NUTRITION OF BACTERIA

                The bacterial cell has the same general chemical pattern of the cells of other organisms. The principal constituent of bacterial cell is water which represents about 80% of the total weight. Proteins, polysaccharides, lipids, nucleic acids, mucopeptides and low molecular weight compounds make up the rest.

            For the growth and multiplication of bacteria, the minimum nutritional requirements are water, a source of carbon, a source of nitrogen and some inorganic salts. Depending upon the mode of nutrition, bacteria are recognized into two groups – Autotrophic and heterotrophic bacteria.

            1. AUTOTROPHIC BACTERIA:- Some of the bacteria have the capacity to synthesize organic food materials by themselves from the organic and inorganic substances. On the basis of energy source and the nature of substances autotrophs are divided into two groups –

            Phototrophs:- This group of bacteria can synthesize the radiant energy into chemical energy like the higher plants. Example – Purple sulphur bacteria, green sulphur bacteria, cyanobacteria, etc.

            Chemotrophs:- This group of bacteria are non-photosynthetic but autotrophic and derive energy from ammonia, nitrate, nitrite, iron, hydrogen sulphide and other inorganic compounds. Example – Sulphur bacteria, hydrogen bacteria, iron bacteria, nitrifying bacteria, etc.

            2. HETEROTROPHIC BACTERIA:- Majority of the bacteria are unable to synthesize their food material due to the absence of pigments. These bacteria obtain readymade food from any organic source. Heterotrophs may be divided into three nutritional groups –

            Parasitic Bacteria:- They feed on living organisms (host) and mant of them cause diseases which are known as pathogenic bacteria. Many diseases of plants and animals including human beings are caused by pathogenic bacteria. Example – Cabbage rot, pear blight, citrus canker, etc., are some bacterial diseases of plants.

            Saprophytic Bacteria:- They grow on dead and decaying organic matter and they btain food materials by decomposing the complex organic matters by the process of fermentation and putrefaction. Example – Lacto bacillus bacteria, which converts milk into curd by fermentation.

            Symbiotic Bacteria:- They grow in close association with other living organisms without harming each other. Example – Root nodule bacteria (Rhizobium), live in the roots of leguminous plants which supply nitrogen to the plant by fixing atmospheric nitrogen and in return the plant provide s them shelter and carbohydrates.

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