The effect of a complex bacterial consortium present as a biofilm or as planktonic population on marine corrosion of 1020 carbon steel

摘要

Mechanisms by which microbial biofilms influence electrochemical processes are studied extensively. The necessity of contact between microbial cells and the surface has been demonstrated as prerequisite to microbially influenced corrosion (MIC) and sampling of a biofilm population is advocated as a way of diagnosing MIC. There is, a tendency to implicate MIC in corrosion failures based solely on examining planktonic bacterial population. Here presented laboratory study, carried out using stationary bioreactors, aimed to differentiate between carbon steel corrosion in seawater in the presence of bacterial metabolic products alone, i.e. bacterial cells were kept in planktonic state, and that resulting from the growth of a biofilm. Electrochemical measurements, new generation sequencing (NSG), metabolomics and imaging methods confirmed that corrosion is exacerbated when biotic biofilm components, i.e. living sessile cells interact with the metal surface. Metabolomes of biofilm and planktonic bacterial populations differed and so did mineralogical composition of corrosion products and the type of corrosion attack on colonized and biofilm-free surfaces. High molecular weight lipids dominated biofilm metabolome. This investigation confirmed that biofilm sampling is invaluable in establishing MIC as a cause of metal failure in marine environments. However, the investigation also revealed that caution needs to be exercised when interpreting NSG data in the context of MIC.