Sulfate-Reducing Bacteria Isolated from an Oil Field in Kazakhstan and a Description of Pseudodesulfovibrio karagichevae sp. nov.

Sulfidogenic bacteria cause numerous issues in the oil industry since they produce sulfide, corroding steel equipment, reducing oil quality, and worsening the environmental conditions in oil fields. The purpose of this work was to isolate and taxonomically identify the sulfidogenic bacteria responsible for the corrosion of steel equipment at the Karazhanbas oil field (Kazakhstan). In this study, we characterized five sulfidogenic strains of the genera <i>Pseudodesulfovibrio</i>, <i>Oleidesulfovibrio</i>, and <i>Acetobacterium</i> isolated from the formation water of the Karazhanbas oil field (Kazakhstan). Sulfate-reducing strain 9FUS^T revealed 98.9% similarity of the 16S rRNA gene sequence with the closely related strain '<i>Pseudodesulfovibrio methanolicus</i>' 5S69^T and was studied in detail to enhance the taxonomic resolution. Strain 9FUS^T grew optimally at 23-28 °C, pH 6.5, and 0-2% (<i>w</i>/<i>v</i>) NaCl. The strain used lactate, pyruvate, methanol, ethanol, fructose, ribose, and H₂/CO₂ (in the presence of acetate) as carbon and energy sources for sulfate reduction. <i>Iso</i>-C_17:1 ω11, C_15:0, <i>iso</i>-C_15:0, and C_16:0 were the predominant fatty acids. The genome is 4.20 Mbp with a G + C content of 64.0%. The average nucleotide identity and digital DNA-DNA hybridization values with <i>Pseudodesulfovibrio</i> spp. genomes were 72.5-91.6% (<95%) and 18.5-45.0% (<70%), respectively, and supported our conclusion that 9FUS^T (=VKM B-3654^T = KCTC 25498^T) belonged to a novel <i>Pseudodesulfovibrio</i> species, for which the name <i>Pseudodesulfovibrio karagichevae</i> sp. nov. is proposed. Pangenome analysis of sixteen <i>Pseudodesulfovibrio</i> species and functional annotation analysis of identified genes revealed complete modules of enzymes of the main metabolic pathways, characteristic of bacteria of this genus, and unique genes highlighting the adaptations of strain 9FUS^T in carbohydrate metabolism, nutrient uptake, and environmental stress response. Isolation of these strains expands our understanding of the diversity of sulfidogens in oil reservoirs and can be used to test the effectiveness of biocides used in an oil field.