Purple sulfur bacteria Purple sulfur bacteria The purple sulfur bacteria (PSB) are part of a group of Proteobacteria 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. Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen. Instead, they can use sulfur in the form of sulfide, or thiosulfate (as well, some species can use H, Fe, or NO) as the electron donor in
Carotenoid Carotenoid Carotenoids (), also called tetraterpenoids, are organic pigments that are produced by plants and algae, as well as several bacteria and fungi. Carotenoids give the characteristic color to carrots, corn, canaries, and daffodils, as well as egg yolks, rutabagas, buttercups, and bananas. Carotenoids can be produced from fats and other basic organic metabolic building blocks by all these organisms. The only animals known to produce carotenoids are aphids and spider mites, which acquired the ability and genes from fungi or it is produced by endosymbiotic bacteria in whiteflies. Carotenoids from the diet are stored in the fatty tissues of