Competitive and Non-competitive Inhibitors of Bacterial Sulphate Reduction

Abstract

SUMMARY:The selenate ion, a remarkably powerful competitive antagonist of the reduction of sulphate by Desulphovibrio desulphuricans (Hildenborough) suspensions, did not affect reduction of sulphite and thiosulphate. Cysteine, methionine and glutathione had no anti-selenate effect. Selenate also inhibited the growth of D. desulphuricans ; this effect was antagonized competitively by sulphate and noncompetitively by sulphite. Repeated subculture in subinhibitory selenate + sulphate mixtures did not give rise to a selenate-resistant strain, though selenium was deposited in these conditions.The monofluorophosphate ion behaved similarly : it was a competitive sulphate antagonist in growth and in sulphate reduction, though it had a lower specific antisulphate activity than selenate. It did not affect the metabolism of sulphite or thiosulphate. At high concentrations it showed non-competitive inhibition of sulphate reduction.Of the other 'analogues' of sulphate tested, potassium tellurate suspensions and chromate inhibited growth and sulphate reduction, but were not competitive sulphate antagonists. High concentrations of perchlorate depressed sulphate reduction in a non-competitive manner, and methanesulphonate, P-hydroxyethanesulphonate, benzenesulphonate, ethylsulphate, sulphamate and dimethylsulphone were inactive.An acridinium dye known to inhibit the growth of D. desuZphuricans did not affect sulphate reduction, and, in growth, was not antagonized by sulphate or complex nitrogenous supplements. The organism was readily ' trained' to resist this dye. Butlin, 1949). Hence the inhibition of these bacteria has been studied largely from a practical standpoint. Rogers (1940) investigated the resistance of crude cultures to various dyestuffs and observed that acriflavine and proflavine were their most active inhibitors. He studied in detail a dye of the acridinium group, '914', and showed that its activity depended on inoculum size. He noted the possibility that adaptation to resist the dyestuff could take place, and a further publication (Rogers, 1945) described the practical use of the dye. Bunker (1942) advocated decrease of pH value to control the pollution of relatively small water volumes by sulphate reducers. Allen (1949) confirmed this in a study of their activities in sewage, mentioned their high resistance to chlorine and showed that various nitro-compounds depressed H,S formation. The resistance of these organisms Inhibition of sulphate redutcers 129 to many common inhibitors and antibiotics has been studied (Chemistry Research, 1947, and an effect of ferrous ions in enhancing this resistance was mentioned (Chemistry Research, 1947). This effect could be partly due to differences between the methods used to detect growth in these experiments : blackening of the culture by ferrous sulphide formation can occur at levels of growth undetectable by direct inspection. Postgate (1949) described the competitive inhibition of sodium sulphate reduction by sodium selenate, using a non-growing cell suspension, and sho...

Linked Redox Precipitation of Sulfur and Seleniumunder Anaerobic Conditions by Sulfate-Reducing BacterialBiofilms

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The Examination of Sulphur Auxotrophs: A Warning

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