Nutrition in Plant Bacteria

Nutrition in Bacteria

Autotrophic 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.

Photoautotrophic bacteria

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

1. Photolithotrops

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.

2. Photo-organolithotrophs

In this the hydrogen donor is an organic acid or alcohol eg. Purple non sulphur bacteria (eg. Rhodospirillum)

Chemoautotrphic bacteria

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

1. Chemolithotrophs: Inorganic compound is oxidized to release energy. eg. Sulphur bacteria (eg. Thiobacillus) Iron   bacteria   (eg.   Ferrobacillus),   Hydrogen   bacteria   eg. Hyderogenomonas and Nitrifying bacteria (eg Nitrosomonas and Nitrobacter)

2. Chemo - organotrophs : In this type it is an organic compound that is oxidized to release energy. eg. Methane bacteria (Methanococcus). Acetobacteria and Lactobacillus are also examples for chemo-organotrophs.

Heterotrophic Bacteria

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).