Autotrophic Nutrition

Organisms which prepare their own food are said to have autotrophic mode of nutrition.

Phototrophs

Most of the members of kingdom plantae, protists like Diatoms, prokaryotes like Cyanobacteria, few bacteria use solar energy to synthesize the food for example:

1. purple sulphur bacteria - Chromatium
2. green sulphur bacteria - Chlorobium

The process is physico-chemical. These are photosynthetic autotrophs or photoautotrophs. They have photosynthetic pigments.

Chemoautotrophs

There are some chemoautotrophs, which prepare their food by chemosynthesis, i.e. they use energy released during chemical reactions for synthesis of food.

The examples of chemosynthetic autotrophs are bacteria such as,

1. Nitrifying bacteria (Nitrosomonas),
2. Sulphur bacteria (Thiobacillus),
3. Iron bacteria {Ferrobacillus).