Hydrogen oxidising bacteria

Phosphatidylcholine and analogues.- Phosphatidylcholine, the most abundant phospholipid in eucaryotes, is generally absent from bacte ia. It has now been shown that it is a major constituent of the lipids fi om several species of a variety of genera of hydrogen-oxidising bacteria, although it is not always present in... 

Hydrogen sulfide can be oxidised to elemental sulfur, for example, by green and purple sulfur bacteria. Further oxidation of elemental sulfur by sulfur oxidising bacteria can produce sulfate. 

The Sulphur Cycle.— Unlike phosphorus, sulphur appears in both oxidised and reduced forms in the history of life. Completely oxidised as sulphate, it enters the plant from the soil, and is converted into partially reduced organic compounds containing the thiol group —SH or the disulphide linkage —S—S—. From these, the completely reduced form, HjS, is derived by bacterial degradation either in the soil or in the alimentary tract of the animal. Hydrogen sulphide is attacked by the sulphur-oxidising bacteria, with the ultimate formation of sulphate, which is available for plant absorption. 

Hydrogen sulphide This is produced by the putrefaction of organic sulphur compounds or by the action of sulphate-reducing bacteria in anaerobic conditions (e.g. in polluted river estuaries). It is fairly rapidly oxidised to SOj and concentrations are considerably lower than those of (Table 2.6). Nevertheless it is responsible for the tarnishing of copper and silver at normal atmospheric concentrations. 

The inter-dependency of bacterial species has been described for a number of cases. One example is the close dependency of sulphate-reducing bacteria on the presence of an associated heterotrophic microflora which supply the bacteria with additional growth factors and favour reduction of the medium (Cahet, 1965, 1966 LeGall and Postgate, 1974). Moreover, the production of hydrogen sulphide binds them to sulpho-oxidisers within the ecosystem (called sulphuretum by Baas-Becking, 1925). 

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