HYDROGEN SULFIDE PRODUCTION BY SYNECHOCOCCUS LIVIDUS Y52‐s1

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Abstract
SUMMARY: Under anaerobic conditions and in the absence of CO2, the thermophilic blue‐green alga Synechococcus lividus Y52‐s, evolved hydrogen sulfide in both darkness and light. The mechanism of this process was investigated and compared with photo‐ and dark reductions in organisms representing several phyla. The photoproduction of H2S from either sulfate or thiosulfate was inhibited by 3‐(3,4‐dichlorophenyl)‐1, 1‐dimethyl urea (DCMU) and carbonyl m‐chlorophenyl‐hydrazone (m‐Cl‐CCP). The inhibitory effect of DCMU showed the requirement for photosystem II as electron donor. Inhibition by m‐Cl‐CCP also implicated ATP as an energy source. Monofluoroacetate partially inhibited photoproduction of H2S. This indicated that oxidative metabolism may act us a source of electrons to reduce the photooxidant under certain conditions. Thiosulfate acts only as electron acceptor and is reductively cleaved to S= and SO3=. Thiosulfate and sulfate appeared to replace CO2 in the light and O2 in darkness as electron acceptors. The phosphorylation uncouplers dinitrophenol and m‐Cl‐CCP stimulated dark H2S production.