Dominance of Pseudomonas in bacterial community and inhibition of fumarate addition pathway by injection of nutrients in oil reservoir revealed by functional gene and their transcript analyses

Abstract

The microbial community composition in subsurface oil reservoirs is responsible for the biogeochemical reactions of hydrocarbon transformation. In this study, the composition, major functions and gene expression activity of the microorganisms in production water from an oil reservoir were analyzed prior to and after injection nutrients using high-throughput 16S rRNA gene sequencing, functional gene and their transcript profiling. Pseudomonas spp. was the dominant bacteria showing a quick increase in the bacterial population. The injection of nutrients lowered the activity of assA-bearing bacteria, but accelerated the activity of methanogens. The results show that the anaerobic hydrocarbon degradation was actively occurring in situ oil reservoir sampled, Smithella was the active anaerobic hydrocarbon degrading bacteria, and Methanoculleus and Methanothrix were the actively dominant methanogens. The present study provides a snapshot of the practical technology with insightful results to support the research, development and utilization of reservoir through biological augmentation.