Description of Venenivibrio orakeikorakoensis sp. nov. and Venenivibrio aotearoaensis sp. nov, and emended description of genus Venenivibrio, Venenivibrio stagnispumantis species

Two thermophilic bacterial strains, designated OKO1 and KUI1, were isolated from hot springs within the Taup[o] Volcanic Zone of New Zealand. Analysis of the 16S rRNA gene identified both as members of the genus Venenivibrio, sharing 99.13% and 98.82% sequence similarity with Venenivibrio stagnispumantis CP.B2T, respectively. The novel isolates were characterised using a polyphasic taxonomic approach alongside V. stagnispumantis. Despite their close phylogenetic relationship, the strains differed markedly in cell morphology, physiology and genomic content. Both isolates exhibited broad tolerance to temperature and pH, while re-examination V. stagnispumantis CP.B2T revealed substantially wider physiological capabilities than previously reported, bringing its phenotype into closer agreement with the new isolates. Comparative genomic analyses identified key differences in genes encoding cytochromes, hydrogenases, and nitrogen metabolism, suggesting distinct metabolic potential among the strains. Although the genomes shared average nucleotide identity (ANI) values of 95-96%, placing them near the accepted species boundary, the combined phenotypic and genomic evidence support recognition of OKO1T and KUI1T as two species within the genus. We therefore propose Venenivibrio orakeikorakoensis sp. nov. (type strain OKO1T, ACCESSION) and Venenivibrio aotearoaensis sp. nov. (type strain KUI1T, ACCESSION) as new members within the genus, and emend the descriptions of Venenivibrio stagnispumantis and the genus Venenivibrio to incorporate the expanded phenotypic and genomic diversity revealed in this study.