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2. We know that the microorganisms
are livings things, but, What are
they? Are they harmful or useful?
What do they produce? We are
going to know about the world of
the microorganisms.

3. • Microorganisms are unicellular or
multicolour organisms, that are microscopic
(you can not see them with your naked eye).
Micro-organisms are classified into four major
groups;
 Bacteria;
 Fungi;
 Protozoa; and
 Viruses.

5. There are four main types of microorganisms. They
are :- bacteria, fungi, algae and protozoans.
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.
E.g. :- Algae – Chlamydomonas, Spirogyra etc.
Fungi – Bread mould, Penicillium,
Aspergilles etc.
Protozoans – Amoeba, Paramaecium etc.

10. Bacteria singular: bacterium) constitute a large
domain of prokaryotic microorganisms. Typically a
fewmicrometres in length, bacteria have a number of
shapes, ranging from spheres to rods and spirals.
Bacteria were among the first life forms to appear on
Earth, and are present in most of its habitats.
Bacteria inhabit soil, water,
acidic hot springs, radioactive waste,[2] and the deep
portions of Earth's crust. Bacteria also live in
symbiotic and parasitic relationships with plants and
animals. They are also known to have flourished in
manned spacecraft.[3]

13. A virus is a small infectious agent that replicates
only inside the living cells of other organisms.
Viruses can infect all types of life forms, from
animals and plants to bacteria and archaea.[1]
Since Dmitri Ivanovsky's 1892 article describing a
non-bacterial pathogen infecting tobacco plants, and
the discovery of the tobacco mosaic virus by
Martinis Beijerinck in 1898,[2] about 5,000 viruses
have been described in detail,[3] although there are
millions of different types.[4]Viruses are found in
almost every ecosystem on Earth and are the most
abundant type of biological entity.[5][6] The study of
viruses is known as virology, a sub-speciality

14. VIRUS

17. Protozoa are a diverse group of unicellular
eukaryotic organisms,[1] many of which are motile.
Historically, protozoa were defined as unicellular
protests with animal-like behavior, such as
movement. Protozoa were regarded as the partner
group of protests toprotophyta, which have plant-like
behavior, e.g. photosynthesis. The term protozoan
has become highly problematic due to the
introduction of modern ultra structural, biochemical,
and genetic techniques. Today, protozoan are
usually single-celled andheterotrophic eukaryotes
containing non-filamentous structures that belong to
any of the major lineages of protests.

20. A fungus plural: fungi[3] or funguses[4]) is any member of
a large group of eukaryotic organisms that includes
microorganisms such as yeasts and molds (
British English: moulds), as well as the more familiar
mushrooms. These organisms are classified as
a kingdom, Fungi, which is separate
from plants, animals, protists, and bacteria. One major
difference is that fungal cells have cell walls that
contain chitin, unlike the cell walls of plants and some
protists, which contain cellulose, and unlike the cell walls
of bacteria. These and other differences show that the
fungi form a single group of related organisms, named
theEumycota (true fungi or Eumycetes), that share
a common ancestor (is a monophyletic group)

23. • Micro-organisms may be single-celled like
Bacteria, some Viruses and some Protozoa, or
Multicolor, such as Virus and Fungi.
• They can survive under all types of
environment, ranging from ice cold climate to
hot springs and deserts to marshy lands.
• Microorganisms like amoeba can live alone,
while fungi and bacteria may live in colonies.

24.  In agriculture they are used to increase soil fertility by
fixing nitrogen.
 Milk is turned into curd by bacteria.
 Of these, the bacterium Lactobacillus promotes the
formation of curd. Bacteria are also involved in the
making of cheese, pickles and many other food items

25.  Microorganisms are used for the large scale production of
alcohol, wine and acetic acid (vinegar. For this purpose
yeast is grown on natural sugars present in grains like
barley, wheat, rice and crushed fruit juices, etc.
 The process of conversion of sugar into alcohol is known
as fermentation.

26.  Microorganisms are used in the production of
antibiotic tablets, capsules or injections such
as of penicillin.
 Such medicines are called antibiotics. These
days a number of antibiotics are being
produced from bacteria and fungi.
Streptomycin, tetracycline and erythromycin
are some of the commonly known antibiotics.

27.  When a disease-carrying microbe
enters our body, the body produces
antibodies to fight the invader.
 Children are given injections to protect
themselves against several diseases.
 Polio drops given to children are
actually a vaccine.
 These days vaccines are made on a
large scale from microorganisms to
protect humans and other animals from
several diseases.

28.  Some bacteria and blue green algae are able to
fix nitrogen from the atmosphere to enrich soil
with nitrogen and increase its fertility. These
microbes are commonly called biological
nitrogen fixers.

29.  Microorganisms are harmful in many ways. Some of the
microorganisms cause diseases in human beings, plants and
animals. Such disease-causing microorganisms are called
pathogens.
 Examples of such diseases include cholera, common cold,
chicken pox and tuberculosis.
 There are some insects and animals which act as carriers of
disease-causing microbes.
 Housefly is one such carrier.
 Examples of carriers are: the female Anopheles
mosquito which carries the parasite of malaria;
 Female Aides mosquito acts as carrier of dengue virus.

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32. Food poisoning is a common, yet distressing and
sometimes life-threatening problem for millions of
people in the U.S., and throughout the world. People
infected with foodborne organisms may be symptom-free
or may have symptoms ranging from mild
intestinal discomfort to severe dehydration and bloody
diarrhea. Depending on the type of infection, people
can even die as a result of food poisoning.
More than 250 different diseases can cause food
poisoning. Some of the most common diseases are
infections caused by bacteria, such as Campylobacter,
Salmonella, Shigella, E. coli O157:H7, Listeria, and
botulism.

34.  Boiling kills many microorganisms in milk.
Low temperature inhibits the growth of
microbes.
 The milk is heated to about 70 Degrees
Celsius for 15 to 30 seconds and then
suddenly chilled and stored. By doing so, it
prevents the growth of microbes. This
process was discovered by Louis Pasteur. It is
called pasteurization.

35. 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 salts and edible oils. Jams and
squashes can be preserved by using sodium benzoate,
sodium metabisulphite. These chemicals are called
preservatives.
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.
iii) By using sugar :- Food items like jams, jellies,
squashes etc. can be preserved by using sugar solution. It
prevents the growth of microbes.
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.
v) By heat and cold treatments :- Heating food items kills
microbes. Similarly storing food items at low
temperatures prevents growth of microbes.

36. Pasteurization :- The process of heating milk to
about 70oC 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.
vi) By storage and packing :- Many food items are
stored in air tight containers to protect them from
microbes.

37.  Rhizobium bacteria is involved in
the fixation of nitrogen in
leguminous plants (pulses).
Rhizobium lives in the root
nodules of leguminous plants ,
such as beans and peas, with
which it has a symbiotic
relationship.
 Sometimes nitrogen gets fixed
through the action of lightning.