Based on nutrition bacteria are classified into following types.
(1) Autotrophic bacteria : They synthesize their own food. They are further classified into two types ;
(A) Photoautotrophic bacteria :
They are autotrophs and synthesize their food by absorbing light energy. They contain bacteriochlorophyll and bacteriocidin to absorb light energy.
Example: Green sulphur bacteria like chlorobium, purple sulphur bacteria like chromatium. These bacteria use H2S as their source of hydrogen, so O2 is not liberated.
(B) Chemoautotrophic bacteria:
They are autotrophs, utilizes (utilises) chemical energy for the food synthesis. They get chemical energy by the oxidation of chemical substances of nature. Example: Nitrifying bacteria, sulphur bacteria etc.
(2) Hetero trophic bacteria: They do not synthesize their own food but obtain food by two methods.
- Saprophytic method.
- Parasitic method.
The bacteria obtain their food by feeding on **** organic matter are called saprophytic bacteria. The bacteria obtain their food by living inside or outside the body of other organisms are called parasitic bacteria.
