THIOSULFATE REDUCTION, AN IMPORTANT PHYSIOLOGICAL FEATURE SHARED BY MEMBERS OF THE ORDER THERMOTOGALES

Several members of the order Thermotogales in the domain Bacteria, viz ., Thermotoga neapolitana, Thermotoga maritima, Thermosipho africanus, Fervidobacterium islandicum, and Thermotoga strain SEER 2665, an isol ate from an oil well, reduced thiosulfate to sulfide. This reductive p rocess enhanced cellular yields and growth rates of all the members bu t was more significant with the two hyperthermophiles T. neapolitana a nd T. maritima. This is the first report of such an occurrence in this group of thermophilic and hyperthermophilic anaerobic bacteria. The r esults suggest that thiosulfate reduction is important in the geochemi cal cycling of sulfur in anaerobic thermal environments such as the sl ightly acidic and neutral-pH volcanic hot springs and oil reservoirs.