The green sulfur bacteria are a family (Chlorobiaceae) of phototrophic[?] bacteria. No other bacterial families are known to be closely related to them, and they are accordingly placed in their own phylum (Chlorobi).
Green sulfur bacteria are generally nonmotile (one species has a flagellum), and come in spheres, rods, and spirals. Their environment must be oxygen-free, although they need light to grow. They engage in photosynthesis, using bacteriochlorophylls[?] c, d, and e in vesicles attached to the membrane, and in the presence of sulfur, which acts as electron donor. This is used in the form of sulfide[?] ions, producing globules of neutral sulfur outside the cell, which may then be further oxidized.
