Physiology and ecology of the sulphate-reducing bacteria.

Abstract

All plants, animals and bacteria require sulphur for the synthesis of proteins. The biological trans- formation of sulphur in natural environments is a nutrient cycling process comprising both aerobic and anaerobic components (Postgate 1984). In its highest oxidation state, sulphur exists as the sul- phate ion (SO:-) which is reduced to sulphide (Sz-) by most bacteria, fungi and plants before incor- poration into amino acids. This process is termed assimilatory sulphate reduction and is purely a biosynthetic process. However, any sulphur compound with an oxidation state above that of sulphide 2) can potentially function as an electron acceptor for the oxidation of carbon substrates by bio- logical processes (Goldhaber & Kaplan 1974). For example, during dissimilatory sulphate reduction, the sulphate ion is utilized as an oxidant for the degradation of organic material. An equivalent amount of sulphide is formed per mole of sulphate reduced (Berner 1974):

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