Biocorrosion causes huge economic losses to the oil and gas industry. Microbes such as sulphate-reducing bacteria (SRBs), acid-producing bacteria (APBs), methanogens, iron-reducing bacteria (IRBs), sulphate-oxidizing bacteria (SOB) are the critical drivers of souring, biofouling, clogging, pitting and bio filming. The use of seawater and wastewater for enhanced oil recovery further exacerbates biocorrosion. This increased biocorrosion is primarily observed in injection wells using the wastewater-seawater. Significant concentrations of biocides are injected to address this. These biocides eventually impose selective pressure on the inherent microbial community and result in the development of resistance against the active compounds. Hence never resulting in total clearance of microbes. Lower biocide efficacy is widely observed in oil and gas industries; however, this is seldomly studied. Molecular approaches are likely to play a significant role in identifying genes conferring biocide resistance and the genetic elements involved in their transfer across other microbial communities.
Biocide resistance was first reported in 19521. There are umpteen reports published in the last 4 decades suggesting bacterial resistance against biocides, similar to antibiotic resistance in bacteria2-5. The situation intensifies when biofilms are present within a system6,7. On the one hand, dense biofilms prevent biocides’ penetration; on the other side, the sessile cells slow down the metabolic rates to reduce the uptake of toxic chemicals. They tend to express proteins that can destroy biocides and discard them from their bodies through efflux channels. The most remarkable phenomenon reported by Xu and Gu is the formation of ‘persister cells’ that preserve themselves during a biocide event and eventually re-grow with stress alleviation6. Brown and group detected multidrug resistance efflux genes regulating the removal of biocides in oil and gas environments8. Oil and gas pipelines are hotspots for biofilms and are most conducive to developing resistance against the selective biocides used for their disruption. The mechanism of action of biocides is poorly understood and call for further research in this area.
