Impact of soil microbial processes on the fate of crude oil contamination: Insights from aerobic and anaerobic microcosms

Niger Delta oil spills significantly impact the local ecosystem, potentially affecting soil microbial communities that are vital for various functional processes, including bioremediation. Here soils from a recent oil spill were used to conduct microcosm experiments under aerobic and anaerobic conditions amended with different terminal electron acceptors (TEAs) to assess the oil contamination bioremediation potential using in situ microbial communities. Results showed a substantial increase in hydrocarbon removal, with the highest removal efficiency observed in aerobic microcosms and anaerobic microcosms when sulfate or iron(III) were used as TEA. In contrast to aerobic conditions anaerobic conditions resulted in the release of Fe and Al into solution. A significant microbial community shift towards known potential oil degraders such as Alphaproteobacteria , Melainabacteria , Gammaproteobacteria, Deltaproteobacteria , Spirochaetia and/or Acidobacteriia was observed, indicating their potential role in oil degradation and resilience despite the toxicity caused by the oil/associated metals. QPCR analysis indicated an increased presence of polycyclic aromatic hydrocarbon ring hydroxylating dioxygenase genes ( PAH-RHDαGN ), confirming the existence of potential PAH-degrading microorganisms. This suggests that targeted PCR analyses could be used to assess the oil contamination extent and evaluate the bioremediation potential of impacted environments. It underscores the importance of a comprehensive indigenous microbial community assessment including their in situ hydrocarbon degradation potential. Comparative microcosms analysis demonstrated that dynamic responses of these communities across environmental settings provide a valuable insight into natural attenuation processes occurring in oil-contaminated soils. Combined, these approaches provide a framework for assessing microbial-driven oil degradation and a guide to develop effective/sustainable bioremediation strategies. • Oil impacted soils used in (an)aerobic microcosms to assess bioremediation potential • Results show increased oil removal with release of metals (Fe and Al) into solution • Shifts in the microbial community present to potential oil degraders • Increased presence of PAH-RHDαGN gene required for degradation of PAHs was observed • Indicated that targeted PCR analyses can be used to assess bioremediation potential