Quadruple sulfur isotope fractionation during microbial sulfur disproportionation in Caldimicrobium thiodismutans

Abstract

Stable sulfur isotope ratios are useful not only for understanding microbial activity in the modern and past sulfur cycle, but also for making habitat inferences based on the isotopic fractionation of sulfur from its microbial metabolism. Along with sulfur reduction, sulfur disproportionation is an important sulfur metabolism that increases the sulfur isotopic fractionation between sulfate and sulfide in the sedimentary record. A quadruple sulfur isotopic signature has been proposed to distinguish between sulfur reduction and sulfur disproportionation, but its usefulness as an indicator has not yet been evaluated due to the paucity of research results. In this study, we analyzed quadruple sulfur isotopic fractionations of thermophilic sulfur disproportionation bacteria isolated from the Nakabusa hot spring, and compared it with the previous study in which the bacteria were cultured at low temperatures to discuss the characteristics of the sulfur disproportionation bacteria and the effectiveness of the indicator under high temperature conditions.