© 2003 Heron Publishing—Victoria, Canada
Minimal sulfur requirement for growth and sulfur-dependent metabolism of the hyperthermophilic archaeon Staphylothermus marinus
Xiaolei Hao (1) and Kesen Ma (1, 2)
1. Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada / 2. Author to whom correspondence should be addressed ([email protected]) / Received April 14, 2003; accepted August 13, 2003; published online September 19, 2003
Staphylothermus marinus is an anaerobic hyperthermophilic archaeon that uses peptides as carbon and energy sources. Elemental sulfur (Sº) is obligately required for its growth and is reduced to H2S. The metabolic functions and mechanisms of Sº reduction were explored by examining Sº-dependent growth and activities of key enzymes present in this organism. All three forms of Sº tested—sublimed Sº, colloidal Sº and polysulfide—were used by S. marinus, and no other sulfur-containing compounds could replace Sº. Elemental sulfur did not serve as physical support but appeared to function as an electron acceptor. The minimal Sº concentration required for optimal growth was 0.05% (w/v). At this concentration, there appeared to be a metabolic transition from H2 production to Sº reduction. Some enzymatic activities related to Sº-dependent metabolism, including sulfur reductase, hydrogenase, glutamate dehydrogenase and electron transfer activities, were detected in cell-free extracts of S. marinus. These results indicate that Sº plays an essential role in the heterotrophic metabolism of S. marinus. Reducing equivalents generated by the oxidation of amino acids from peptidolysis may be transferred to sulfur reductase and hydrogenase, which then catalyze the production of H2S and H2, respectively.
Keywords: electron transfer activity, glutamate dehydrogenase, hydrogen, hydrogenase, hyperthermophile, sulfide, sulfur reductase.
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