Higher order taxa:
Bacteria; Proteobactera; Gammaproteobacteria; Chromatiales; Chromatiaceae
Thiocapsa literalis, T. roseopersicina, T. purpurea
Description and Significance
Thiocapsa are sulfur bacteria, meaning that they use reduce sulfur as an electron donor during photosynthesis. They are capable of oxidizing both sulfide and other reduced sulfur compounds. However, the growth of species can be inhbited by excessive amounts of these compounds. The amount of sulfur each organism requires varies from species to species. Thiocapsa are largely anaerobic.
At present there is not yet an extensive body of research on the genome strucutre of Thiocapsa species.
Cell Structure and Metabolism
Thiocapsa are nonmotile Gram-negative bacteria with a purple color. They have a spherical shape. Their photosynthetic equipment consists of two light-harvesting antennae complexes and a reaction center. They contain carotenoids which absorb light in addition to preventing photodamage, the main carotenoid being spirilloxanthin. The major light-harvesting pigment is bacteriochlorophyll a.
Thiocapsa are photosynthetic. Various species require different amounts of light in order to undergo this process, which determines their location in the water column. For example, Thiocapsa roseopersicina prefers high amounts of light, between 1,000 and 2,000 lux. However, Thiocapsa rosea grows at low intensities, usually between 50-300 lux.
Thiocapsa have a typical bacterial life cycle, reproducing by binary fission. They do not form spores.
Thiocapsa are found in aquatic environments, most often in fresh water. These include lakes, sulfur springs, and waste water ponds. The marine habitats include: shoreline sediments, lagoons, fjords, salt and soda lakes, sea ice, and the Black Sea. Their habitats have little or no oxygen. Under ideal conditions, Thiocapsa can form dense blooms.
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