The green sulfur bacteria (Chlorobiaceae) are a family of obligately anaerobic photoautotrophic bacteria. Together with the non-photosynthetic Ignavibacteriaceae, they form the phylum Chlorobi. Most closely related to the distant Bacteroidetes, they are accordingly assigned their own phylum.[1]
Green sulfur bacteria are nonmotile (except Chloroherpeton thalassium, which may glide).[1] Photosynthesis is achieved using a Type 1 Reaction Centre using bacteriochlorophyll (BChl) a and in chlorosomes which employ BChl c, d, or e; in addition chlorophyll a is also present.[2][1] They use sulfide ions, hydrogen or ferrous iron as an electron donor and the process is mediated by the type I reaction centre and Fenna-Matthews-Olson complex. Elemental sulfur deposited outside the cell may be further oxidized. By contrast, the photosynthesis in plants uses water as the electron donor and produces oxygen.[1]