Methane as a Minor Product of Pyruvate Metabolism by Sulphate-reducing and Other Bacteria

Abstract

SUMMARYDisrupted cells of some Desulfovibrio species, of Desulfotomaculum ruminis and of certain other anaerobes produced methane as a minor product of pyruvic phosphoroclasm. In one Desulfovibrio species the reaction, which was not specially sensitive to air, involved vitamin BI2, coenzyme A, thiamine pyrophosphate, magnesium ions and acetyl phosphate. Adenine and other nucleotides stimulated the reaction; a mixture of ATP and AMP was most effective. Methionine stimulated the reaction but the other methyl donors did not. In optimal conditions methane accounted for 0.1 to 0.02 mole % of the pyruvate metabolized, formed at 20 to 30 nl.CH,/mg. bacterial protein/hr. Tests in D20 indicated that the methane came from the methyl-carbon of pyruvate ; correspondingly, ethane formation from a-ketobutyrate was detected. I N T R O D U C T I O NSisler & ZoBell (I 95 I) reported that certain cultures of marine sulphate-reducing bacteria, pure by normal criteria, formed methane during growth in lactate + sulphate media. Though occasional references to this finding have appeared, and Sorokin (1956) failed to conlirm it, interest has tended to centre on the disputed question of the oxidation of methane (and other hydrocarbons) by desulfovibrios (e.g. Sorokin, 1957 ;Davis & Yarbrough, 1966). Methane formation by phosphoroclastic preparations from strains of sulphate-reducing bacteria was reported briefly by Postgate (I 969). The present paper describes the reaction in one Desulfovibrio strain in more detail and reports its occurrence in other bacteria. METHODSCultivation. Desulfovibrio desulfuricans ;variety azotovorans, strain BERRE s (NCIB 8388) was grown at 30" in a 600 ml. continuous-culture apparatus (Baker, 1968) at dilution rates ranging from 0.05 to 0.1 hr-l. The medium used was deficient in k e d nitrogen ; it contained (g./l.) : KH2P04, 0.5 ; Na,S04 4-5 ; CaCl, . 2H,O, 0.06 ; MgSO, . 7H20, 0.06; FeSO,. 7H20, 0.004; sodium lactate, 6; sodium citrate, 0.3 (to prevent precipitation of metal hydroxides) in distilled water; plus 10 ml. of a trace element mixture containing (mg.) : H8B08, 2'32; CoSO, . 7H20, 95-6; CuSO, . 5H20, 8 ; MnSO, . 4H20, 8 ; NaMoO, .2H,O, 30 ; ZnSO, . 7H20, 174 in I 1. distilled water. The complete medium was at pH 8-2; the atmosphere was N, containing 6 to 8% (v/v) CO,.The CO, buffered the culture to between pH 7.6 and 8, and displaced excess sulphide.

The marine geochemistry of methane

“…Postgate (1969) has found that sulfate reducing bacteria produce methane from the methyl carbon of pyruvate, a mechanism very different from that used by methane bacteria (Gunsalus et al, 1976 I have. performed several experiments using cultures of marine algae to determine whether these organisms might be an important methane source.…”

“…However, data of Winfrey and Zeikus (1977) show that some methane production does continue to occur. The source of this methane is unknown, but may be either methanogenic bacteria or sulfate reducers which produce methane as a trace byproduct (Postgate, 1969).…”

Anaerobic methane oxidation in sulfate depleted sediments: effects of sulfate and molybdate additions

“…For example, Desulfovib-1-20 desulfuricans CO-oxidizes methane in the presence of another electron donor, e.g. pyruvate (Davis & Yarborough 1966), but is unable to grolv on methane alone (Sorokin 1957, Postgate 1969. Iversen (1984) calculated that 0.3% of the sulfate reduction in pure cultures of 3 Desulfovibrio strains grown in the presence of pyruvate and methane could be accounted for by methane oxidation.…”

Anaerobic methane oxidation rates at the sulfate‐methane transition in marine sediments from Kattegat and Skagerrak (Denmark)1

“…One species of sulfate 944 reducer, Desulfovibrio desulfuricans, can co-tation area; the depth was 65 m and the oxidize [14C]methane when growing on lac-sedimentation rate was 0.16 cm yr-l. Statate (Davis and Yarborough 1966), but can-tion C was in Skagerrak at 200-m depth and not grow with methane as the sole carbon had the highest sedimentation rate, 0.29 cm source (Sorokin 1957;Postgate 1969). Sul-yr-l .…”