Enrichment and comparative metagenomics of microbes involved in biocorrosion of gas transport or storage steel infrastructure

Biocorrosion, also known as microbiologically influenced corrosion (MIC), is the deterioration of metals caused by microbial activities that compromise the structural integrity, reliability, and safety of steel infrastructure. To identify the genetic determinants that MIC-causing microorganisms may use to attack steel infrastructure, field samples from natural gas infrastructure with a potential history of MIC were collected, enriched for different MIC categories, and subjected to whole-genome shotgun sequencing for metagenomic analysis. Biofilms were grown on carbon steel coupons or glass slides as attachment substrates to assess differences in microbial community composition and metabolic activities. The highest corrosion activities were observed in enrichments dominated by acid-producing bacteria (APB) and hydrogen-utilizing bacteria. APB enrichments resulted in the highest accumulation of organic acids and a severe decrease in culture fluid pH. A total of 57 metagenome-assembled genomes were recovered from the biofilms, some of which differed between carbon steel coupons and glass slide substrates. The metagenomes contained most of the known genes implicated in MIC and sulfide production, with substantial variation in estimated gene copy numbers among metagenomes and attachment substrates. Overall, comparative analysis of these biofilm metagenomes enriched from natural gas production and processing infrastructure highlights similarities to microbial communities commonly observed in oil production and processing systems and provides an overview of candidate genes that may be used as molecular probes for MIC.