CORROSION-ENHANCING POTENTIAL OF SHEWANELLA-PUTREFACIENS ISOLATED FROM INDUSTRIAL COOLING WATERS

Microbially influenced corrosion (MIC) is catalysed by a series of met abolic activities of selected micro-organisms, notably by oxidation of cathodic hydrogen by hydrogenase, by hydrogen sulphide and by reducti on of ferric iron. The sulphate-reducing bacteria are considered to be the most common catalyst of MIG, whereas the role of other bacteria h as been neglected. This study examined the corrosive potential of the facultative sulphide producer, Shewanella putrefaciens, isolated from an industrial cooling water system. Shewanella putrefaciens was shown to reduce ferric iron and sulphite under anaerobic conditions and with ferric iron being the preferred electron acceptor. The isolate could utilize cathodic hydrogen as an energy source, especially when using s ulphite as a terminal electron acceptor. In pure culture corrosion exp eriments, the highest mass loss of mild steel was observed in the pres ence of sulphite as sole electron acceptor, although mass loss was als o detected where ferric iron was the sole electron acceptor. Our data indicate that S. putefaciens plays a role in MIC as it was able to cat alyse a variety of corrosion-promoting reactions and to corrode mild s teel under pure culture conditions.