Phreatobacter yongcheonensis sp. nov., isolated from lava tube and emended description of the genus Phreatobacter

An aerobic, Gram-negative, catalase-positive, oxidase-positive bacterium, designated strain YC6-17T, was isolated from pieces of wood collected at the bottom of Youngcheon Cave in Jeju, Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YC6-17T formed a tight cluster with Phreatobacter oligotrophus DSM 25521T (98.07% sequence similarity) and distinctly separated from other taxa of the order Rhizobiales. Cells were motile rods and showed growth at 10-30 °C, pH 6-8 and 2% NaCl. Colonies were smooth, circular, convex and pale yellow in colour. The predominant ubiquinone was Q-10. The predominant fatty acids were C18:1ω7c, C16:0 and C18:0. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, two unknown glycolipids and an unknown lipid. The DNA G+C content was 64.4mol%. DNA-DNA relatedness between strain YC6-17T and the closest relative was 15.6±7.9%. Based on the combined data from phenotypic characterization and DNA-DNA hybridization as well as phylogenetic analysis, it was suggested that the isolate represents a novel species of the genus Phreatobacter, for which Phreatobacter yongcheonensis sp. nov. sp. nov. is proposed. The type strain is strain YC6-17T (= KCTC 52518T = DSM 103734T).

一株好氧、革兰氏阴性（Gram-negative）、过氧化氢酶阳性、氧化酶阳性的细菌，命名为菌株YC6-17^T，分离自韩国济州岛药泉洞（Youngcheon Cave）底部采集的木块样本。基于16S rRNA基因序列的系统发育分析显示，菌株YC6-17^T与贫营养潜穴杆菌（Phreatobacter oligotrophus）DSM 25521^T形成紧密聚类簇，序列相似性为98.07%，且与根瘤菌目（Rhizobiales）的其他类群明显区分。细胞为具运动性的杆状，可在10~30℃、pH 6~8及2%氯化钠条件下生长。菌落光滑、圆形、凸起，呈淡黄色。主要泛醌（ubiquinone）为Q-10，主要脂肪酸组分为C18:1ω7c、C16:0及C18:0。极性脂包括二磷脂酰甘油、磷脂酰乙醇胺、磷脂酰胆碱、两种未知糖脂及一种未知脂类。该菌株的DNA G+C含量为64.4mol%。菌株YC6-17^T与近缘模式菌株的DNA-DNA同源性为15.6±7.9%。综合表型特征鉴定、DNA-DNA杂交及系统发育分析的结果，表明该分离菌株属于潜穴杆菌属（Phreatobacter）的一个新物种，故提议将其命名为药泉潜穴杆菌（Phreatobacter yongcheonensis sp. nov.），其模式菌株为YC6-17^T（= KCTC 52518^T = DSM 103734^T）。