Purple bacteria

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. They may be divided into two groups – purple sulfur bacteria (Chromatiales, in part) and purple non-sulfur bacteria. Purple bacteria are anoxygenic phototrophs widely spread in nature, but especially in aquatic environments, where there are anoxic conditions that favor the synthesis of their pigments.^[2]