Survival of sulfate-reducing bacteria after oxygen stress, and growth in sulfate-free oxygen-sulfide gradients |
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Authors: | Heribert Cypionka Friedrich Widdel Norbert Pfennig |
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Institution: | Fakultät für Biologie, Universität Konstanz, Postfach 5560, D-7750 Konstanz, F.R.G. |
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Abstract: | Abstract The survival after oxygen stress was studied with eight species of sulfate-reducing bacteria. In the absence of sulfide all species tolerated 6 min of aeration without loss of viability. Even after 3 h of aeration the viability of four species ( Desulfovibrio vulgaris, D. desulfuricans, D. salexigens and Desulfobacter postgatei ) was not impaired. Four other species were sensitive to 3 h of aeration: the surviving fractions of Desulfotomaculum ruminis, D. nigrificans and Desulfococcus multivorans were about 1%, that of Desulfotomaculum orientis about 0.01%. Formation of spores resulted in oxygen resistance of D. orientis . Reducing agents did not protect the vegetative cells of this strain against oxygen toxicity. In contrast, sulfhydryl group-containing agents increased the oxygen sensitivity considerably. Growth of sulfate- and sulfur-reducing bacteria in oxygen-sulfide gradients in agar tubes was studied. In the gradients these strictly anaerobic bacteria revealed oxygen-dependent growth in sulfate- and sulfur-free medium. Three sulfate-reducing bacteria that could not use thiosulfate or sulfur as electron acceptor failed to grow in oxygen-sulfide gradients. Obviously, not directly molecular oxygen, but oxidation products of sulfide, such as thiosulfate or sulfur, were used as electron acceptors and were continuously regenerated in a cycling process from sulfide by autoxidation. The conceivable ecological significance of a short sulfur cycle driven by autoxidation of sulfide is discussed. |
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Keywords: | Oxygen toxicity to anaerobes sulfate reduction sulfur reduction thiosulfate reduction sulfide oxidation sulfur cycle |
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