BACTERIAL PHOTOSYNTHESIS

BACTERIAL PHOTOSYNTHESIS

Like green plants, some purple and green sulphur bacteria are capable of synthesizing their organic food in Presence of light and in absence of O2 , which is known as bacterial photosynthesis

General equation of bacterial photosynthesis has been given by Van Neil (1950):

CO2 + 2H2A -------Bacteriochlorophyll or Chlorobium chlorophyll ------> (CH2O)+ 2A + 2H2O

Some important examples of photosynthesis bacteria are :

i.)                  Green sulphur bacteria :- e.g , Chlorobium .it contains chlorobium chlorophyll , which absorb 720-750 nm (Far red light) of wavelength of light

ii.)                 Purple sulphur bacteria : e.g, Chromatium

iii.)               Non-sulphur bacteria :- e.g , Rhodospirillum

Purple sulphur bacteria and non-sulphur bacteria contain bacterichlorophyll , which is having 2H-atoms more than chl-a and it absorbs 850-950nm (infrared) wavelength of light, which is poor in energy and hence unable to use and split H2O and thus no O2 evolution in bacterial photosynthesis

Characteristics are ;-

a.       No definite cholorplast but contain simple structures having pigments called chromatophores

b.      Contain chlorobium chlorophyll or bacterialchlorophyll  

c.       Use longer wavelengths of light (750-950nm)

d.      No utilization of H2O

e.      No Evolution of O2

f.        Photoreductant is NADH2

g.       Only One photoact and hence one pigment system and thus one reaction centre i.e, p890

h.      Cyclic photophosphorylation iss dominant

i.         It Occurs in presence of light and in absence of O2

Chemosynthesis :-

Some aerobic bacteria are capable of manufacturing their organic food, utilizing chemical energy released in oxidation of some inorganic substances (not light energy) . This phenomenon of formation of organic food utilizing chemical energy is called chemosynthesis

Examples :-

1.       Nitrifying bacteria :- e.g, Nitrosomonas, Nitrosococcus & Nitrobacter etc.

2.       Sulphur bacteria :- e.g., Beggiatoa, Thiothrix & Thiobacillus

They oxidize H2S ---[O]----> S + H2O + Chemical energy

3.       Iron Bacteria :- e.g., Ferrobacillus , Leptothrix & Calothrix

They oxidize  Fe2(+) ------> Fe3(+ ) + Energy

4.       Hydrogen bacteria :- e.g., Bacillus pentotrophus

H2 -----[O]------>  H2O + Chemical Energy

5.       Carbon Bacteria :- e.g., Bacillus oligocarbophilus

CO ---[O]---->CO2 + Chemical Energy