Abstract. Microorganisms in petroleum reservoirs play significant roles in hydrocarbon
degradation, and through the terminal electron-accepting process of
methanogenesis, they also contribute to microbially enhanced oil recovery
(MEOR) worldwide, with great economic and environmental benefits. Here, a
molecular investigation, using the 16S rRNA and mcrA gene profiles based on
MiSeq sequencing and clone library construction methods, was conducted on
oil and water (aqueous) phases of samples of high (82–88 ∘C),
moderate (45–63 ∘C), and low temperatures (21–32 ∘C) from
seven petroleum reservoirs in China. A core bacterial microbiome with a
small proportion of shared operational taxonomic unit (OTU) values, but a high
proportion of sequences among all reservoirs was discovered, including
aerobic degraders, sulfate- and nitrate-reducing bacteria, fermentative bacteria,
and sulfur-oxidizing bacteria distributed mainly in Proteobacteria, Bacteroidetes, Deferribacteres,
Deinococcus–Thermus, Firmicutes, Spirochaetes, and Thermotogae. Their prevalence in the previously reported petroleum reservoirs
and successive enrichment cultures suggests their common roles and functions
involved in aliphatic and aromatic hydrocarbon degradation. The methanogenic
process generally shifts from the dominant hydrogenotrophic pathway in the
aqueous phase to the acetoclastic pathway in the oil phase in high-temperature
reservoirs, but the opposite was true for low-temperature reservoirs. No
difference was detected between the two phases in moderate temperature
reservoirs. Physicochemical factors, including pH; temperature; phase
conditions; and nitrate, Mn2+, and Mg2+ concentrations were the
main factors correlated to the microbial compositional and functional profiles
significantly. Linear discriminant analysis (LDA) effect size (LEfSe) analysis shows distribution
differences of microbial groups towards pH, temperature, and the oil and aqueous
phases. Using the software Tax4Fun for functional profiling indicated
functional metabolism differences between the two phases, including amino
acids, hydrocarbons in the oil phase, and carbohydrates in the aqueous phase.
Microbial Hydrocarbon Degradation: Efforts to Understand Biodegradation in Petroleum Reservoirs
