Metagenomic Analysis of Biocide-Treated Neotropical Oil Reservoir Water Unveils Microdiversity of Thermophile Tepidiphilus.

Microorganisms are capable of colonizing extreme environments like deep biosphere and oil reservoirs. The prokaryotes diversity in exploited oil reservoirs is composed of indigenous microbial communities and artificially introduced microbes. In the present work, high throughput sequencing techniques were applied to analyze the microbial community from the injected and produced water in a neotropical hyper-thermophile oil reservoir located in the Orinoquia region of Colombia, South America. Tepidiphilus is the dominant bacteria found in both injection and produced waters. The produced water has a higher microbial richness and exhibits a Tepidiphilus microdiversity. The reservoir injected water is recycled and treated with the biocides glutaraldehyde and tetrakis-hydroxymethyl-phosphonium sulfate (THPS) to reduce microbial load. This process reduces microbial richness and selects a single Tepidiphilus genome (T. sp. UDEAICP_D1) as the dominant isolate. Thermus and Hydrogenobacter were subdominants in both water systems. Phylogenomic analysis of the injection water dominant Tepidiphilus positioned it as an independent branch outside T. succinatimandens and T. thermophilus lineage. Comparative analysis of the Tepidiphilus genomes revealed several genes that might be related to the biocide-resistant phenotype and the tolerance to the stress conditions imposed inside the oil well, like RND efflux pumps and type II toxin-antitoxin systems. Comparing the abundance of Tepidiphilus protein-coding genes in both water systems shows that the biocide selected Tepidiphilus sp. UDEAICP_D1 genome has enriched genes annotated as ABC-2 type transporter, ABC transporter, Methionine biosynthesis protein MetW, Glycosyltransferases, and two-component system NarL.

Biofilm formation and its effects on microbiologically influenced corrosion of carbon steel in oilfield injection water via electrochemical techniques and scanning electron microscopy.

In this study, changes in the electrochemical conditions of oil fields caused by biofilms with sulfate-reducing bacteria have been studied as they promote localized pitting damage, reservoir souring problems, and many other processes including well plugging that lead to increased production costs. Biofilm formation and its effects on 1020 carbon steel surfaces were evaluated in a discontinuous electrochemical reactor by using a bacterial consortium isolated from the injection water of a Colombian oil field. Sulfide concentration and pH values were observed to decrease, which was consistent with the exponential planktonic sulfate-reducing bacterial growth. The formation of a biofilm that adheres to a porous layer of corrosion products was identified using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The morphology of the films revealed the presence of the biofilm and corrosion product crystals. Open circuit potential presented a negative shift in the potential during the first 24 h in a biotic cell. Electrochemical impedance spectroscopy showed a change in the behavior of the resistive zone for both systems, a charge transfer trend in the abiotic cell, and a transformation of the charge transfer process to a diffusive process in the biotic cell after 48 h. The polarization resistance showed its lowest resistivity 74.95 Ω·cm-2 during the first 48 h, while the corrosion rate was estimated as 3.37 mpy. This research contributes to the understanding of corrosion mechanisms in the metal-solution interface via detailed monitoring of biofilm growth.