The packet which was put in the refrigerator did not have a bad smell because there was a cold temperature and bacteria cannot grow there. Decomposition by bacteria in the packet left on the table caused a bad smell.

The relationship between two organisms in which both the organisms are benefitted is called symbiotic relationship.

Rhizobium bacteria live in the root nodules of leguminous plants.

Alexander Fleming discovered first antibiotic penicillin. Two other common antibiotics are streptomycin and tetracycline.

To prevent ourselves from cholera we should maintain personal hygiene and good sanitary habits.

Some micro-organisms decompose the organic waste and dead plants and animals into simple substance and clean up the environment.

Curd contains several microorganisms. Of these, the bacterium, Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd.

Anabaena and Nostoc are two blue-green algae which help in nitrogen fixation.

Curd is added to idlis and bhatura to make them soft.

Vaccine is essential to protect all children against several diseases. Polio and hepatitis are two diseases for which vaccines are available.

The disease causing microorganisms are called pathogens.

We should avoid collection of water anywhere because this water serves as breeding ground for mosquitoes.

Bacillus anthracis causes of anthrax.

Fermentation is the process by which yeast converts sugars into alcohol.

Baking bread/manufacturing of alcoholic drinks is the commercial use of yeast.