ABSTRACT
Microbially influenced corrosion (MIC) is a well-reported problem in the petrochemical industry, with billions of US dollar losses annually. MIC is often controlled by mechanical scrubbing such as pigging of pipelines, or chemical action by the use of biocides. However, the response of microbes toward the repeated application of biocides has never been properly characterized. In this study, we gain insights into the molecular responses of MIC-associated microbes in the presence of biocides through the characterization of metabolic pathways encoded in the microbes’ DNA. Artificial Sea Water media was inoculated with anaerobic sediment from Galveston Beach, Texas, and then recirculated in an anoxic continuous flow loop embedded with X52 carbon steel coupons. Some flow loops were treated with biocides to prevent biofilm growth; biocide-treated samples had around a mean corrosion rate of 10× less than that of the corrosive samples. The resulting biofilm growth from both the corrosive and biocide-treated samples was harvested, their DNA extracted and then sequenced using Oxford Nanopore long-read sequencing technology. From the sequence data, over 20 high-quality metagenome-assembled genomes (MAGs) were recovered. The corrosive biofilms were dominated by a Desulfocapsa strain, a sulfate-reducing bacterium often targeted as a culprit of MIC. In the biocide-treated samples, the biofilm community structure is more diverse in terms of both richness and evenness. However, a different Desulfocapsa strain was found in the biocide-treated biofilm. Comparing these two different Desulfocapsa strains reveal genes that may contribute to the tolerance of microbes toward external stressors such as the presence of biocides and/or metals. Therefore, there is a possibility that the repeated use of biocides to control MIC may potentially give rise to corrosive microbes that are biocide-tolerant.
