Physiology and Genomic Characteristics of Geotoga petraea, a Bacterium Isolated from a Low-Temperature Petroleum Reservoir (Russia)

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Members of the order Thermotogales often occur in high-temperature oilfields. They possess a toga, a characteristic external sheath. Members of the genus Geotoga have been as yet isolated only from oilfields and are represented by three strains with unsequenced genomes. The information on the intraspecific phenotypic diversity is scarce. An enrichment growing anaerobically on oil was obtained from formation water of the Vostochno-Anzirskoe oilfield (Russia). High-throughput sequencing of the V3–V4 region of the 16S rRNA genes revealed the enrichment to contain members of the genera Tangfeifania (51% of the total number of sequences), Halanaerobium (36%), Arcobacter (10%), and Geotoga (3%). Strain HO-Geo1 isolated from this enrichment belonged to the known species Geotoga petraea (99.2% similarity of the 16S rRNA gene sequences). The cells were motile rods surrounded by sheaths. They grew anaerobically, fermented carbohydrates and proteins producing acetate, H₂, and СО₂, and reduced thiosulfate and elemental sulfur to sulfide. In pure culture the strain did not grow on oil. Growth occurred within broad ranges of temperature (24–55°C, optimum at 47–50°C) and salinity (0.2–140 g/L, optimum at 20–40 g/L), which was in agreement with conditions of the low-temperature oilfield with highly mineralized formation water. The genome of strain HO-Geo1 (~2.15 Mb) contained 2057 genes, most of which were involved in protein, amino acid, and carbohydrate metabolism. High salt-tolerance of strain HO-Geo1 depended on the genes of adaptation to hyperosmotic stress. H₂ formation was determined by the presence of the genes encoding all four subunits of NADP-dependent dehydrogenase. In oilfields, members of the genus Geotoga probably utilize microbial biomass and the products of oil biodegradation formed by other microorganisms. They may be involved in corrosion of metal oilfield equipment.