Green sulfur bacteria
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). The phylum is most closely related to Bacteroidetes.
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.
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