Media for the detection of sulphide-producing bacteria in industrial water systems

Abstract

The importance of sulphate-reducing bacteria (SRB) in microbiological induced corrosion (MIC) has been widely recognized for many years [1]. There are many formulations of culture media used for enumerating SRB [2,3]. Previous studies indicated that viable count procedures underestimated the in situ population by a factor of approximately 1000 compared to in situ sulphate reduction activity [1,4]. The aim of this study was to evaluate different isolation media and carbon sources for the isolation and detection of SRB in South African industrial water systems. Modified iron sulphite (IS) medium yielded the highest numbers when used to enumerate SRB from pure cultures and industrial water samples. When comparing API, SABS, IS, Oxoid and modified synthetic medium using pure cultures of Desulfovibrio desulfuricans IS-medium gave a 12.1%, 40%, 53.3% and 60.3% higher recovery than SABS-, Postgate-, API- and synthetic medium, respectively ( p < 0.05). IS-medium gave a 20.1%, 61.8% and 100% higher recovery than SABS-, API- and Oxoid medium, respectively, when using pure cultures of Desulfotomaculum orientis ( p < 0.05). The dominant sulphide-producing bacteria isolated from the industry using IS-medium were facultative aerobic gram-negative rods that were able to produce sulphide from sulphite under strictly anaerobic conditions. IS-medium was therefore not selective for SRB only. H 2S-producing bacteria that utilized lactate, acetate, formate or palmitic acid as different carbon sources were also isolated from industrial water samples when using synthetic medium.