Molecular diversity of bacterial bamA gene involved in anaerobic degradation of aromatic hydrocarbons in mesophilic petroleum reservoirs

• The diversity of bamA genes found in oil reservoir produced water was higher than previous reports.
• The bamA genes related to nitrate reducing bacteria indicates the potential for Microbial Enhanced Oil Recovery application.
• Firmicutes (Desulfotomaculum spp.) may be important aromatic hydrocarbons degraders in both oil wells.

Aromatic hydrocarbons are usually metabolized to the central intermediate benzoyl-coenzyme A (CoA) prior to ring cleavage. 6-Oxocyclohex-1-ene-1-carbonyl-CoA hydrolase, a key enzyme involved in the reductive benzene ring cleavage, encoded by the bamA gene can serve as a functional biomarker for detecting anaerobic degradation of aromatic compounds in different environments. In the present study, we examined the diversity the bacterial bamA gene in oil field. We sequenced bamA fragments that were PCR amplified from the microbial biomass of two mesophilic oil producing reservoirs during a period of four months. The results showed the presence and a higher diversity of bamA gene than previous studies, indicating its potential involvement in degrading aromatic hydrocarbons through anaerobic biochemical pathways in oil fields. The bamA gene sequences were affiliated to bacteria that are known to degrade aromatics, including Azoarcus, Georgfuchsia, Sulfuritalea, Peptococcaceae and Syntrophus. Differences of composition and diversity of bamA gene sequences over a period of four months in these oil reservoirs showed that it is necessary to monitor functional genes over a period of time to fully establish their significance to any specific process at any site.