Anaerobic Elemental Sulfur Reduction by Fungus Fusarium oxysporum

Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan.
Bioscience Biotechnology and Biochemistry (Impact Factor: 1.06). 11/2007; 71(10):2402-7. DOI: 10.1271/bbb.70083
Source: PubMed


Reduction of inorganic sulfur compounds by the fungus Fusarium oxysporum was examined. When transferred from a normoxic to an anoxic environment, F. oxysporum reduced elemental sulfur to hydrogen sulfide (H2S). This reaction accompanied fungal growth and oxidation of the carbon source (ethanol) to acetate. Over 2-fold more of H2S than of acetate was produced, which is the theoretical correlation for the oxidation of ethanol to acetate. NADH-dependent sulfur reductase (SR) activity was detected in cell-free extracts of the H2S-producing fungus, and was found to be up-regulated under the anaerobic conditions. On the other hands both O2 consumption by the cells and cytochrome c oxidase activity by the crude mitochondrial fractions decreased. These results indicate that H2S production involving SR was due to a novel dissimilation mechanism of F. oxysporum, and that the fungus adapts to anaerobic conditions by replacing the energy-producing mechanism of O2 respiration with sulfur reduction.

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    • "Analytical measurements of metabolism have revealed anoxic NH 3 fermentation is widely conserved amongst other soil-dwelling fungi (Zhou et al. 2002), but it is not clear whether most of these species can use NH 3 -fermentation as a viable strategy for long-term increases in biomass or if it more usefully provides a neat short-term adaptation to anoxia. Fusarium oxysporum is also able to grow using sulphur as an exogenous electron acceptor, too, in a pathway that is likely to share the same enzymes for ATP production as NH 3 fermentation (Abe et al. 2007; Zhou et al. 2002). "
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    • "This puzzle of the production of acetate does not, however, have too many biochemical parts, as only a handful of enzymes is involved . There are of course cases where eukaryotic acetate production might harbour additional surprises, for example in the ascomycete Fusarium oxysporum, that will grow under anaerobic conditions on a variety of reduced carbon sources using elemental sulphur as the terminal electron acceptor, generating H 2 S as the reduced end product in a 2:1 molar ratio relative to acetate (Abe et al., 2007). "
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