Novel vacuolate sulfur bacteria from the Gulf of Mexico reproduce by reductive division in three dimensions.

Large spherical sulfur bacteria, 180-375 microm in diameter, were found regularly and in abundance in surface sediments collected from hydrocarbon seeps (water depth 525-640 m) in the Gulf of Mexico. These bacteria were characterized by a thin 'shell' of sulfur globule-filled cytoplasm that surrounded a central vacuole (roughly 80% of biovolume) containing high concentrations of nitrate (average 460 mM). Approximately 800 base pairs of 16S rRNA gene sequence data, linked to this bacterium by fluorescent in situ hybridization, showed 99% identity with Thiomargarita namibiensis, previously described only from sediments collected off the coast of Namibia (Western Africa).