MICROORGANISMS: FRIEND & FOE

MICROORGANISMS : FRIEND AND FOE

[Micron (µ) = 10 ^-6 m]   For VIDEO Chick the Link - [size compared]

1) Microorganisms (Microbes) :-

 i)  Microorganisms are very small organisms which cannot be seen with the unaided eye. They can be seen only with a magnifying glass or microscope.

ii) Microorganisms may be unicellular or multi-cellular.

iii) Microorganisms may exist alone or in colonies.

iv)  Microorganisms are found in all kinds of environment like ice cold climate, hot springs, deserts, marshy lands etc. They are also found inside the bodies of other organisms.

    

2) Types of microorganisms :-

   There are four main types of microorganisms. They are :- bacteria, fungi, algae and protozoa.

   Viruses are also considered as microorganisms. They are different from other microorganisms because they reproduce only in the body of host organisms like bacteria, plants or animals.

  Eg :-    Algae – Chlamydomonas, Spirogyra, Chara etc.
Click the link for Video- [ALGAE ]

CHLAMYDOMONAS (courtesy Google images)

SPIROGYRA (courtesy Google image)

CHARA (courtesy Google image)

              Fungi –  Bread mould (Mucor, Rhizopus), Penicillium, Yeast etc.
Click the link for VIDEO- [ FUNGI]

MUCOR Colony

MUCOR (Bread/ Black Mould)

Rhizopus (Green Mould)

Black and Green Mould on Bread (courtesy Google images)

PENICILLIUM

YEAST (Unicellular Fungus)

              Protozoa –  
                        Amoeba, Paramecium, Plasmodium (malaria parasite) etc.
Click the link for VIDEO- [ Amoeba eating Paramecium]

(Amoeba in Microscope)

(Paramecium under microscope)

(Blood Cells/Smear showing Plasmodium/ Malaria Parasite)

Virus:  Click the link to see Video:- [What are Virus?]

Generally they are not considered as microbes (though they are microscopic) as they are not organisms (neither living nor dead). Eg. Reterovirus (HIV, Hepatitis  B Virus), Corona virus (SARS, MERS, COVID-19), Bacteriophages (viruses that attack bacteria) etc..

Human Immunodeficiency Virus (HIV)

Corona Virus

BACTERIOPHAGE (courtesy Google images)

To know more on COVID-19 click on the you tube link (VIDEO)

3) Friendly microorganisms (Useful microorganis) :-

   i) Microorganisms  like bacteria decomposes organic waste into manure and increases the fertility of the soil.

  ii) Microorganisms help in fixing atmospheric nitrogen into nitrogen compounds in the soil and increases the fertility of the soil.

 iii) Microorganisms are used for making curd from milk, for making cheese, pickles, bread, cakes, pastries, alcohol, wine, vinegar (acetic acid) etc.

iv) Microorganisms are used for making medicines.

a) Making curd from milk :- click on the link to see [VIDEO]

The bacterium   called Lactobacillus reproduces in milk and helps to convert milk into curd.

Lactobacillus 

b) Making bread :-  The fungus called yeast reproduces in flour dough and produces carbon dioxide during respiration which makes the dough soft and helps in making bread, cakes, biscuits, pastries etc.

YEAST (unicellular fungus)

Yeast Powder in Milk Processing

c) Making alcohol :- 
The Fungus called yeast reproduces in sugar solution and converts it into alcohol. This process is called fermentation.

d) Making medicines :-  Some bacteria and fungi are used to make medicines which kill or stops the growth of disease causing microorganisms. Such medicines are called antibiotics. Eg :- streptomycin, tetracycline, erythromycin etc. (Amoxicillin now a days)

AMOXICILLIN (Antibiotic now a days)

    Vaccines are dead or weakened microbes introduced into the body to produce antibodies. These antibodies protect the body from disease causing microbes. Diseases like polio, cholera, typhoid, small pox, hepatitis etc. can be prevented by taking vaccines.

SMALL POX VACCINE

VACCINATION SCAR ON FOREARM

4) Harmful microorganisms :-

  i) Some microorganisms cause diseases in plants and animals. Such disease causing microorganisms are called pathogens.

 ii) Some microorganisms grow in food substances and produce toxic substances and makes the food poisonous. Food poisoning causes illness and even death. Bacteria Clostridium botulinum cause severe type of food poisoning called BOTULISM.

(Clostridium botulinum)

iii) Some microorganisms spoil materials like clothing, leather, wood etc.

(Fungus on Leather Mobile Cover)

5) Disease causing microorganisms in Humans :-

   Disease causing microorganisms enter our body through air, water, food, contact or insects. These microorganisms are called pathogens.

    Diseases which can spread from an infected person to a healthy person are called communicable diseases.

    Eg :- cholera, common cold, chicken pox, tuberculosis etc.

    Some insects and animals act as carriers (VECTORS) of disease causing microbes.

    Eg :- House fly, Female anopheles mosquito (malaria), Female Aedes mosquito (dengue fever) etc.

(Tiger Mosquito - Aedes egyptii)

(courtesy Google Images)

6) Disease causing microorganisms in plants :-

   Microorganisms cause diseases in plants like rice, wheat, potato, sugarcane, apple, orange etc. These diseases reduce crop yield. They can be controlled by using chemicals which kill the microbes.

(Plant Diseases)

Some common human diseases caused by microorganisms:-

           

(courtesy Google Image)

Some common plant diseases caused by microorganisms :-

          

Fungus (Phytophthora infestans) causing Late Blight in Potato/Tomato

(BACTERIAL BLIGHT OF POMEGRANATE)

FUNGUS (Collatrotrichum falcatum) cause RED ROT of SUGARCANE

        

(YELLOW MOSAIC VIRUS)

7) Food preservation :-

   Food is spoilt by microorganisms. Spoilt food has bad smell and bad taste and causes food poisoning. Food can be preserved by protecting it from microorganisms. Food can be preserved by different methods. They are :-

i)           Chemical method :- Food like pickles can be preserved by using chemicals like  metal salts and edible oils. Jams and squashes can be preserved by using sodium benzoate, sodium metabisulphite. These chemicals are called preservatives.

SCIENCE INVOLVED:  salts change the pH of the medium and makes it unfit for microbe to survive. Oils cut off the air supply by making a thin layer, hence removing oxygen for respiration.

(PRESERVATIVE-Sodium Benzoate)

To learn more about Sodium Benzoate click [ Here ]

ii)        By using common salt :- Food items like fish, meat, amla, raw mangoes, tamarind etc can be preserved by using common salt. It prevents the growth of microbes.

SCIENCE INVOLVED:  Common Salt (NaCl) makes the medium HYPERTONIC (strong solution) which cause plasmolysis (removal of water from body by exosmosis) and death of microbe.

(SALT LEMON PRESERVATION)

iii)      By using sugar :- Food items like jams, jellies, squashes etc. can be preserved by using sugar solution. It prevents the growth of microbes.

SCIENCE INVOLVED: Sugar makes the medium HYPERTONIC (strong solution) which cause plasmolysis (removal of water from body by exosmosis) and death of microbe.

(JAMS & JELLIES)

iv)       By using oil and vinegar :- Food items like pickles, vegetables, fish, meat etc. are preserved by using oil and vinegar. It prevents the growth of microbes.

SCIENCE INVOLVED:  Oils form a layer on the surface of food cutting off air. So microbes can’t respire. Vinegar contains acetic acid which kills microbes (changing the pH) and adds to the taste of food too.

(CUCUMBER IN VINEGAR)

v)         By heat and cold treatments :- Heating food items kills microbes. Similarly storing food items at low temperatures prevents growth of microbes.

SCIENCE INVOLVED:  Change in temperature affects the enzyme activity and hence the overall activity/ metabolism of microbes. Low temperature (Freezing) decrease/stops the multiplication rate of microbes while heat kill microbes and keep a check on their number in the food, hence increasing the life of food item.

(SMOKING OF FISH)

(INFRA RED HEATING OF FOOD)

      Pasteurization :- The process of heating milk to about 70^oC for 15 to 30 seconds and then suddenly chilling it to prevent the growth of microbes is called pasteurization. This process was discovered by Louis Pasteur.

(LOUIS PASTEUR- FATHER OF MICROBIOLOGY)

To learn details of Pasteurization click [ Here ]

i)           By storage and packing :-  Many food items are stored in air tight containers to protect them from microbes.

SCIENCE INVOLVED:  Airtight containers prevent oxygen to enter and kill microbes, but the caned/ tinned food must be sterilised first before keeping food for long.

( FOOD PACKAGING)

To know more  about food  poisoning and preservation see the VIDEO by clicking on [ FOOD POISONING & PRESERVATION]

8) Nitrogen cycle :-

By volume, dry air contains 78.09% nitrogen in it. Nitrogen is also an integral component of living cell (eg. Amino acids of protein) and as mineral/other forms  in soil eg. Nitratine (sodium nitrate), Nitrobarite (barium nitrate) etc..

Nitrogen cycle :-

1.     The nitrogen in the atmosphere is converted into nitrogen compounds in the soil by nitrogen fixing bacteria (eg. Rhizobium leguminosarum  and blue green algae.

(Bacteria RHIZOBIUM in the ROOT NODULES of plants)

2.     Lightning also converted into nitrogen compounds in the soil. The nitrogen compounds in the soil is used by plants for the synthesis of proteins and other compounds.

3.      Animals feeding on plants get these proteins and other compounds.

4.      When plants and animals die, bacteria and fungi in the soil converts the nitrogenous waste into nitrogen compounds in the soil which are again use by plants.

5.     Some other bacteria convert some nitrogen compounds in the soil into nitrogen gas which goes back into the atmosphere.

(NITROGEN CYCLE)

(NITROGEN CYCLE -SIMPLIFIED)

Hence the nitrogen in the atmosphere almost remains constant.

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