Chlorobium

Chlorobium is a genus of green sulfur bacteria. They are photolithotrophic oxidizers of sulfur and most notably utilise a noncyclic electron transport chain to reduce NAD+. Hydrogen sulfide is used as an electron source and carbon dioxide its carbon source.

Chlorobium species exhibit a dark green color; in a Winogradsky column, the green layer often observed is composed of Chlorobium. This genus lives in strictly anaerobic conditions below the surface of a body of water, commonly the anaerobic zone of a eutrophic lake.

The complete C. tepidum genome, which consists of 2.15 megabases (Mb), has recently been published. It synthesizes chlorophyll a and bacteriochlorophylls (BChls) a and c, of which the model organism has been used to ellucidate the biosynthesis of BChl c. Several of its carotenoid metabolic pathways (including a novel lycopene cyclase) have similar counterparts in cyanobacteria.