Isolation, identification and metabolic characterization of an anaerobic thermophilic bacterium

Abstract:

[Objective] To isolate, protect thermophilic microbial resources from petroleum reservoirs and analyze these main metabolic characterization. [Methods] The strain BF1 was isolated by Hungte anaerobic technique from Chenghai 1 Unit of Dagang oil field in China. Its taxonomic status determined by physiological, biochemical and 16S rRNA gene sequence analysis. Its effect of sulfur metabolism on the corrosion current was measured by electrochemical analysis. [Results] The strain BF1 was Gram-negative, strictly thermophilic anaerobic, top-sporulating, non-motile, rods, 0.42 μm×(1.6?5.4) μm, grew solitary, in pairs or in chains. Growth occurred at 45 °C?75 °C (optimum 60 °C), at pH 4.5?8.5 (optimum 6.5). Specific growth rate (μm) was 0.99 h?1 and doubling time was 42 min. Substrates included glucose, melizitose, raffinose, mannose, lactose, fructose and ribose. The main products of glucose fermentation were CO2, H2, acetate and ethanol. The strain could reduce thiosulfate and sulfite to sulfide, and its tolerance limits were 75 mmol/L and 50 mmol/L, respectively. The electrochemical impedance reduced from 2 099 Ω/cm2 to 776 Ω/cm2 and the corrosion current increased from 9.936e-006 A to 3.25e-005 A after thiosulfate (50 mmol/L) was reduced. The fatty acids were mainly composed of saturated long chain fatty acids, with C15:0 the most, accounting for 70.6%. The G+C content of DNA was 34.0 mol%. The 16S rRNA gene sequence analysis indicated that the closest phylogenetic relatives were Thermoanaerobacter pseudethanolicus DSM2355T and T. brockii subsp. brockii DSM1457T, 98.3% and 98.0%, respectively. However, the strain BF1 was different with T. pseudethanolicus DSM2355T and T. brockii subsp. brockii DSM1457T in doubling time, optimum temperature and substrates utilized, and different with T. pseudethanolicus DSM 2355T in fatty acid profile. [Conclusion] The strain BF1 may be a new species of Thermoanaerobacter genus, the exact taxonomic status of it requires DNA hybridization further. The corrosion current density improved by its metabolic element sulfur may cause corrosion of oil pipelines and equipments.