Croceibacterium gen. nov., with description of Croceibacterium ferulae sp. nov., an endophytic bacterium isolated from Ferula sinkiangensis K. M. Shen and reclassification of Porphyrobacter mercurialis as Croceibacterium mercuriale comb. nov.

A novel endophytic bacterium, designated strain SX2RGS8, was isolated from the surface-sterilized roots of an endangered medicinal plant (Ferula sinkiangensis K. M. Shen) collected from Xinjiang, north-western PR China. The taxonomic position of the candidate was investigated using a polyphasic approach. Strain SX2RGS8 was found to be aerobic, Gram-stain-negative, oxidase-negative, catalase-positive and axiolitic-shaped. Strain SX2RGS8 grew at 4-45 °C (optimum, 28 °C), pH 4.0-10.0 (pH 7.0) and in the presence of 0-5 % (w/v) NaCl. The polar lipids detected for strain SX2RGS8 were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, unidentified phosphoglycolipids, an unidentified phospholipid and unidentified lipids. The major respiratory quinone of strain SX2RGS8 was ubiquinone 10 and the major fatty acid was summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). The DNA G+C content was determined to be 66.5 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the isolate belonged to the family Erythrobacteraceae and showed 99.2 % (Porphyrobacter mercurialis), 95.5 % (Porphyrobacter donghaensisi) and 95.4 % (Porphyrobacter colymbi) similarities to its closest relatives. The isolate contained carotenoids, but no bacteriochlorophyll a. On the basis of phenotypic, genotypic and phylogenetic data, strain SX2RGS8 represents a novel species of a novel genus in the family Erythrobacteraceae, for which the name Croceibacterium ferulae gen. nov., sp. nov. is proposed. The type strain is SX2RGS8 (=CGMCC 1.16402=KCTC 62090). In addition, Porphyrobacter mercurialis Coil et al. 2016 is proposed to be transferred to this new genus as Croceibacterium mercuriale comb. nov.