Five novel strains showing non-motile, alginolytic, halophilic and fermentative features were isolated from seawater samples off Okinawa in coral reef areas. These strains were characterized by an advanced polyphasic taxonomy including genome based taxonomy using multilocus sequence analysis (MLSA) and in silico DNA–DNA similarity (in silico DDH). Phylogenetic analyses on the basis of 16S rRNA gene sequences revealed that the isolates could be assigned to the genus Vibrio, however they were not allocated into any distinct cluster with known Vibrionaceae species. MLSA based on eight protein-coding genes (gapA, gyrB, ftsZ, mreB, pyrH, recA, rpoA, and topA) showed the vibrios formed an outskirt branch of Halioticoli clade. The experimental DNA–DNA hybridization data revealed that the five strains were in the range of being defined as conspecific but separate from nine Halioticoli clade species. The G + C contents of the Vibrio ishigakensis strains were 47.3–49.1 mol%. Both Amino Acid Identity and Average Nucleotide Identity of the strain C1T against Vibrio ezurae HDS1-1T, Vibrio gallicus HT2-1T, Vibrio halioticoli IAM 14596T, Vibrio neonatus HDD3-1T and Vibrio superstes G3-29T showed less than 95% similarity. The genome-based taxonomic approach by means of in silico DDH values also supports the V. ishigakensis strains being distinct from the other known Halioticoli clade species. Sixteen traits (growth temperature range, DNase and lipase production, indole production, and assimilation of 10 carbon compounds) distinguished these strains from Halioticoli clade species. The names V. ishigakensis sp. nov. is proposed for the species of Halioticoli clade, with C1T as the type strain (JCM 19231T = LMG 28703T).
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