Purifying a corrosive hydrocarbon-degrading Shewanella indica from iron rust in oil-containing seawater: Understanding of microbial corrosion mechanisms based on whole genome analysis.

Corrosion products covering corroded steels immersed in oil-contaminated seawater for 465 days were analyzed for genomic, microbial activity, mineral, and morphology. Compared to 85 days of immersion, abundant chemolithotrophic bacteria predominantly attached to corroded steel, while the abundance of hydrocarbon-degrading bacteria display a downward trend (like Alcanivorax dropped from 3.2% to 0%, Marinobacter from 1.3% to 0.99%). S. indica, isolated from the outer rust layer, exhibited crude oil emulsification and potential hydrocarbon-utilizing capacity (oil droplet diameter decreased from 15.4 to 7.0 μm). Whole genome analysis showed S. indica's potential for flagellar synthesis, hydrocarbon degradation, and phosphate conversion, consistent with its isolation from an oil-contaminated corrosion environment. Microbial acidification (pH < 6.0) accelerated X70 steel corrosion within 7 days (Pitmax = 29.77 μm, 5.4 times that of the sterile system). Humic acid or limited crude oil content indeed inhibited microbial corrosion by scaling and disrupting rust-microbe interactions. Available carbon sources supported microbial growth and vivianite formation. This study aims to elucidate the corrosion mechanisms of hydrocarbon-degrading bacteria in marine oil-water environments, using the isolated S. indica in rust as a model.