2. INTRODUCTION TO MICROORGANISMS
A microorganism or microbe is an organism
which is microscopic, which means so small
that people cannot see them with naked eye.
The study of microorganisms is called
microbiology. Microorganisms include
bacteria, fungi, algae, protozoa and viruses,
and are among the earliest known life forms.
3. CHARACTERISTICS OF MICROORGANISMS
• Microorganisms or microbes are ubiquitous or present everywhere. They are even found in harsh
conditions like ice cold or steaming habitats!
• They may occur as a single cell or in colonies.
• Under extreme conditions of temperature and dryness, microorganisms form a hard outer covering
called cyst. They remain inactive inside the cyst.
• They can be beneficial or harmful for us.
4. TYPES OF MICROORGANISMS
Bacteria (singular : bacterium)
Bacteria are microscopic living organisms, usually one-celled, that can be found everywhere. They can be
dangerous, such as when they cause infection, or beneficial, as in the process of fermentation (such as
in wine) and that of decomposition. Bacteria are classified into 4 types on the basis of their shapes.
Coccus(spherical) Bacillus (rod-shaped) Vibrio (comma-shaped) Spirillium (spiral)
5. Algae (singular : alga)
Algae is a simple, non-flowering, and typically aquatic plant of a large assemblage that includes seaweeds and
many single-celled forms. Algae is green in color and also contains chlorophyll but lacks true stems,roots,
leaves, and vascular tissue. Examples are :
Chlamydomonas Fucus Spirogyra
6. Fungi (singular : fungus)
Plant -like organisms that do not contain chlorophyll are called Fungi. Fungi may be unicellular (Yeast) or
multicellular (Bread mould) and are found in warm and moist places. Fungi can be heterotrophic, saprophytic or
parasitic in nutrition. Examples are:
Yeast Rhizopus Penicillium
7. Protozoa (singular : protozoan)
Protozoa are unicellular microscopic organisms similar to animals that can move about to capture food and are
heterotrophic in nature. They are mostly aquatic in nature. They can occur in colonies. Some are parasitic such
as Plasmodium that causes malaria in humans.
Plasmodium Paramecium Euglena
8. Viruses (singular : virus)
Viruses are microscopic organisms that come alive only when inside a host organism (that is they reproduce
only inside another organism) . The host organism could be a bacterium, plant or animal. Common ailments like
cold and influenza (flu) are caused by viruses
COVID-19 BACTERIOPHAGE POLIOVIRUS
9. MICROBES AS OUR FRIENDS
Food and Beverage Industry
• Making breads, dosas, idlis, etc.: Yeast is commonly employed in preparing food items like bread,
cakes, idli, dosa, dhokla, etc.
• Making alcoholic beverages: Yeast is also used in breweries for making wines by the process of
fermentation*. In this process, the yeast ferments the sugar to form alcohol.
*Fermentation- The process in which the microorganisms convert a sugar into an acidor an alcohol.
10. Medicinal Uses
• Making vaccines: Vaccines are made from microbes that are dead or inactive so that
they are unable to cause disease. The antigen in the vaccine is the same as the antigen
on the surface of the disease-causing microbe. The vaccine stimulates the body to
produce antibodies against the antigen in the vaccine. It was the effort of Edward Jenner
that gave the world its first vaccine. The vaccine was against smallpox.
11. • Making antibiotics: Certain bacteria and fungi are used in the production of medicine called
antibiotics that destroy certain disease-causing microbes. Antibiotics are used to control
microbial disease in animals and plants.
• Yeast and bacteria are rich in certain vitamins. Hence they are used in medicines.
Insulin, the hormone used to treat diabetic patients, can also be produced using certain
bacteria.
12. Microbes enhance soil fertility
Bacteria and microbes live, reproduce and die, at enormous rates and in doing so release a
constant stream of nutrients in plant available form. They collect nitrogen and
other nutrients from the soil organic matter and mineral particles. They reproduce, so
more microbes are collecting and converting nutrients.
Bacteriain soil Root nodules where microbes live
13. Microbes help to Maintain a Clean Environment
• The microorganisms decompose dead organic wastes of plants and animals converting
them into simple substances. These substances are again used by other plants and
animals. Thus, microorganisms can be used to degrade the harmful and smelly substances
and thereby cleans up the environment.
• Purifying bacteria, protozoa, and rotifers must either be mixed throughout the water or
have the water circulated past them to be effective. Sewage treatment plants mix these
organisms as activated sludge or circulate water past organisms living on trickling filters
or rotating biological contactors.
15. MICROBES AS FOES
Microbes can be harmful to us in many ways.
• They can cause diseases in humans, plants, and animals.
• They can spoil food.
16. Disease-Causing Microorganisms
• In human beings
Disease Method of spread
Causative
Pathogen
Prevention
Chickenpox Physical contact with the infected person; Air Virus Vaccination
Cholera Contaminated water and food Bacterium Vaccination
Common cold Air Virus Handwashing
Diarrhoea Food or Water-borne Bacterium
Drink filtered water with some salt and
sugar
Malaria Bite of infected mosquitoes Protozoan A check on breeding of mosquitoes
Poliomyelitis(polio) Air, Water Virus Vaccination
Ringworm
From pets or livestock, or from infected
breeding
Fungus
Treated with creams or antibiotics;
Good hygiene
Tuberculosis(TB) Air Bacterium Vaccination
Typhoid Contaminated food Bacterium Proper sanitation practices
17. • In animals
Disease Affected Animal
Causative
Pathogen
Method of Spread
Foot and mouth disease Cattle Virus
Air; Contact with infected
animals
Anthrax Cattle Bacterium Grazing
Finrot Fish Fungus/Bacterium Injury; Dirty Water
Disease Causative Pathogen Method of Spread
Citrus canker
Bacterium
(Xanthomonas)
Air
Yellow Vein Mosaic Virus Insects
Rustof wheat Fungus Air; Seeds
• In plants
18. Someimages of the diseasescaused by microorganisms
Citrus canker Rustof Wheat Yellow Vein Mosaic
Animal sufferingfrom anthrax Finrot Tuberculosis (TB)
19. FOOD SPOILAGE
Food spoilage may be defined as a process or change which makes a product undesirable or
unacceptable for consumption. This complex ecological phenomenon is the outcome of the biochemical
activity of microbial chemical processes which will eventually dominate according to the prevailing
ecological determinants.
20. FOOD PRESERVATION
Foods can be protected from getting spoilt by various techniques of food preservation.
Some of these techniques are discussed below:
Heating- Heat preservation of food generally refers to controlled processes that are performed commercially such as blanching,
pasteurizing, and canning. It is necessary to recognize that there are various degrees of preservation by heating, and that
commercial heat-preserved foods are not truly sterile.
21. Cooling-Coolingis usedtoreducethetemperatureof the foodfrom oneprocessingtemperaturetoanotherortoa requiredstoragetemperature.Chillingis
aprocessingtechniqueinwhichthetemperatureof a foodis reducedandkeptinatemperaturebetween -1to8°C.
Salting -Saltingis amethodof preservingfood,thatwasmorecommonbeforemodernrefrigeration. Saltingpreservesfoodbydrawingwateroutof the food,
preventingbacteriagrowingandspoilingthe food.The foodis surroundedin saltandleftinacool dryplace.
22. Sweetening -Sugaringis a foodpreservation methodsimilartopickling.Sugaringis theprocessof desiccatinga foodbyfirstdehydratingit,thenpackingit
withpuresugar.This sugarcanbecrystallineintheform of tableorrawsugar,oritcanbea highsugardensityliquidsuchas honey,syrupormolasses.
Dehydration - Dehydration is the extraction of moisture from food products like fruits, vegetables, herbs and meat. It inhibits the growth of
microorganismsandimpartsalongstoragelife.
