Photosynthetic bacteria evolution

Maruthamuthu, R, Muthu, S., Gurunathan, K.,Ashokkumar, M., Sastri, M.V.C. 1992. Rhotobioca-talysis hydrogen evolution using a semiconductor coupled with photosynthetic bacteria. Int J Hydrogen Energy 17 863-866. 

Modern bacteria inhabit almost every ecological niche in the biosphere, and there are bacteria capable of using virtually every type of organic compound as a source of carbon and energy. Photosynthetic bacteria in both fresh and marine waters trap solar energy and use it to generate carbohydrates and all other cell constituents, which are in turn used as food by other forms of life. The process of evolution continues—and in rapidly reproducing bacterial cells, on a time scale that allows us to witness it in the laboratory. 

It is interesting to note that bacterial photosynthesis may not necessarily result in a net CO2 uptake a net CO2 evolution may occur in some circumstances. Species of purple photosynthetic bacteria, for example, can use organic compounds instead of CO2, as the major carbon source for cell synthesis. When the exogenic carbon source is less oxidized them cell material oxidation of the exogenic carbon to the level of cell material is coupled to reduction and assimilation of COj. However if the carbon source is more oxidized than cell materieil, part of the substrate is necessarily oxidized anaerobically to CO2. 

Substrate concentrations were adjusted stoichiometrically to yield 300 mmol H2 per liter of culture by photosynthetic bacteria. Actively growing cultures of BC 1 or strain A-501 were inoculated into each medium to obtain a final OD eo of 0.6. The samples were incubated at 30 C under tungsten lamp illumination (330 W/m2) until H2 evolution ceased (approx. 100... 

It has been suggested that all the gram positive bacteria may have descended from photosynthetic ancestors and indeed that the ancestor of all eubacteria was photosynthetic (5). It is, therefore, important to search for other new types of photosynthetic bacteria in an effort to shed more light on the early evolution of photosynthesis. Our findings suggest that such organisms may not be ubiquitous and will require specific enrichment methods for their isolation. REFERENCES... 

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