RESUMEN
Sulfur isotope ((34)S/(32)S) fractionation during reduction of dissolved sulfate was investigated with a growing batch culture of a thermophilic, gram-negative, sulfate-reducing bacterium (strain MT-96) at 60 degrees C. The completely oxidizing strain was isolated from geothermally heated sediments of a shallow-water hydrothermal vent in the Mediterranean Sea. The hydrogen sulfide produced in the experiments was enriched in (32)S by approximately 19 per thousand as compared to sulfate, which indicates that stable isotope discrimination by this thermophile is within the range found previously for mesophilic sulfate-reducing bacteria, and only slightly higher than that observed for the thermophilic gram-positive Desulfotomaculum nigrificans.
RESUMEN
Sulfur isotope fractionation during reduction of thiosulfate was investigated with growing batch cultures of Desulfovibrio desulfuricans CSN (DSM 9104) at 30 degreesC. The sulfide produced was depleted in 34S by 10 per thousand as compared to total thiosulfate sulfur. The depletion was equal to that during sulfate reduction under similar conditions. The two sulfur atoms of the thiosulfate molecule were affected differently by fractionation. Sulfide produced from sulfonate sulfur was depleted by 15.4 per thousand, sulfide produced from sulfane sulfur by 5.0 per thousand.