Bisulfite reductase and nitrogenase genes retrieved from biocorrosive bacteria in saline produced waters of offshore oil recovery facilities

Water-flooding is a common strategy to enhance oil recovery in reservoirs. Maintaining quality and standards of produced water avoids oil biodegradation, biogenic souring and biocorrosion during operations, which are influenced by sulfate-reducing (SRB) and Fe (III) reducing bacteria. The aim of this work was to increase our knowledge of corrosive bacterial communities inhabiting saline produced waters of offshore oil exploitation facilities through retrieving sequences of functional genes, for instance, dsrAB and nifD of Desulfovibrionales, Desulfobacterales and Desulfuromonadales taxonomical orders. Five clone libraries were generated with retrieved sequences acquired from different saline produced waters, with and without biocide dosing. The dsrAB phylogenetic analyses showed Desulfomicrobium, Desulfovibrio, and Desulfohalobium as well as Desulfococcus, Desulfosarcina, Desulfobacter, Desulfobacterium and Desulfobulbus. The retrieved nifD genes displayed the Fe (III) reducing bacteria (Desulfuromonadales) such as Desulfuromusa, Pelobacter, Malonomonas, and Desulfuromonas. The relative abundance in all waters was: the Desulfovibrionales were represented by 55.28% of analyzed clones; the Desulfobacterales by 26.83% and 17.89% for the Desulfuromonadales. Diversity measures were calculated by the Shannon index (H'), which showed that there was a high degree of diversity between all produced waters; however, dominance in produced water with biocide was detected by a Desulfovibrio taxon.