Alkalispirochaeta cellulosivorans gen. nov., sp. nov., a cellulose-hydrolysing, alkaliphilic, halotolerant bacterium isolated from the gut of a wood-eating cockroach (Cryptocercus punctulatus), and reclassification of four species of Spirochaeta as new combinations within Alkalispirochaeta gen. nov.

An obligately anaerobic spirochaete designated strain JC227T was isolated from the gut of a wood-eating cockroach, Cryptocercus punctulatus (Scudder), from the Rann of Kutch, Gujarat, India. Strain JC227T was Gram-stain-negative, mesophilic, halotolerant and alkaliphilic. Based on 16S rRNA gene sequence analysis, strain JC227T belongs to the genus Spirochaeta, with Spirochaeta sphaeroplastigenens JC133T (99.51%), S. odontotermitis JC202T (99.30%), S. alkalica Z-7491T (99.10%), S. americana (98.54%) and other members of the genus Spirochaeta (<92.7%) as its closest phylogenetic neighbours. However, DNA-DNA hybridization between strain JC227T and S. sphaeroplastigenens JC133T, S. odontotermitis JC202T, S. alkalica DSM 8900T and S. americana DSM 14872T was 62±2, 63, 58±2 and 48±4 %, respectively. Strain JC227T contained phosphatidylglycerol, diphosphatidylglycerol, an unidentified glycolipid and six unidentified lipids. Summed feature C18:1ω7c/C18:1ω6c was the predominant cellular fatty acid, with significant proportions of C16:0, C14:0, C12:0, C15:1ω6c, C16:1ω5c, C16:1ω6c/C16:1ω7c and C17:0 2-OH. The DNA G+C content of strain JC227T was 55.5 mol%. On the basis of physiological, biochemical, chemotaxonomic (including metabolomic) and genomic differences from previously described taxa, strain JC227T can be differentiated from members of the genus Spirochaeta and represents a novel species of a new genus, for which the name Alkalispirochaeta cellulosivorans gen. nov., sp. nov. is proposed. The type strain of Alkalispirochaeta cellulosivorans is JC227T (=KCTC 15343T=NBRC 110105T). We also propose the reclassification of Spirochaeta sphaeroplastigenens, Spirochaeta odontotermitis, Spirochaeta alkalica and Spirochaeta americana as Alkalispirochaeta sphaeroplastigenens comb. nov. (type strain JC133T=KCTC 15220T=NBRC 109056T), Alkalispirochaeta odontotermitis comb. nov. (type strain JC202T=KCTC 15324T=NBRC 110104T), Alkalispirochaeta alkalica comb. nov. (type strain Z-7491T=DSM 8900T=ATCC 700262T) and Alkalispirochaeta americana comb. nov. (type strain ASpG1T=ATCC BAA-392T=DSM 14872T). The type species of Alkalispirochaeta gen. nov. is Alkalispirochaeta alkalica comb. nov.