Abstract

A Gram-negative, non-motile, aerobic, and rod-shaped bacterial strain designated as BR5-28T was isolated from the soil of a ginseng field at Baekdu Mountain Korea, and its taxonomic position was investigated using a polyphasic approach. Strain BR5-28T grew at 10–42°C (optimum temperature, 30°C) and pH 5.5–8.5 (optimum pH, 7.0) on R2A agar medium without additional NaCl supplementation. Strain BR5- 28T exhibited β-glucosidase activity, which was responsible for its ability to transform the ginsenosides Rb1 and Rd (the two dominant active components of ginseng) to compound-K. Based on 16S rRNA gene phylogeny, the novel strain showed a new branch within the genus Mucilaginibacter of the family Sphingobacteriaceae, and formed clusters with Mucilaginibacter frigoritolerans FT22T (95.8%) and Mucilaginibacter gotjawali SA3-7T (95.7%). The G+C content of the genomic DNA was 45.1%. The predominant respiratory quinone was MK-7 and the major fatty acids were summed feature 3 (comprising C16:1 ω6c and/or C16:1 ω7c), iso-C15:0 and anteiso-C15:0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Strain BR5- 28T was differentiated genotypically and phenotypically from the recognized species of the genus Mucilaginibacter. The isolate therefore represents a novel species, for which the name Mucilaginibacter hankyongensis sp. nov. is proposed, with the type strain BR5-28T (=KCTC 22274T =DSM 21151T).

• Keywords: 16S rRNA gene; polyphasic taxonomy; Mucilaginibacter hankyongensis; ginsenoside