Differential media for sulphur bacteria

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Abstract
Sulphur bacteria in general are readily obtained as a crude ‘sulphuretum’ in Winogradsky's columns which consist of a slurry of powdered cellulose and gypsum beneath a mineral salt solution. Sulphate‐reducing bacteria are best detected in fluid media incubated anaerobically, containing lactate, sulphate, mineral salts and ferrous ammonium sulphate. Blackening due to FeS indicates sulphate reduction. A nutrient agar containing sodium sulphite and iron citrate has been used for Clostridium nigrificans. These media do not have appropriate Eh values for optimum growth of the organisms and only detect them if large numbers are present. Quantitative procedures are only available for Desulphovibrio desulphuricans. Sulphur‐oxidising bacteria are best detected by the pH changes they induce in media of mineral salts and either elemental sulphur or sodium thiosulphate. Anaerobic sulphide‐oxidising bacteria are best obtained in illuminated media of mineral salts and H2S, incubated anaerobically. the initial pH value and sulphide concentration determine the type obtained. Aerobic sulphide‐oxidising bacteria are sometimes found in Winogradsky's columns, but effective differential media are not available.