Distribution of Shewanella putrefaciens and Desulfovibrio vulgaris in sulphidogenic biofilms of industrial cooling water systems determined by fluorescent in situ hybridisation

Limited research has been done on the distribution and role of sulphidogenic facultative anaerobes within biofilms in microbially influenced corrosion (MIC). Sulphate-reducing bacteria (SRB) cause MIC and occur in the anaerobic zone of multispecies biofilms. Laboratory-grown multispecies biofilms irrigated with sulphate or sulphite-containing synthetic cooling water, and biofilms from an open simulated cooling water system, were hybridised with a rhodamine-labeled probe SPN3 (Shewanella putrefaciens) and fluorescein-labeled probe SRB385 (Desulfovibrio vulgaris) and investigated using scanning confocal laser microscopy. The facultative anaerobe S. putrefaciens and the strict anaerobe D. vulgaris synergistically coexisted in multispecies biofilms, but as time progressed, S. putrefaciens flourished, displacing D. vulgaris. The results show that S. putrefaciens is capable of growing in sulphidogenic biofilms in aerated environments such as industrial cooling water systems, colonising sulphidogenic biofilms and out-competing the true sulphate-reducing bacteria.