Temperature effect on the sulfur isotope fractionation during sulfate reduction by two strains of the hyperthermophilic Archaeoglobus fulgidus

• DOI: 10.1111/j.1462-2920.2009.02002.x
• Publication Date: 2009-07-17T17:08:05Z
• Authors: Kristen Mitchell; Anne Heyer; Donald E. Canfield; Joost Hoek; Kirsten S. Habicht
• Keywords: 0301 basic medicine; 03 medical and health sciences; Sulfates; Archaeoglobus fulgidus; Sulfur Isotopes; Temperature; Extreme Heat; Chemical Fractionation

SummarySulfur isotope fractionation during dissimilatory sulfate reduction by two strains of the thermophilic archaeon Archaeoglobus fulgidus (strains VC‐16 and Z) was explored over the entire temperature range of growth. The optimal cell‐specific sulfate reduction rate (14 fmol cell−1 h−1) was found at 82–84°C but growth was measured as low as 54°C. The fractionation ranged between 0.52‰ and 27‰, with largest fractionations were found at intermediate temperatures and the smallest fractionations at the lowest and highest temperatures. There was an inverse relationship between the cell‐specific sulfate reduction rate and fractionation, and the cell‐specific rate was a good indicator of the expected fractionations regardless of whether temperature or substrate concentrations controlled the rate. Comparison of the fractionation trend found in this study with similar measurements for seven other sulfate‐reducers showed that sulfate‐reducing organisms respond to temperature in three different ways and this correlated with their maximum fractionation value, but not with the cell‐specific sulfate reduction rate. A sulfur isotope model was used to reproduce the observed variation of fractionation with temperature. This approach predicted the rate of internal sulfur transformations as having the major influence on the observed fractionations in the intermediate temperature range, whereas the exchange of sulfate across the cell membrane controls fractionation at low and high temperatures.