Sinorhodobacter populi sp. nov., isolated from the symptomatic bark tissue of Populus × euramericana canker

Sedimentimonas flavescens gen. nov., sp. nov., isolated from sediment of Clam Island, Liaoning Province

A novel Gram-stain negative, aerobic and ovoid to short rod shaped bacterium with a single polar flagellum, named strain B57^T, was isolated from sediment of Clam Island, Liaoning Province, China. The optimal growth of this strain was found to occur at 37 °C, pH 6-6.5, and in the presence of 2% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain B57^T forms a distinct lineage within the family Rhodobacteraceae, sharing high 16S rRNA gene sequence similarity with Sinirhodobacter populi sk2b1^T (97.4%). The average amino acid identity of B57^T and the closely related species were lower than the threshold level for genus delineation. The dominant respiratory quinone of strain B57^T was identified as Q-10. The major fatty acids were found to be Summed Feature 8 (C_18:1ω7c and/or C_18:1ω6c), Summed Feature 3 (C_16:1ω7c and/or C_16:1ω6c) and C_16: 0. The polar lipids were identified as phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, two unidentified phospholipids, one unidentified glycolipid, and one unidentified lipid. The DNA G + C content of strain B57^T was determined to be 64.1 mol%. Based on the biochemical, phylogenetic and chemotaxonomic analysis, strain B57^T is concluded to represent a novel species of a novel genus, for which the name Sedimentimonas flavescens gen. nov., sp. nov.is proposed. The type strain is B57^T (= CGMCC1.19488^T = KCTC 92053^T).

Degradation of 1,4-Dioxane by Xanthobacter sp. YN2

1,4-Dioxane is a highly toxic and carcinogenic pollutant found worldwide in groundwater and soil environments. Several microorganisms have been isolated by their ability to grow on 1,4-dioxane; however, low 1,4-dioxane tolerance and slow degradation kinetics remain obstacles for their use in 1,4-dioxane bioremediation. We report here the isolation and characterization of a new strain, Xanthobacter sp. YN2, capable of highly efficient 1,4-dioxane degradation. High degradation efficiency and high tolerance to 1,4-dioxane make this new strain an ideal candidate for the biodegradation of 1,4-dioxane in various treatment facilities. The maximum degradation rate of 1,4-dioxane was found to be 1.10 mg-1,4-dioxane/h mg-protein. Furthermore, Xanthobacter sp. YN2 was shown to grow in the presence of higher than 3000 mg/L 1,4-dioxane with little to no degradation inhibition. In addition, Xanthobacter sp. YN2 could grow on and degrade 1,4-dioxane at pH ranges 5 to 8 and temperatures between 20 and 40 °C. Xanthobacter sp. YN2 was also found to be able to grow on a variety of other substrates including several analogs of 1,4-dioxane. Genome sequence analyses revealed the presence of two soluble di-iron monooxygenase (SDIMO) gene clusters, and regulation studies determined that all of the genes in these two clusters were upregulated in the presence of 1,4-dioxane. This study provides insights into the bacterial stress response and the highly efficient biodegradation of 1,4-dioxane as well as the identification of a novel Group-2 SDIMO.

Sinirhodobacter hankyongi sp. nov., a novel denitrifying bacterium isolated from sludge

A novel Gram-reaction-negative, facultative-aerobic, motile, non-spore-forming, oval-shaped and denitrifying bacterium, designated BO-81^T, was isolated from sludge sampled in the Republic of Korea. This bacterium was investigated via a polyphasic approach to reveal its taxonomic position. The results of phylogenetic analysis based on 16S rRNA gene sequencing indicated that strain BO-81^T belonged to the family Rhodobacteraceae and was related to the closest species Sinirhodobacter ferrireducens (98.8 % sequence similarity), 'Sinorhodobacter hungdaonensis' (98.4 %), Rhodobacter lacus (97.8 %), Sinorhodobacter populi (96.8 %) and Rhodobacter maris (96.2 %). The average nucleotide identity and DNA-DNA hybridization values between strain BO-81^T and its closely related strains were 77.7-94.2 % and 20.1-55.9 %, respectively, indicating that BO-81^T represents a novel species of the genus Sinirhodobacter. Growth occurred at 18-40 °C on Reasoner's 2A medium in the presence of 0-7 % NaCl (w/v) and at pH 6.0-9.0. Strain BO-81^T was characterized chemotaxonomically as having ubiquinone 10 as its predominant respiratory quinone, summed feature 8 (C_18 : 1 ω6c and/or C_18 : 1 ω7c) as its major fatty acid and phosphatidylglycerol and phosphatidylethanolamine as its predominant polar lipids. The G+C content of the genomic DNA was 68.3 mol%. The results of physiological and biochemical tests allowed phenotypic differentiation of strain BO-81^T from other Sinirhodobacter species with validly published names. Therefore, the isolate represented a novel species, for which the name Sinirhodobacter hankyongi sp. nov. (type strain BO-81^T=KACC 19677^T=LMG 30808^T) is proposed.

Solirhodobacter olei gen. nov., sp. nov., a nonphotosynthetic bacterium isolated from oil-contaminated soil

A nonphotosynthetic, Gram-stain-negative, rod-shaped and motile strain, designated Pet-1^T, was isolated from oil-contaminated soil collected from Daqing oil field in China. Optimal growth occurred at 37 °C, pH 5.5 and in 1 % (w/v) NaCl. Q-10 was the sole respiratory quinone. The most abundant fatty acid was C_{18 : 1}ɷ7c/C_{18 : 1}ɷ6c (67.4 %). The major polar lipids were phosphatidylglycerol, aminolipid, phosphatidylethanolaine, phosphatidycholine, two unidentified lipids and two unidentified phospholipids. The genomic DNA G+C content was 69.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that Pet-1^T shared the highest similarity (95.1 %) to Rhodobacter vinaykumarii DSM 18714^T, followed by Sinorhodobacter populi sk2b1^T (95.0 %) and Haematobacter massiliensis CCUG 47968^T (95.0 %). In the phylogenetic tree, strain Pet-1^T formed a separate branch from the closely related genera Rhodobacter, Pararhodobacter, Defluviimonas and Rhodovulum within the family Rhodobacteraceae. Based on the data from the current polyphasic study, it is proposed that the isolate is a novel species of a novel genus within the family Rhodobacteraceae, with the name Solirhodobacter olei gen. nov., sp. nov. The type strain of the type species is Pet-1^T (=KCTC 72074^T =CCTCC AB 2018368^T).