Tepidiphilus olei sp. nov., isolated from the production water of a water-flooded oil reservoir in PR China.

A novel, moderately thermophilic, Gram-stain-negative bacterium, designated strain J18T, was isolated from a water-flooded oil reservoir. Cells were aerobic, oxidase- and catalase-positive, with a polar flagellum. Growth occurred at 35-60 °C and at pH 6-8.5. The respiratory quinones were ubiquinone 8 and ubiquinone 9. The dominant cellular fatty acids were C16 : 0, C17 : 0 cyclo, C19 : 0 cyclo ω8c and summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c). The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid, an unidentified phospholipid and an unidentified aminophospholipid. The strain showed the highest 16S rRNA gene sequence similarities to Tepidiphilus margaritifer DSM 15129T (98.6 %), Tepidiphilus succinatimandens DSM 15512T (98.4 %) and Tepidiphilus thermophilus DSM 27220T (98.1 %), respectively, and the similarity to other species was lower than 93 %. In the phylogenetic trees, it constituted a unique sub-cluster within the genus Tepidiphilus. The DNA G+C content of strain J18T was 64.44 mol%. As compared with the type strains, the genome-to-genome distances of strain J18T were 34.7-40 %. These results confirmed the separate species status of J18T with its close relatives. On the basis of physiological, chemotaxonomic and phylogenetic analyses along with the low levels of identity at the whole-genome level, it can be concluded that strain J18T represents a new species of the genus Tepidiphilus, for which the name Tepidiphilus olei sp. nov. is proposed. The type strain of T. olei is J18T (=CGMCC 1.16800T=LMG 31400T).

[Effect of N2O produced by indigenous denitrifiers in oil reservoir on the physical properties of crude oil]. / 油藏本源反硝化功能菌的产气作用(N2O)及对原油物性的影响.

The success of microbial enhanced oil recovery (MEOR) relies on complex microbial processes. Nevertheless, the contribution and mechanism of in-situ denitrification to microbial oil recovery remain unclear. In this study, eight denitrifying bacterial strains, designated T1, D1, D44, D46, D15, S1, S2 and S6, were isolated from the produced water of Xinjiang Oilfield, China, by a double layered plate method. The16S rDNA gene sequences of these denitrifying strains shared 100% similarity with Pseudomonas stutzeri (T1, D1, and D44), Pseudomonas putida (D46 and D15), and Pseudomonas aeruginosa (S1, S2, S6), respectively. The N2O production effects of these strains on the physical properties of crude oil were evaluated with batch experiment. Results showed that the highest total gas yield was observed with sucrose as carbon source, and the maximal concentration of N2O occurred with glycerol as carbon source. The denitrification process by these bacterial strains led to volume expansion and viscosity reduction of crude oil. Crude oil expansion rate was positively correlated with the concentration of N2O, with a correlation coefficient of 0.983, but not correlated with the volume of total gas production. Strain S1, S2, and S6 produced 530-730 mg·L-1 of surfactant using glycerol as ole carbon source, which could reduce surface tension and emulsify crude oil. However, these surfactant-producing strains produced less N2O, exhibited weaker effects on oil swelling and viscosity reduction, compared to the none-surfactant-producing denitrifying strains. Our results suggested that more attention should be paid to the ability of N2O production by denitrifying bacteria when exploiting microbial resources towards enhancing oil recovery.