A Thermodynamic Assessment of Possible Substrates for Sulphate-reducing Bacteria

Abstract

A thermodynamic feasibility study was applied as a means of predicting suitable energy-yielding substrates for growth of sulphate-reducing microorganisms. The average free energy release per electron pair for a substrate-sulphate oxidoreduction may be more or less than the energy requirement for ATP synthesis from ADP and Pi. Substrates were divided into two groups on this thermodynamic basis and the division was shown to accord with previous experimental reports; those substrates which released an average of at least 8� 4 kcal per electron pair (35�2 kJ per electron pair) were able to support growth whilst those releasing less than 8� 4 kcal were unable to do so. It is proposed that the thermodynamic assessment could be applied to a wide range of possible substrates to predict the likelihood of their serving as sole substrates for growth of these organisms.

Big Soda Lake (Nevada). 3. Pelagic methanogenesis and anaerobic methane oxidation1

“…The involvement of sulfate reduction in anaerobic methane oxidation has been discussed previously. Thermodynamic calcu-0.0 l-0.06% of sulfate reduction, although lations indicate that oxidation of methane by sulfate-reducing bacteria is slightly favorable (Martens and Berner 1977;Wake ' methane may fuel sulfate reduction occur-et al 1977), and a similar asscssmcnt can be made for conditions in Big Soda Lake.…”

“…In all of these reports methane could not serve as the sole carbon source for growth of the organisms. The latter is not surprising because of the poor energy yield involved in the oxidation (Wake et al 1977). On the other hand, Zehndcr and Brock (1979) suggested that methanogenie bacteria were responsible for methane oxidation.…”

Sulfate‐reducing bacteria

“…108 It was estimated that an energy of at least 35 kJ for every two electrons transferred was necessary to support the growth of Desulfovibrio or Desulfotomaculum. 106 SRB metabolic reactions and free-energy changes with different substrates are shown in Table 2.…”

Effect of soil redox conditions on microbial oxidation of organic matter

“…This process involves the oxidation of substrate C (electron donor) and transfer of electrons to SO~-(electron acceptor), a process termed as dissimilatory SO~respiration. The oxidation of organic matter during SO~reduction does not proceed beyond the level of acetate (153). The metabolism of sulfur in anaerobic systems has been the subject of recent reviews by Krouse and McCready (67), Thauer and Badziong (145), and Trudinger (149).…”