<P> Like plants, the cyanobacteria use water as an electron donor for photosynthesis and therefore liberate oxygen; they also use chlorophyll as a pigment . In addition, most cyanobacteria use phycobiliproteins, water - soluble pigments which occur in the cytoplasm of the chloroplast, to capture light energy and pass it on to the chlorophylls . (Some cyanobacteria, the prochlorophytes, use chlorophyll b instead of phycobilin .) It is thought that the chloroplasts in plants and algae all evolved from cyanobacteria . </P> <P> Several other groups of bacteria use the bacteriochlorophyll pigments (similar to the chlorophylls) for photosynthesis . Unlike the cyanobacteria, these bacteria do not produce oxygen; they typically use hydrogen sulfide rather than water as the electron donor . </P> <P> Recently, a very different pigment has been found in some marine γ - proteobacteria: proteorhodopsin . It is similar to and probably originated from bacteriorhodopsin (see below under archaea). Bacterial chlorophyll b has been isolated from Rhodopseudomonas spp . but its structure is not yet known </P> <P> Green algae, red algae and glaucophytes all use chlorophylls . Red algae and glaucophytes also use phycobiliproteins, but green algae do not . </P>

Where are the photosynthetic pigments located in prokaryotes