Undibacter mobilis gen. nov., sp. nov. isolated from an artificial wetland in Okcheon, Korea

Strain GY_HT was isolated from an artificial wetland in Okcheon, Chungcheongbuk-do Province, Republic of Korea. Strain GY_HT was closely related to Pseudolabrys taiwanensis CC-BB4T based on 16S rRNA gene sequences (94.7 % similarity) and clustered within the family Nitrobacteraceae . Cells of the isolate were Gram-stain-negative, catalase-negative and oxidase-positive, and colonies were white or pale transparent. A flagellum was observed, and the isolate could respire both aerobically and anaerobically. Growth of GY_ HT was observed in the following conditions: 10–45 °C, pH 5–11 and 0–4 % NaCl. The optimal conditions for growth were 25 °C, pH 6.5–7.5 and 0.5–1.5 % NaCl. The major fatty acids were C19 : 0 cyclo ω8c (35.8 %) and summed feature 8 (C18 : 1  ω7c/C18 : 1  ω6c; 27.4 %). The major quinone was found to be ubiquinone-10. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine were the major polar lipids. The G+C content of the genome of GY_HT was 63.3 mol%. Based on its phylogenomic, physiological and biochemical attributes, strain GY_HT represents a novel species of a novel genus of the family Nitrobacteraceae . We propose the name as Undibacter mobilis gen. nov., sp. nov. The type strain is GY_HT (=KCTC 62792T=JCM 32856T).

Transfer of Sphingorhabdus marina, Sphingorhabdus litoris, Sphingorhabdus flavimaris and Sphingorhabdus pacifica corrig. into the novel genus Parasphingorhabdus gen. nov. and Sphingopyxis baekryungensis into the novel genus Novosphingopyxis gen. nov. within the family Sphingomonadaceae

During a phylogenetic analysis of Sphingorhabdus and its closely related genera in the family Sphingomonadaceae, we found that the genus Sphingorhabdus and the species Sphingopyxis baekryungensis might not be properly assigned in the taxonomy. Phylogenetic, phenotypic and chemotaxonomic characterizations clearly showed that the genus Sphingorhabdus should be reclassified into two genera (Clade I and Clade II), for which the original genus name, Sphingorhabdus, is proposed to be retained only for Clade I, and a new genus named as Parasphingorhabdus gen. nov. is proposed for Clade II with four new combinations: Parasphingorhabdus marina comb. nov., Parasphingorhabdus litoris comb. nov., Parasphingorhabdus flavimaris comb. nov. and Parasphingorhabdus pacifica comb. nov. Moreover, Sphingopyxis baekryungensis should represent a novel genus in the family Sphingomonadaceae, for which the name Novosphingopyxis gen. nov. is proposed, with a combination of Novosphingopyxis baekryungensis comb. nov. The study provides a new insight into the taxonomy of closely related genera in the family Sphingomonadaceae.

Sphingorhabdus soli sp. nov., isolated from Arctic soil

A Gram-stain-negative, strictly aerobic, rod-shaped and non-motile bacterial strain, designated D-2Q-5-6^T, was isolated from a soil sample collected from the Arctic region. Strain D-2Q-5-6^T was found to grow at 10-43 °C (optimum, 28 °C), at pH 6.0-9.0 (pH 7.0) and in 0-5 % (w/v) NaCl (0-1 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain D-2Q-5-6^T fell into the genus Sphingorhabdus and shared less than 95.8 % identity with all type strains of recognized species of this genus. The major cellular fatty acids of strain D-2Q-5-6^T were summed feature 8 (C_18 : 1 ω7c and/or C_18 : 1 ω6c; 31.4 %), summed feature 3 (C_16 : 1 ω7c and/or C_16 : 1 ω6c; 26.8 %) and C_14 : 0 2OH (11.7 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and sphingoglycolipid. The predominant quinone was identified as Q10. The DNA G+C content of strain D-2Q-5-6^T was 64.5 mol%. Based on the results of phylogenetic analysis and distinctive phenotypic characteristics, strain D-2Q-5-6^T is concluded to represent a novel species of the genus Sphingorhabdus, for which the name Sphingorhabdus soli sp. nov. is proposed. The type strain of the species is D-2Q-5-6^T (=MCCC 1A06070^T=KCTC 52311^T).

Sphingorhabdus lacus sp. nov. and Sphingorhabdus profundilacus sp. nov., isolated from freshwater environments

Two Gram-stain-negative, aerobic, non-motile bacteria, designated IMCC1753^T and IMCC26285^T, were isolated from a shallow eutrophic pond and a deep oligotrophic lake, respectively. Results of 16S rRNA gene sequence analysis indicated that the two strains shared 99.8 % sequence similarity and were most closely related to Sphingorhabdus contaminans JC216^T(98.7-98.8 %). The whole genome sequences of strains IMCC1753^T and IMCC26285^T were 3.5 and 2.9 Mbp in size with 56.6 and 55.5 mol% DNA G+C content, respectively. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains were 82.2 and 25.8 %, respectively, indicating that they are separate species. The two strains showed ≤98.8 % 16S rRNA gene sequence similarities and ≤82.2 % ANI and ≤28.7 % dDDH values to closely related species of the genus Sphingorhabdus, indicating that the two strains each represent novel species. Major fatty acid constituents of strain IMCC1753^T were C_17 : 1  ω6c, C_17 : 1  ω8c and summed features 3 (C_16 : 1  ω6c and/or C_16 : 1  ω7c) and 8 (C_18 : 1  ω6c and/or C_18 : 1  ω7c); those of strain IMCC26285^T were summed features 3 and 8. The predominant isoprenoid quinone detected in both strains was ubiquinone-10 and the most abundant polyamine was spermidine. Both strains contained phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol and sphingoglycolipid as major polar lipids. On the basis of the phylogenetic and phenotypic characteristics, strains IMCC1753^T and IMCC26285^T were considered to represent two distinct novel species in the genus Sphingorhabdus, for which the names Sphingorhabdus lacus (IMCC1753^T=KCTC 52480^T=KACC 18985^T=NBRC 112442^T) and Sphingorhabdus profundilacus (IMCC26285^T=KCTC 52479^T=KACC 18986^T=NBRC 112454^T) are proposed, respectively.