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Summary: There are many strains and perhaps several species of sulphate-reducing bacteria. They may be isolated by using a variety of media over a wide range of temperature. Crude cultures are readily obtained, but isolation of absolutely pure cultures is usually difficult. Considerable simplification in procedure may sometimes be effected by including 3% Na2SO3.7H2O in the media; the sulphite eliminates most of the contaminating organisms in crude cultures and facilitates subsequent purification. A method of maintaining stock cultures on sterile clay is preferred to the use of artificial media.
No growth takes place in media rendered ‘biologically free’ of iron, but the traces normally present in media constituents as impurities are sufficient for good development. Rapid and abundant growth free from ferrous sulphide has been obtained in a mineral salts + lactate + yeast extract medium containing ferrous ions below the saturation concentration for ferrous sulphide.
One thermophilic and four mesophilie strains have been shown to be facultative autotrophs, using the oxidation of hydrogen as energy source, with sulphate, sulphite, thiosulphate and elementary sulphur as hydrogen acceptors. No autotrophic growth takes place in the absence of hydrogen. Hydrogen can be provided in vitro by immersing metallic iron in the medium.