Novel thermophilic hydrolytic bacterium Rarispira pelagica gen. nov., sp. nov., reclassification of Spirochaeta thermophila as Winmispira thermophila gen. nov., comb. nov., and proposal of Winmispiraceae fam. nov. and Winmispirales ord. nov. in the class Spirochaetia

Abstract

A novel anaerobic moderately thermophilic bacterium, strain 38H-sp^T, was isolated from a hot spring located 12 m deep of the Kunashir Island shore. Gram-stain negative cells were non-sporeforming, motile, thin helices with regular coiling, occasionally forming bundles of cells. The strain grew at 30–60 °C and pH range of 5.5–8.4 with an optimum at 55 °C and pH 6.6–7.0. Strain 38H-sp^T required 0.5–5.5% NaCl (1.5% is an optimum) for growth. It was a chemoorganoheterotroph, growing on carbohydrates, including polymers (starch, pullulan, xylan, cellulose, arabinoxylan, xanthan gum, mannan, galactomannan, alginate and laminarin). Major products of glucose fermentation were acetate, ethanol, hydrogen, and carbon dioxide. Major cellular fatty acids were iso-C_15:0, C_14:0, C_12:1 DMA. The size of complete genome of strain 38H-sp^T was 2.35 Mb; DNA G + C content was 40.1%. 93 CAZymes including 54 glycoside hydrolases were found to be encoded in the genome of the strain. According to 16S rRNA gene sequence and conserved protein sequences phylogenies strain 38H-sp^T with its closest relative Spirochaeta thermophila represented a deeply branched lineage of the class Spirochaetia. Based on phylogenetic analysis and phenotypic features these two bacteria were assigned to a novel family within a novel order for that the names Winmispiraceae fam. nov. and Winmispirales ord. nov. are proposed with Winmispira thermophila gen. nov., comb. nov. (previously known as Spirochaeta thermophila) as type species. Strain 38H-sp^T (=DSM 100344^T = VKM B-2965^T) represents the novel genus and species Rarispira pelagica gen. nov., sp. nov.