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Chloroplasts have many similarities with photosynthetic bacteria, including a circular chromosome, prokaryotic-type ribosome, and similar proteins in the photosynthetic reaction center. [68] [69] The endosymbiotic theory suggests that photosynthetic bacteria were acquired (by endocytosis) by early eukaryotic cells to form the first plant cells ...
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.
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.
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.
Regarding their photosynthetic pigment composition, in the Chromatiaceae can be found bacteriochlorophyll a or b and different types of carotenoids, according to the species. They confer to these bacteria their characteristic pigmentation, and if the amount of cells in the medium is high enough, the coloring may also be visible to the naked eye.
Some bacteria have cell wall structures that are neither classically Gram-positive or Gram-negative. This includes clinically important bacteria such as mycobacteria which have a thick peptidoglycan cell wall like a Gram-positive bacterium, but also a second outer layer of lipids. [78]
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]
The photosynthetic pigments present in their chloroplasts make diatoms greenish-brown. The stramenopiles, also known as heterokontophytes, are a very large and diverse group of eukaryotes. It inlcludes Ochrophyta—which includes diatoms, brown algae (seaweeds), and golden algae (chrysophytes) [39] — and Xanthophyceae (also called yellow ...