Mucilaginibacter aquatilis sp. nov., Mucilaginibacter arboris sp. nov., and Mucilaginibacter ginkgonis sp. nov., novel bacteria isolated from freshwater and tree bark

Three Gram-stain-negative, strictly aerobic, non-motile and rod-shaped bacterial strains, designated as HME9299^T, HMF7410^T and HMF7856^T, were isolated from freshwater and tree bark collected in Yong-in, Republic of Korea. Strains HME9299^T, HMF7410^T and HMF7856^T exhibited the highest 16S rRNA gene sequence similarities of 97.2, 94.4 and 96.4 % to Mucilaginibacter daejeonensis Jip 10^T, Mucilaginibacter terrae CCM 8645^T and Mucilaginibacter phyllosphaerae PP-F2F-G21^T, respectively. Among themselves, the values were 94.1-95.7 %. Phylogenetic analysis of the 16S rRNA gene sequences of the three isolates revealed that they belonged to the genus Mucilaginibacter within the family Sphingobacteriaceae. The predominant fatty acids of three strains were summed feature 3 (comprising C_16 : 1  ω7c and/or C_16 : 1  ω6c) and iso-C_15 : 0. Strain HME9299^T contained a relatively large amount of C_16 : 1  ω5c. The predominant respiratory quinone was menaquinone-7. The genome sizes of strains HME9299^T, HMF7410^T and HMF7856^T were 4.33, 4.16 and 3.68 Mbp, respectively, and their DNA G+C contents were 41.6, 38.4 and 43.9 mol%, respectively. Based on the results of the phenotypic, genotypic, chemotaxonomic and phylogenetic investigation, three novel species, Mucilaginibacter aquatilis sp. nov, Mucilaginibacter arboris sp. nov. and Mucilaginibacter ginkgonis sp. nov., are proposed. The type strains are HME9299^T (=KCTC 42122^T=DSM 29146^T), HMF7410^T (=KCTC 62464^T=NBRC 113227^T) and HMF7856^T (=KCTC 72782^T=NBRC 114275^T), respectively.

Chryseobacterium candidae sp. nov., isolated from a yeast (Candida tropicalis)

A Gram-stain-negative, rod shaped, non-motile, aerobic bacterium (strain JC507^T) was isolated from a yeast (Candida tropicalis JY101). Strain JC507^T was oxidase- and catalase-positive. Complete 16S rRNA gene sequence comparison data indicated that strain JC507^T was a member of the genus Chryseobacterium and was closely related to Chryseobacterium indologenes NBRC 14944^T (98.7 %), followed by Chryseobacterium arthrosphaerae CC-VM-7^T (98.6 %), Chryseobacterium gleum ATCC 35910^T (98.5 %) and less than 98.5 % to other species of the genus Chryseobacterium.The genomic DNA G+C content of strain JC507^T was 36.0 mol%. Strain JC507^T had phosphatidylethanolamine, four unidentified amino lipids and four unidentified lipids. MK-6 was the only respiratory quinone. The major fatty acids (>10 %) were anteiso-C_11 : 0, iso-C_15 : 0 and iso-C_17 : 03OH. The average nucleotide identity and in silico DNA-DNA hybridization values between strain JC507^T and C. indologenes NBRC 14944^T, C. arthrosphaerae CC-VM-7^T and C. gleum ATCC 35910^T were 80.2, 83.0 and 87.0 % and 24, 26.7 and 32.7 %, respectively. The results of phenotypic, phylogenetic and chemotaxonomic analyses support the inclusion of strain JC507^T as a representative of a new species of the genus Chryseobacterium, for which the name Chryseobacteriumcandidae sp. nov. is proposed. The type strain is JC507^T (=KCTC 52928^T=MCC 4072^T=NBRC 113872^T).

Phylogenetic insights into the diversity of Chryseobacterium species

The genus Chryseobacterium was formally established in 1994 and contains 112 species with validly published names. Most of these species are yellow or orange coloured, and contain a flexirubin-type pigment. The genomes of 83 of these 112 species have been sequenced in view of their importance in clinical microbiology and potential applications in biotechnology. The National Center for Biotechnology Information taxonomy browser lists 1415 strains as members of the genus Chryseobacterium, of which the genomes of 94 strains have been sequenced. In this study, by comparing the 16S rDNA and the deduced proteome sequences, at least 20 of these strains have been proposed to represent novel species of the genus Chryseobacterium. Furthermore, a yellow-coloured bacterium isolated from dry soil in the USA (and identified as Flavobacterium sp. strain B-14859) has also been reconciled as a novel member of the genus Chryseobacterium based on the analysis of 16S rDNA sequences and the presence of flexirubin. Yet another bacterium (isolated from a water sample collected in the Western Ghats of India and identified as Chryseobacterium sp. strain WG4) was also found to represent a novel species. These proposals need to be validated using polyphasic taxonomic approaches.