| Located in the the Tarim River Valley of China, Natural Populus Euphratica Forest has been considered as the most concentrated, the best preserved and the most representative in the world. In this study,144 strains isolated from samples collected in surpace soil and lower soil of rhizosphere were primary identified. Based on phenotype, physiological and biochemical characteristics, and 16S rRNA gene sequences of 119 bacteria, the results show that bacterial population were obvious difference between in surpace soil and lower soil of rhizosphere. The bacteria isolated from surpace soil were belonged to Deinococcus-Thermus (56.5%), Actinobacteria (26.1%) and Proteobacteria (17.4%). And the latter were belonged to Firmicutes (45.6%), Actinobacteria (27.8%), Proteobacteria (11.4%) and Bacteroidetes (7.6%). The strains with drought-tolerant, few nutrients and radiation-resistant were preponderant groups in surpace soil. The strains show higher species richness with relative bacteria than surpace soil. It was found that 16S rRNA sequence similarities of 26 strains with relative bacteria were less than 97%, it suggest that the strains are potential new taxa.The similaritis of 16S rRNA gene sequences of two stains with their ralative species were less than 97%. Strain 7-15T, which was isolated from a soil sample collected from lower soil of rhizosphere in Populus Euphratica Forest, was a Gram-negative, aerobic, non-motile, rod-shaped bacterium. Colonies grown on 0.3×marine broth agar were circular, convex and pink-coloured. Its major cellular fatty acids were iso-C15:0(16.49%), iso-C17:03-OH (10.96%), C16:0 (9.11%), C18:0(7.87%) and Summed feature 4 (anteiso-C17:1B and/or iso-C1:1I,18.46%).The DNA G+C content of this strain was 44.9 mol% and MK-7 was the major respiratory quinone. Major polar lipids were diphosphatidylglycerol(DPG), phosphatidylglycerol(PG) and phosphatidylethanolamine(PE). In addition, two unknown phospholipids(PLs) and three unknown aminophospholipids(APLs) were also detected. The 16S rRNA gene sequence analysis indicated that strain 7-15T was related to the genus Pontibacter, with similarities ranging from 90.8 to 95.0%. On the basis of genotypic, phenotypic and phylogenetic data, strain 7-15T represents a novel species of the genus Pontibacter, for which the name Pontibacter populi sp. nov. is proposed, with 7-15T(=CCTCC AB 206239T=NRRL B-59488T) as type strain.Strains 7-26T Gram-negative, aerobic, non-motile and rod-shaped Pontibacter-like bacterium, was isolated also from the lower soil. Colonies grown on 0.3×marine broth agar were circular, convex and pink-coloured. Its major cellular fatty acids were iso-C15:0(15.90%), iso-C17:03-OH (9.45%), C16:0(4.82%), C18:0 (2.84%), iso-C16:0(6.09%), C17:1ω6c(5.29%), Summed Feature 4 (anteiso-C17:1B and/or iso-C17:1I, 21.04%). The DNA G+C content of this strain was 43.8 mol% and MK-7 was the major respiratory quinone. Major polar lipids were diphosphatidylglycerol(DPG), phosphatidylglycerol(PG) and phosphatidylethanolamine(PE). Five unknown phospholipids(PLs) and three unknown aminophospholipids(APLs) were also detected. Strains 7-26T displayed 16S rRNA gene sequence similarity to genus Pontibacter, and was in the different branch in phylogenetic tree. And similarities of strain 7-26T ranging from 93.9 to 96.4%. On the basis of genotypic, phenotypic and phylogenetic data, the strain represents a novel species of the genus Pontibacter, for which the name Pontibacter soil sp. nov. is proposed, with 7-26T(=CCTCC AB 206240T=NRRL B-59489T) as type strain.The strains obtained in this study laid a good foundation for farther reaserch of microbial diversity in Tarim natural Populus Euphratica Forest, and for development and application. The confirmed two new species also enriched the diversity of prokaryote. |
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