NUMERICAL TAXONOMY OF HETEROTROPHIC SULFUR-OXIDIZING BACTERIA ISOLATED FROM SOUTHWESTERN PACIFIC HYDROTHERMAL VENTS

Sulfur-oxidizing bacteria (n = 161) were enriched and isolated from sa mples of vent water, invertebrates, and chimney rocks collected at two deep-sea hydrothermal vents (2000 m) in back-are basins from the sout hwestern Pacific: the North Fiji Basin and the Lau Basin, Several type s of heterotrophic sulfur-oxidizing bacteria were repeatedly isolated. They oxidized thiosulfate either to sulfate (acid producing) or to po lythionate (base producing). In most of the acid-producing cultures, t hiosulfate was transitorily oxidized to polythionate. All of the bacte ria were Gram negative, 37% were fermentative, and 88% were denitrifie rs or nitrate reducers. Numerical taxonomy and analysis of the G+C con tent showed that they belong to several genera including Pseudomonas, Acinetobacter, and Vibrio.