Functional microorganisms involved in the sulfur and nitrogen metabolism in production water from a high-temperature offshore petroleum reservoir

Abstract

Microorganisms with diverse metabolic functions inhabit petroleum reservoir systems utilizing multiple electron acceptors, but current understanding about the composition and diversity of functional microbial community in offshore oilfields is still scarce. In this study, the diversity, phylogenetic distribution and abundance of microbes involved in the sulfur (S) and nitrogen (N) metabolisms in production water of a high-temperature offshore oilfield were described selectively based on the functional gene analysis using polymerase chain reaction (PCR) technique. The detected sulfate-reducing prokaryotes (SRP) were affiliated with δ-Proteobacteria, Thermodesulfobacteria, Nitrospira, Firmicutes and Euryarchaeota, and the key and dominant SRP in the two samples included the genera Archaeoglobus, Thermodesulfobacterium, Thermodesulfovibrio, Thermodesulforhabdus and Desulfomicrobium. The sulfur-oxidizing prokaryotes (SOP) belonged to α-, β- and γ-Proteobacteria, mainly represented by Roseovarius, Rhizobium, Methylobacterium, Thiobacillus and Thauera genera. In addition, the nitrate-reducing and denitrifying communities were composed of α-, β- and γ-Proteobacteria, among which Bosea, Pseudomonas, Marinobacter, Diaphorobacter and Mesorhizobium showed a relatively high abundance. The quantitative PCR results revealed that functional gene abundances of N metabolism (the napA, nirS and nosZ genes) were mostly higher than those of S metabolism (the aprA, dsrA, dsrB and soxB genes), and functional gene abundances in sample X1 were mostly higher than those in sample X2. This work provides basic data for the understanding of diversity, composition and distribution of functional microorganisms in offshore petroleum reservoir ecosystems, and also mitigation of the reservoir souring and control.