Nutrition in Bacteria
Some bacteria can synthesize their food and hence they are autotrophic in their mode of nutrition. They may be photo autotrophs(eg. Spirillum) or chemoautotrophs eg. Nitrosomonas or Nitrobacter.
They use sunlight as their source of energy to synthesize food. But unlike photosynthetic eukaryotic cells they do not split water to obtain reducing power. So Oxygen is not evolved during bacterial photosynthesis. Depending upon the nature of the hydrogen donor these bacteria may be
In this the hydrogen donor is an inorganic substance. In green sulphur bacteria(eg. Chlorobium) hydrogen sulphide (H2s) is the hydrogen donor. The chlorophyll is bacterioviridin
In purple sulphur bacteria (eg. Chromatium) thiosulphate acts as hydrogen donor. The chlorophyll is bacteriochlorophyll.
In this the hydrogen donor is an organic acid or alcohol eg. Purple non sulphur bacteria (eg. Rhodospirillum)
They do no have photosynthetic pigments and hence they cannot use sunlight energy. Instead they obtain energy in the form of ATP by oxidising inorganic or organic compounds. The energy thus obtained is used to reduce CO2 to organic matter. Based on the type of substance oxidized they may be
They depend upon other organisms (living/dead) for their food since they cannot synthesize their own food. They may be saprotrophic e.g (Bacillus subtilis), parasitic e.g. Plant parasite-(Xanthomonas citrii) animal parasite e.g.(Bacillus anthracis) , Human parasite e.g (Vibrio cholerae) or symbiotic in association with roots of the family Leguminosae. e.g. (Rhizobium).