Cyanobacteria, one of the photosynthetic bacteria, consist of chlorophyll, whereas the other forms of photosynthetic bacteria consist of bacteriochlorophyll. Although bacteriochlorophyll is similar to chlorophyll, it absorbs light of a broad wavelength than chlorophyll. In addition, because bacteria that contain bacteriochlorophyll do not use water as the electron donor, they do not produce oxygen. Bacteria such as purple and green sulfur bacteria use sulfur as the electron acceptor. Purple nonsulfur bacteria constitute a nontaxonomic group of versatile organisms, in which most of them can grow as photoheterotrophs, photoautotrophs, or chemoheterotrophs – switching from one mode to another depending on conditions such as: degree of anaerobiosis and availability of carbon source (CO2 for autotrophic growth, organic compounds for heterotrophic growth) and light (needed for phototrophic growth). These bacteria do not use hydrogen sulfide as an electron donor when growth occurs photoautotrophically. Because H2S is toxic at higher concentrations, this bacteria can use H2 and low concentration of sulfide such as S-, S2O3-, and …show more content…
The Calvin cycle enzymes are located in two separated operons. The cbbI operon comprises the structural genes that encode Calvin cycle enzymes: fructose 1,6-bisphosphatase (cbbF1, ~37kDa), phosphoribulokinase (prkA, ~40kDa), fructose-bisphosphate aldolase (cfxA, ~31kDa), Form I ribulose bisphosphate carboxylase/oxygenase (Rubisco) large subunit (cbbL, ~54kDa), and Form I ribulose bisphosphate carboxylase/oxygenase (Rubisco) small subunit (cbbS, ~14kDa) (L8S8). The cbbII operon consists of the structural genes that encode Calvin cycle enzymes: fructose 1,6-bisphosphatase (fbpB, ~37kDa), phosphoribulokinase (prkB, ~32kDa), transketolase (tklB, ~72kDa), glyceraldehyde-3-phosphate dehydrogenase (gapB, ~37kDa), fructose bisphosphate aldolase (cfxB, ~39kDa), and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) large subunit (rbpL, ~51kDa)