Title: Isotope effects associated with the anaerobic oxidation of sulfide by the purple photosynthetic bacterium,<i>Chromatium vinosum</i>
Abstract: Small inverse isotope effects of 1–3‰ were consistently observed for the oxidation of sulfide to elemental sulfur during anaerobic photometabolism by Chromatium vinosum. The inverse fractionation can be accounted for by an equilibrium isotope effect between H2S and HS−, and may indicate that C. vinosum (and other photosynthetic bacteria) utilizes H2S rather than HS− as the substrate during sulfide oxidation.