Vaccines comprise dead, inactivated or weakened microorganisms. This preparation can either be injected or administered orally, depending on the type of vaccine. It helps develop immunity against the pathogen administered. Examples of vaccines are measles, mumps, and rubella (MMR) vaccine and the varicella (chickenpox) vaccine.

All algal, fungal and bacterial cells possess cell walls. The algal cell wall is mainly composed of cellulose, fungal cell wall comprise chitin and bacterial cell wall is mainly made up of peptidoglycan.

Protozoa are single-celled eukaryotes that commonly show characteristics usually associated with animals, most notably mobility and heterotrophy. Like animal cells, protozoans also lack a cell wall.

Jonas Salk developed the first effective poliomyelitis (polio) vaccine which consisted of inactivated poliovirus.

Fermentation is a process by which carbohydrates are changed into alcohols and carbon dioxide by bacteria or yeast under anaerobic conditions.

Fermentation also involves the conversion of milk sugar (lactose) by Lactobacillus to produce lactic acid. These bacteria denature milk protein (casein) so that they clump together to form curd.

Rhizobium is a nitrogen fixing bacterium, usually found in the root nodules of leguminous plants. This bacterium and leguminous plants are in a symbiotic relationship with each other. The nitrogen fixed by the bacteria is utilised by the plant and in turn Rhizobium receives nourishment and shelter from the plant.

• Antibiotics are chemicals extracted from microorganisms to kill some other microorganisms. These chemicals are used to kill or stop the growth of the disease-causing bacteria.


• Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.


• Some antibiotics prevent the synthesis of the cell walls of certain bacteria and so kill them. Just like any other medicine, some people are allergic to certain antibiotics.

Fermentation is the natural process in which sugars are converted to alcohol by yeast. Carbon dioxide is also released in this reaction as a byproduct. This process is used in distilleries (alcohol industries) for the production of wine, beer and spirits.