsketches in your note book of what you observed. Take the help of help box for

observation.

Help box

Photographs and ex. Of soil micro orgsanisms microorthropodmites, worms, fungal, spores, fungal hyae.

Help Box

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Photographs and ex. Of soil micro orgsanismsmicroorthropod mites,worms, fungal, spores,fungal hyae.


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Do you know?

To grow soil microbes we must add 2-3boiled cucumber pieces to thesoil mixed water and keep it for there to four days. Observe on the cucumber

pieces. Take little part of Cucumber piece and observe under Microscope. Takehelp of your teacher.

From the above activities you would be able to understand the diverseness of the microorganisms. You can also appreciate the fact that this is another amazingworld of living organisms.

Let us try to find out where else we can find them.

Where are microorganisms present?

Microorganisms present everywhere around us. They present in air, water,soil. They are also present inside and outside of animals including human beingsand on plants. They can survive in all types of environments ranging from icecold climate to hot springs, deserts to marshy lands. Some microorganisms growon other organisms ( parasites) and some may exist independently like algae

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Diseases like typhoid, tuberculosis (T.B) and septicaemia (blood poisoning)caused by bacteria. Some of the skin diseases are caused by fungi while others bymicroorhropods and bacteria. Diseases like Malaria, Amoebiasis are caused byProtozoa (Protozoans )

Are Microbes (Microorganisms) our friends or foes?

As you came to know that microorganisms present everywhere, think whether these microorganisms are helpful like our friends? Or microorganisms do harmlike our foes? Yes, some microorganisms are very useful and help us. But someof microorganisms are very harmful. They cause diseases and spoil our food.

Now let us we study about them in detail.

Do you know?Viruses are very interesting type of microorganisms. They behave like non living

things when they are outside of a living cell. But they behave like living organisms byreproducing in host living cells like bacteria, plants or animals. They can only be seenthrough very powerful electron microscope. Some Viruses are shown in Fig-2.5.

HIV

Fig.2.5 Viruses

Diseases like polio, swine flu, conjunctivitis, smallpox, chickenpox and AIDS arecaused by viruses.

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USEFUL (FRIENDLY) MICROORGANISMS :

Some microorganisms are very useful in everyday life, for example in curdmaking and in preparation of idly and dosa. Some are useful in preparation of Bakery bread and cake. Some microorganisms are very helpful in curingdiseases (in the form of antibiotics). Some microorganisms prevent very harmful

diseases (in the form of vaccines). Some are former friendly by increasing soilfertility by nitrogen fixation. Some are helpful in cleaning the environment, byconverting organic wastes. They degrade them into small nutrients and convertthem into organic manure.

ACTIVITY: Take some lukewarm milk in two small bowls. Add few drops of butter milk or little curd in one of the bowls. In the second bowl do not addanything. Keep the bowls at warm place and observe the milk in the bowls after 5 to 6 hours. What changes did you observe? And think what the reason is?Discuss with your friends.

Photographs of curd making

Curd or buttermilk contains bacterium named lactobacillus . Lactobacillusconverts the milk into the form of curd. Curd is easily digestible, will have goodtaste and smell.

ACTIVITY: Take 100 grams of Myda flour in a bowl, add one or two spoonsof yeast powder, some water and knead it to make dough. Keep the dough in awarm place. Observe the dough after 3-4 hours. What changes you have observedin the dough? What might be the reason? Think and discuss with your friends.

You might have observed in your home your mother preparing fermented foodlike idly, dosa.

Myda dough in two cups but one is mixed with Yeast. Which one?

Can you fiend?

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In making bakery bread and cake, fungus yeast is added, which ferments the bread. Yeast produces carbon dioxide. Bubbles of the gas fill the dough andincrease its volume and become spongy in nature, so this is the main reason for using Yeast in bakery industry in making bread and cakes. Yeast producesvitamin B. So bakery bread is also one of the sources of vitamin B.

Microorganisms help in fermentation in preparing idly and dosa.Commercial use of microorganisms

ACTIVITY: Take half glass of water, in two beakers or bowls separately. Add5 to 10 spoons of sugar in the water, and add 2 to 3 spoons of yeast in one of the

bowls. Close the bowls with lids, and keep them in a warm place. After 3 to 4hours remove the lids and smell. What difference that you have observed in two

bowls? Think what might be the reason?

PHOTOGRAPHS

This is the smell of Alcohol. Sugars are converted in to Alcohol by yeast.This process of conversion of sugars into Alcohol is known as fermentation.This process is used in the large scale production of alcohol, wine, beer andacetic acid. For this yeast is grown in natural sugars present in grains like barley,wheat, rice and crushed fruit juices like grapes.

In sugar industry molasses is produced. It is used in preparation of ethylalcohol by fermentation process by adding yeast.

PHOTOGRAPHS

Medicinal use of Microorganisms

Sometimes we may fall ill, with fever like typhoid or cough. Sometimes someof us may be injured or needed an operation. In all these cases doctors prescribeus some medicines (antibiotics). We take these medicines, in the form of syrups,tablets or injections. Some of these medicines kill or stop the growth of diseasecausing microorganisms like bacteria. Such medicines are called antibiotics. Bygrowing specific microorganisms these antibiotics are produced. Nowadays

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Do you know?

Consuming alcohol effects on functioning of our digestive system andCentral Nervous System i.e. which harms our health.


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number of antibiotics like penicillin, Tetracycline, streptomycin andErythromycin are made from fungi and bacteria. Antibiotics are helping us bycuring many bacterial diseases like Typhoid, Gonorrhoea and prevent infectionslike Septicaemia i.e. blood poisoning.

Antibiotics help animals also in curing bacterial diseases like Anthrax, andchecks bacterial infections. They are also used to control bacterial diseases in

plants.

Do you know?

We must use antibiotics with prescription of a qualified doctor only for the prescribed period. If you use antibiotics without consulting a qualified doctor which may harm you. Unnecessary use of antibiotics effects leucocytes( W.B.C ), which are natural protectors of our body from diseases .Sometimesthey may kill useful bacteria in you.

The story of discovery of Penicillin

Dr. Alexander Fleming was an army doctor in First World War. He observedmany injured soldiers died because of bacterial infection of wounds. He wasworking on antibiotics in his lab. One day he keenly observed some mould is

preventing the growth of bacteria in the Petridis in which he culturing bacteria.

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He separated the fungus and tested on some other disease causing bacteria.Which also killed the other disease causing bacteria. The mould or fungusseparated was identified as penicillium notatum. The substance which produced

by the fungus penicillium is named as Penicillin. The discovery of penicillinantibiotic published in 1929. In 1945 Dr. Alexander Fleming was awarded Noble

prize along with Dr.Howard flory, and Dr. Ernst.B.chain for the discovery of penicillin antibiotic, which cured many bacterial diseases and prevented bacterialinfections. The discovery of penicillin paved the way to discover of manyantibiotics like streptomycin, Erythromycin from fungi and bacteri

Story of discovery of Smallpox vaccine :

The decision of Dr. Edward Jenner to setup his medical practice incountry yard i.e. in a village, which helped mankind save from extinction fromdiseases with discovery of vaccines. He keenly observed that the milkmaids whodeveloped cowpox, a less serious disease, did not develop the deadly smallpox.He thought they are developing immunity which is preventing small pox which a

very dangerous disease wiping out millions of people in those days. In 1796,Jenner took the fluid from a cowpox pustule on a dairymaids hand and

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Do you know?Inventor of Aureomycin

Dr.Yellapreggada Subba Rao

He belong to our India particularly to our AndhraPredesh State.

He discovered Aureomycin i.e Tetracycline which cures number of bacterialdiseases like Typhiod, plague, Tuberculosis etc.


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inoculated a 8 years old boy with his parents permission. Six weeks later, heexposed the boy to smallpox, and the boy did not develop any symptoms of smallpox. This invention of smallpox vaccine saved millions people from deadlydisease. This showed the way for the discovery of number of vaccines which

prevent us from harmful diseases. Vaccine term came from vaca means cow.

VaccineHave you listened that children below five years must take polio drops? Whychildren should take polio drops? What is the use of polio drops? Have you taken

polio drops? Think and discuss with your parents and friends.

When disease causing microorganisms enters in to our body, our body

reacts and produces antibodies. Antibodies fights with disease causingmicroorganisms. If antibodies produced are more in number the disease causingmicroorganisms are eliminated. Then there will be no disease. If antibodies

produces are less in number than disease causing microorganisms and further increases their number by reproducing. The diseases like polio, smallpox, etcdevelops gradually.

Even when killed or weakened microorganisms enters into our body, inthe same way above our body reacts and produces antibodies. Which are more innumber ready to fight. When the disease causing microorganisms enters in our

body , the already present antibodies fights and eliminates the disease causingmicroorganisms. Thus the disease is prevented. The killed or weakened diseasecausing microorganisms which will be given to us is called vaccine. Poliovaccine is given in the form of oral drops which prevents polio in children.

Numbers of vaccines are developed to prevent diseases like typhoid, smallpox,chickenpox, Cholera, hepatitis, Tuberculosis, etc.

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Nowadays vaccines are made on a large scale from microorganisms to protecthuman and other animals from several diseases.

Activity: Meet a doctor or a health worker and ask what types of vaccines arethere? Which disease can be prevented? When it should be taken? List them out.

MICROORGANISMS IN SOIL FERTILITY :

Nitrogen is an essential element to grow plants. Nitrogen is an importantcomponent of proteins. Most of the air consists of Nitrogen gas (78%) . Plantscannot take atmospheric Nitrogen directly. Some microorganisms like blue greenalgae, Rhyzobium bacterium which present in the fruit nodules of legumes can

fix atmospheric Nitrogen. Thus blue green algae like Nostac and Anabaena,

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Have you listened to a saying?

PREVNTION IS BETTER THAN CURE

Do you know?

Dr. Jonas Salk discovered vaccine for Polio in 1952. He wanted todistribute it freely to everyone. So he never patented his polio vaccine. Dr.Albert Sabin discovered oral polio vaccine in 1957.

Do you know?

Vaccine for Rabies was discovered by Luis pasture. Rabies causingvirus enters in to our body through Rabies infected dog bite.


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bacterium like Rhyzobium helps in soil fertility. We know that soil fertility helps plants to grow well.

Figures : Nostoc Anabina

The micro organisms present in the soil like fungi and bacteria degrade biological wastes present in the soil into small nutrients. Small nutrients areessential to plants to grow.

Do microorganisms clean our environment?

ACTIVITY: Take two pots or dig two pits in a corner of waste place in your ground. Fill them half with loose soil. Put some biological wastes like fallenleaves, vegetable wastes, waste papers etc., in one of them. Fill the second onewith plastic wastes, polythene bags and with some empty glass bottles. Nowcover the pits or pots with some loose soil. Sprinkle some water on the pots /pits.Do this every day. After three to four weeks remove the upper soil from the pitsand observe the changes. What changes you have observed? Note them down.

Think and discuss with your friends.

Compost pit

You might have often seen fallen leaves, fruits under the trees, some deadanimals in your surroundings. After some days or weeks can you see themagain? No, they might have gradually disappeared. How it was happened?Microorganisms present in the soil, air and water acts upon them anddecomposes. They are converted into simple substances. Thus microorganismshelp us in cleaning the environment.

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Do You Know?

Some of Microbes are used in Bio Technology. Transfer Of Genes from one Cell to another takes Places with the help Some Bacterium. Eg :

E.Coli, Agrobacterium tumifacians which were called as gene vectors( i.e.plasmid of the bacteria).

Do you know?

Which microorganisms help in sewage treatment?

Do microorganisms harm us?

Activity: Meet a doctor nearby you, with the help of your teacher or parents.Ask the doctor what are the different types of diseases, caused by different micro

organisms and note them down and discuss with your friends.

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Think

What would happen if microorganisms are absent, in our surroundings? What might be present in our surroundings?

Do you know?

Some Bacteria present in our intestine helps us in digestion.

DO YOU KNOW?

What is Bt?

Bt means Bacillus thuringiensis is name of a bacterium. It produces a toxin which

kills pests on plants or crops. The bacterium is used as bio pesticides.In transgenic crop plants this toxin produced gene was separated from the bacterium

and transferred into the crop plants. So this can protect it from pests. For exampleB.T. cotton.


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Harmful microorganisms:

We have already studied about useful Microorganisms. Now let us learn about

harmful Microorganisms which spoil food, clothes and cause diseases to plantsand animals.

Diseases causing microorganisms in human beings:

Recall that microorganisms are present everywhere in our surroundings.Microorganisms which cause diseases are called them as pathogens. Pathogensenter into our body through air we breathe, through water we drink and food weeat. They can also be transmitted by the direct contact with infected person or

carried through animals or insects. When these pathogens enter into our bodyand causes diseases.

You might have observed, sometimes some of our (your) family members or friends may get cold and cough at the sudden change of weather. When theinfected person sneezes or coughs, the pathogens enter in to the air from infected

persons. This air containing pathogens enter into the healthy persons body, anddevelops cold. This type of diseases which spreads from infected people tohealthy persons is known as communicable diseases. Communicable diseases

spread through air, water, food or through physical contact of infected person (or his used towels, kerchiefs) or through insects like houseflies and mosquitoes.Common cold, conjunctivitis, typhoid, smallpox, chickenpox, swine flu,Tuberculosis are some communicable diseases.

Anopheles female mosquito biting Malaria causing Plasmodium

Some insects and animals carry diseases causing microorganisms. They arecalled as vectors. The microorganism plasmodium causes malaria.Plasmodium is a protozoan female Anopheles mosquito carries plasmodium.Female Aedes mosquito carries dengue virus. When these mosquitoes bitesmalaria, dengue infected persons, the microorganisms enters into thesemosquitoes. When they bite again a healthy person, the malaria causing

plasmodium or dengue causing virus enter into healthy persons body. Thusmosquitoes are vectors for malaria, dengue, chickungunya and brain fever

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(meningitis). How can we control or prevent these diseases? By controllingmosquitoes, mosquito bites we can prevent these diseases. All mosquitoes breedin stagnant water. We should be careful not let water collect anywhere in our surroundings, including left over waste pots, waste flower pots, tyres, bowls etc.,

HOUSE FLY ON FOOD

House flies also carry diseases causing microorganisms like typhoid,cholera. When they sit on garbage, excreta of infected persons or animals

pathogens stick to the body. When these flies sit again on a uncovered food, theytransfers the disease causing bacteria into the food. Whoever eats this food mayhave chances to get these diseases. So we must avoid taking uncovered food.We must always cover the food. Houseflies breeds on garbage. We can controlhouseflies by keeping our surroundings clean.

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Do You Know?

Dr.Ronald Ross discovered that female Anopheles mosquitoes was carrier of the causative Microorganism (parasite) for Malaria. For this discoveryDr.Ronald Ross got Nobel prize 1902. He discovered it in Secendrabad.

For full story of discovery of Ross go to Read and Enjoy section .................


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One day Srikanth went to hospital with his mother there he saw the followingchart on a wall.

TABLE : SOME COMMON DISEASES CAUSED BYMICROORGANISMS IN HUMAN :

Name of thedisease

CausativeMicroorganism

Mode of transmission

Preventive measures

Tuberculosis Bacteria Air * Vaccination

* Avoid using infectedpersons towels, Handkerchiefs, Glasses etc

Chicken pox Virus Air * Vaccination

Measles Virus Air * Vaccination

Polio Virus Air, Water * Vaccination

Swine flu Virus Air * Vaccination

Cholera

Typhoid

Bacteria

Bacteria

ContaminatedWater, Food

Contaminatedwater, Food

* Personal hygiene andgood sanitary habits

* Consume boileddrinking water

Malaria protozoa Mosquitoes * Use mosquito nets,repellents.

* Control breeding of mosquitoes by notallowing waterstagnation in oursurroundings

Dengue virus Mosquitoes ,,Chikungunya virus Mosquitoes ,,

Meningitis /JapaneseEncephalitis

Virus Mosquitoes

,,

Study above table and answer following questions.

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1.What diseases can be prevented if we can control Mosquitoes or Mosquitobites?

________________________________________________________________

2. Which diseases we can prevent by taking Vaccination? ________________________________________________________________

3. What are the diseases which transmits by contaminated water?

4. Can you name some diseases which transmits by Air?

________________________________________________________________ Disease causing microorganisms in animals

Microorganisms not only cause diseases in human beings but also in animals,and plants. Some examples are like Anthrax mainly in cattle and as well as inhuman .

Anthrax disease in sheep

Disease causing micro organisms in plants:Microorganisms also cause diseases in plants like rice, wheat, sugarcane,

groundnut, oranges, citrus and others. The diseases reduce crop yield. Certainchemicals and measure are used to control these diseases.

TABLE -------- shows some of plant diseases, causative microorganisms and

mode of transmission.

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Name of the

plant disease

Causative

Microorganism

Mode of

Transmission

Figure

Citrus canker Bactria Air

Red rot of sugarcane

fungi Air, seedlings

Tikka diseaseof groundnut

Fungi Air, seeds

Tobaccomosaic Virus Insects

Food poisoning:

Sometimes you might have listened or seen in news papers that some peoplehospitalised due to food poisoning. Food poisoning could be due to theconsumption of spoilt food. Some microorganisms produce toxic substances infood. These toxic substances make the food poisonous. If we take this food whichmay lead to vomiting, motions, even may death.

Food preservation:If microbes grow on our food, they spoil it. Spoilt food emits bad smell and

had bad taste. Water or moisture present in food items helps the microorganisms

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Do you know?Clostridium botulinum a bacterium causes food poisoning. The disease is

known as botulism.


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to grow. How can we preserve our food? We knew the cause of food spoilage i.e.growing of microorganisms. Think how can we prevent the growth of microbeson food?

You have learnt in 6 th class different methods adopted to preserve food at your home. For example while pickles making salt and oil is added. Fishes are

preserved by adding salt or smoking them. Jams and Jellies are preserved byadding sugar after boiling them. Vegetable slices are preserved by drying in hotsun light. What happens in all these methods? Think, water or moisture isremoved from the food items, Microbes cannot grow in these conditions.

Let us study some other methods of food preservation.

Heat and cold method

You might have observed that your mother boiling the milk before using or storing. Boiling helps in killing the microorganisms present in the milk. After lunch or dinner we preserve our remaining food items in refrigerator. We

preserve vegetables and some other food items in the refrigerator.

How food items wont spoil in refrigerator? Think, low temperatureinhibits the growth of microorganisms. Thus food is preserved in refrigerator andin cold storages.

Pasteurisation

Have you seen dairy milk is preserved in packets for a long time? How can beit preserved for long time? The dairy milk also called as pasteurised milk. Themilk is heated up to70 degrees C for 15 to 30 seconds and then suddenly chilledand stored. This prevents growth of microorganisms. This process is discovered

by Louis pasture . So this method is known as pasteurisation.

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PASTEURISATION PROCESS USED IN DAIRY TO PRESERVE THE MILK

Story of invention of pasteurisation

LOUIS PASTURE

Louis Pasture was born in a village of France in 1822. He obtainedintense patriotism from his father. He was also a painter. He wanted to become ateacher. But his interest was also in mathematics, physics, and chemistry. But heturned in to research. He was doing his research on crystals. Wine industry inFrance was in trouble with spoilage of preserved wine. They approached Pasture.Pasture studied the problem and hypothesised microorganisms may be cause of wine spoilage. He thought that these microorganisms can be controlled by heat.This led the invention of Pasteurisation. He proposed germ theory of diseases i.e.Microorganisms causes diseases. He invented vaccine for Rabbis which transmits

by bite of a rabbis infected dog. He studied and conquered Anthrax. He studiedgangrene, blood poisoning and showed how to control them.

Storage and packing

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Do you know?

Lazzaro Spallanzani?

He is the first person to prove experimentally microorganismscould be killed by boiling. (1768 ).


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Nowadays dry fruits and even vegetables are sold in sealed and air tight packets,which prevents entering microbes from outside.

Thus proper preservation of food helps us, in the fallowing ways:

1) This prevents spoilage of food.

2) We can preserve food for longer period.

3) Quality of food is preserved for long time.

4) Variety of food items may be available in faraway places, at any seasons.

NITROGEN FIXATION :

Root nodules of legume plant Rhizobium bacterium

ACTIVITY: Take root nodules of any pulses or leguminous plants crush it on

slide, put a drop of water, any oil on it and observe under microscope. What youhave observed? Draw the diagrams/note it down. Discuss with your friends.

You have learnt about rhizobium bacterium previously. Rhizobium which present in the root nodules of many leguminous ( pulses) plants. Such as beansand peas. The bacterium rhizobium absorbs atmospheric nitrogen and gives it tothe plant. Plant gives shelter and required food to the bacterium. Thus both help

each other. This relationship is known as symbiosis . Thus rhizobium helps insoil fertility. While farming crop rotation i.e. Growing of pulses plants helps toincrease in soil fertility.

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Do you know?Invention of pasteurisation led to the invention of sterilisation process.

In this process microbes are killed. In this process the materials were kept insterilisation chamber and heated up to high temperature upto 30 minutes.

While doing operations doctors uses sterilised instruments and other sterilisedmaterial, which avoids infections to patient wounds.


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What we have learnt? Microorganisms are very minute. We cannot see them with our naked eye.

We can see microorganisms with help of Microscope.

Microbes present everywhere in our surroundings.

Bacteria, Fungi, Protozoa, and Algae are major groups of microorganisms.

Viruses are special type of microorganisms, which stands between living andnon living organisms. They can reproduce only in host living cell.

Some Microorganisms are useful and some microorganisms are harmful.

Microbes are useful in home, industry, Medicine and cleaning the environment.

Microbes degrade organic wastes into nutrient manure. This helps in plantsgrowth.

Some microorganisms cause diseases in human, Plants, and other animals.

Some insects and animals acts as vectors of microbes.

Some microbes release toxins in improperly preserved food, which causes food poisoning.

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DO YOU KNOW?

BACTERIAL STAINING

Bacterias are very small/tiny microorganisms. We must stain before seeingBACTERIA UNDER MICROSCOPE . Smear bacteria on a slide and slightly heat theslide. Then put drops of crystal violet on the slide, after 30 to 60 seconds gentlywash the slide. Dry the slide and now watch the slide under the microscope in 25X or 40 X.

KEY WORDS

Microorganism , Microscope, Bacteria, Fungi, Protozoa, Algae, Virus,

Yeast, Fermentation, Antibiotics, vaccine, Plasmodium, Vector,Lactobacillus,Food poisoning, Food preservation, Nitrogen fixation.


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Pasteurisation process helps in food preservation.

Rhizobium bacterium which present in root nodules of legumes fixesatmospheric Nitrogen.

Improve your learning

1. Collect more information about scientists who invented and discoveredother facts related to Microorganisms. How these discoveries helpedmankind? What was the influence of these discoveries in further discoveries? Make a chart presentation and past it at your classroom wallMagazine.

2. Make a Album of scientists and their discoveries related toMicroorganisms.

3. Take three bowls and mark as A, B, C. Put some Luke warm milk in A bowl, pour some boiling milk in B bowl, Pour cold milk in C bowl. Addone tea spoon of curd or butter milk in three bowls and stir them slightly.Cover the bowls with lids. Keep the bowls undisturbed for five to sixhours. Think and guess in which bowls milk will be converted into curd

first, second, and third. Observe the changes in the milk in the Bowles A,B, C after 5-6 Hours. Note your guess and results in the following table.

Photographs:

Table: Which bowl of the milk is converted in to milk 1 st, 2 nd, 3 rd

Bowl A Bowl B Bowl C

Your guess

Your experimental

Result

Analyse the results. Think for the reason, and note them down. Discusswith your friends.

4. Take two water bottles or two test tubes fill quarter of them with water.Add five to six tea spoons full of sugar in each of the bottle. Add two to

three spoons full of Yeast in one of the bottle only. Take two balloons tie

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them to the mouths of the bottles. Keep the bottles at warm place for 3-4hours. Think at what would happen? Record your observations? Also try tofind out the reason behind these observations.

Now take another water bottle, pour some lime water. Remove swollen balloon and fix it to the lime water containing bottle. And shake well thelime water, while pressing the balloon to send the gas in to the lime water

bottle. Observe the changes in lime water and note them down. Think for the reason for the changes you have observed, note them down and discusswith your friends.

Photographs:

5. Prepare an exhibit on Useful Microorganisms and put them in your schoolscience exhibition.

6. Prepare an exhibit on harmful Microorganisms and put them in your schoolscience exhibition.

7. Visit any disease diagnostic centres or labs with help of lab technicianobserve some pathogenic microorganisms.

8. Visit pathology Department in any Medical college nearby you with help

of your teacher or parent. And request the professor about further information about pathogenic Microorganisms and their investigationmethods.

9. Visit any Dairy and know how pasteurisation of milk takes place?

10. Meet any Agriculture scientist and request him for further informationabout Bio fertilisers and Bio pesticides. How are they useful inAgriculture?

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11. Visit any Agriculture University or any Agriculture Research Centre andrequest the scientist about B.T crops? How are they useful for formers?What are the other effects? And discuss in your class.

12. Visit any Microbiology department of Degree, PG College or Universitynearby you with help of your teacher or parents .Know some techniques to

culture some Microorganisms from air, water, soil and from rottenvegetables or fruits.

13. Prepare one Bacterial or Fungal medium with help of your teacher andgrow some bacteria or fungi in them and observe the appearance andcolour of these.

14. Observe some useful and harmful microorganisms on prepared permanentslides with help of Microscope, and note them down.

15. Which one is better to take Antibiotics or vaccines? Why?16. Refrigerator helps us in saving health and money. Can you explain?

17. What are antibodies? When do they develop? How they help us?

18. Can we prevent diseases? How?

19.Prevention is better than cure How Can you correlate it withMicroorganisms?

20. Do you know the story of the discovery of Malaria causative organism? Whoand where it was discovered?

21. Raheem is telling to his neighbours stagnation of sewage in our surroundingsis harmful to our health. Can you explain this?

22. Can you give some important key points you noticed Scientists followed intheir inventions and discoveries?

23. Which invention is most important related to Microorganisms? Can you

explain the reasons why it is so important?24. One Medical store owner is giving antibiotics to his customer who issuffering with fever without doctors prescription? But customer daughter Malathi is telling her father not to take antibiotics without doctors prescription.Whom do you support and why?

25. Latha is telling his little brother Rajesh to gargle his mouth with water after eating chocolates, ice creams and any other food. Is Latha correct? How can yousupport her?

26. What are the differences between Antibiotic and Vaccine?

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27. Anil went to Jathara along with his family. His father wants to buy somefood in a shop. Anil observed many house flys are moving and sitting on thatfood. Anil is telling to his father dont buy uncovered food? Why we should not

buy uncovered food? How it is Harmful? Think and discuss with your friends. Note them down,

Do you know?

PREVNTION IS BETTER THAN CURE

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Documents

MICROBIAL WORLD-13 (Autosaved).doc