8th Class Science Microorganisms : Friend and Foe Useful Microorganisms

       Useful Microorganisms

At first it was believed that microorganisms are all harmful and cause diseases. But later on it was found to be not true. There are many microorganisms, which are useful to us, serving many purposes of human beings. They are utilized in making curds, bread and cake. They are also used for producing alcohol, wine and acetic acid. They can also be used for the preparation of medicines called antibiotics. Some of the microorganisms help to fix atmospheric nitrogen to improve the nitrogen content of the soil. They can recycle the organic matters from the nature. Some of the common antibiotics, which are made from the fungi and bacteria are penicillin, streptomycin and tetracycline. The first antibiotic is penicillin.

            Cleaning of Environment

There are some microorganisms, which decompose the organic wastes and reduce the complex matter into the simpler form. These matters get added up into the soil and increas its nutrient content, helping in the growth of new plant. In addition, they also help in recycling of nutrients present in the nature, which can be used as food by the green plants.

           Commercial Uses of Microorganisms

Microorganisms are used for the large scale production of alcohol and acetic acid. Yeast is used for production of alcohol, in making of wine, beer and whisky. It is also used for production of industrial.spirit. Yeast can convert sugar into alcohol by a process called fermentation, which was discovered by Louis Pasture in 1857. Bacteria can also convert alcohol into acetic acid. The acetobacter can convert alcohol into acid.

         We know that all the microorganisms are not harmful. Some are useful, without which, the life would not have been possible on the earth. The microorganisms, which help to convert atmospheric nitrogen into nitrate and increase the nitrogen content of the soil is:

(a) Bacillus

(b) Rhizobium bacteria

(c) Lactobacillus

(d) Fungus

(e) None of these

Answer: (b)

Explanation

The only bacteria, which converts atmospheric nitrogen into nitrate and increase the nitrogen content of the soil is Rhizobium bacteria.

       There are some microorganisms, which decomposes the waste products and remains of dead plant and animals. This helps in keeping the environment clean. They are known as:

(a) Parasitic

(b) Consumer

(c) Decomposer

(d) Producer

(e) None of these

Answer: (c)

Explanation

The microorganisms, which are friend to us and help us in cleaning our environment are known as decomposers.