Abstract

The present study aimed to determine the taxonomic positions of strains designated R-5-52-3(T), R-5-33-5-1-2, R-5-48-2 and R-5-51-4 isolated from hot spring water samples. Cells of these strains were Gram-stain-negative, non-motile and rod-shaped. The strains shared highest 16S rRNA gene sequence similarity with Vulcaniibacterium thermophilum KCTC 32020(T) (95.1%). Growth occurred at 28-55 degrees C, at pH 6-8 and with up to 3% (w/v) NaCl. DNA fingerprinting, biochemical. phylogenetic and 16S rRNA, gene sequence analyses suggested that R-5-52-3(T), R-5-33-5-1-2, R-5-48-2 and R-5-51-4 were different strains but belonged to the same species. Hence, R-5-52-3(T) was chosen for further analysis and R-5-33-5-1-2, R-5-48-2 and R-5-51-4 were considered as additional strains of this species. R-5-52-3(T) possessed 0-8 as the only quinone and iso-C-15:0, iso-C-11:0. C-16:0 and iso-C-17:0 as major fatty acids. The polar lipids were diphosphatidylglycerol. phosphatidylglycerol, phosphatidylethanolamine, unidentified polar lipids and two unidentified phospholipids. The genomic G+C content was 71.6 mol%. Heat shock proteins (e.g. Hsp20, GroEL, Dna K and Clp ATPases) were noted in the R-5-52-3(T) genome, which could suggest its protection in the hot spring environment. Pan-genome analysis showed the number of singleton gene clusters among Vulcaniibacterium members varied. Average nucleotide identity (ANI) values between R-5-52-3(T), Vulcaniibacterium tengchongense YIM 77520(T) and V thermophilum KCTC 32020(T) were 80.1-85.8%, which were below the cut-off level (95-96%) recommended as the ANI criterion for interspecies identity. Thus, based on the above results. strain R-5-52-3(T) represents a novel species of the genus Vulcanfibacterium, for which the name Vulcaniibacterium gelatinicum sp. nov. is proposed. The type strain is R-5-52-3(T) (=KCTC 7206(T)=CGMCC 1.16678(T)).