Search results
Results from the WOW.Com Content Network
Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. [1] They are pigmented with bacteriochlorophyll a or b , together with various carotenoids , which give them colours ranging between purple, red, brown, and orange.
Cyanobacteria is the only prokaryotic group that performs oxygenic photosynthesis. Anoxygenic photosynthetic bacteria use PSI- and PSII-like photosystems, which are pigment protein complexes for capturing light. [5] Both of these photosystems use bacteriochlorophyll. There are multiple hypotheses for how oxygenic photosynthesis evolved.
Other photosynthetic bacterioplankton, including purple and green bacteria, undergo anoxygenic photosynthesis in anaerobic conditions. The pigments synthesized in these organisms are sensitive to oxygen. In purple bacteria the major pigments include bacteriochlorophyll a and b and carotenoids.
The photosynthetic cyanobacteria are arguably the most successful bacteria, and changed the early atmosphere of the earth by oxygenating it. [15] Stromatolites , structures made up of layers of calcium carbonate and trapped sediment left over from cyanobacteria and associated community bacteria, left behind extensive fossil records.
Following present classification, there are a little less than 9,300 known species of prokaryotes, which includes bacteria and archaea; [185] but attempts to estimate the true number of bacterial diversity have ranged from 10 7 to 10 9 total species—and even these diverse estimates may be off by many orders of magnitude.
The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic , and are often found in stratified water environments including hot springs , stagnant water bodies, as well as microbial mats in intertidal zones.
Oxygenic photosynthesis can be performed by plants and cyanobacteria; cyanobacteria are believed to be the progenitors of the photosystem-containing chloroplasts of eukaryotes. Photosynthetic bacteria that cannot produce oxygen have only one photosystem, which is similar to either PSI or PSII.
In general, photosynthesis in cyanobacteria uses water as an electron donor and produces oxygen as a byproduct, though some may also use hydrogen sulfide [79] a process which occurs among other photosynthetic bacteria such as the purple sulfur bacteria. Carbon dioxide is reduced to form carbohydrates via the Calvin cycle. [80]