Spirosoma utsteinense sp. nov. isolated from Antarctic ice-free soils from the Utsteinen region, East Antarctica

Between 2014 and 2016, 16 Gram-stain-negative, aerobic, rod-shaped and yellow-orange pigmented bacteria were isolated from exposed soils from the Utsteinen region, Sor Rondane Mountains, East Antarctica. Analysis of their 16S rRNA gene sequences revealed that the strains form a separate cluster in the genus Spirosoma, with Spirosoma rigui KCTC 12531(T) as its closest neighbour (97.8 % sequence similarity). Comparative genome analysis of two representative strains (i.e. R-68523(T) and R-68079) of the new group with the type strains of Spirosoma rigui (its closest neighbour) and Spirosoma linguale (type species of the genus), yielded average nucleotide identity values of 73.9-78.7%. Digital DNA-DNA reassociation values of the two strains and these type strains ranged from 20.3 to 22.0%. The predominant cellular fatty acids of the two novel strains were summed feature 3 (i.e. C-16:1 omega 7c and/or iso-C-15 2-OH), C-16:1 omega 5c, C-16:0 and iso-C-15:0. The new Spirosoma strains grew with 0-0.5 % (w/v) NaCl, at pH 6.5-8.0 and displayed optimum growth between 15 and 25 degrees C. Based on the results of phenotypic, genomic, phylogenetic and chemotaxonomic analyses, the new strains represent a novel species of the genus Spirosoma for which the name Spirosoma utsteinense sp. nov. is proposed. The type strain is R-68523(T) (=LMG 31447(T)=CECT 9925(T)).