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 JC227(T) was isolated from the gut of a wood-eating cockroach, Cryptocercus punctulatus (Scudder), from the Rann of Kutch, Gujarat, India. Strain JC227(T) was Gram-stain-negative, mesophilic, halotolerant and alkaliphilic. Based on 16S rRNA gene sequence analysis, strain JC227(T) belongs to the genus Spirochaeta, with Spirochaeta sphaeroplastigenens JC133(T) (99.51 %), S. odontotermitis JC202(T) (99.30 %), S. alkalica Z-7491(T) (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 JC227(T) and S. sphaeroplastigenens JC133(T), S. odontotermitis JC202(T), S. alkalica DSM 8900(T) and S. americana DSM 14872(T) was 62 +/- 2, 63, 58 +/- 2 and 48 +/- 4 %, respectively. Strain JC227(T) contained phosphatidylglycerol, diphosphatidylglycerol, an unidentified glycolipid and six unidentified lipids. Summed feature C-18 (: 1)omega 7c/C-18 : 1 omega 6c was the predominant cellular fatty acid, with significant proportions of C-16 : 0, C-14 : 0, C-12 : 0, C-15 : 1 omega 6c, C-16 : 1 omega 5c, C-16 : 1 omega 6c/C-16 : 1 omega 7c and C-17 : 0 2-OH. The DNA G+C content of strain JC227(T) was 55.5 mol%. On the basis of physiological, biochemical, chemotaxonomic (including metabolomic) and genomic differences from previously described taxa, strain JC227(T) 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 JC227(T) (=KCTC 15343(T) =NBRC 110105(T)). We also propose the reclassification of Spirochaeta sphaeroplastigenens, Spirochaeta odontotermitis, Spirochaeta alkalica and Spirochaeta americana as Alkalispirochaeta sphaeroplastigenens comb. nov. (type strain JC133(T) =KCTC 15220(T) =NBRC 109056(T)), Alkalispirochaeta odontotermitis comb. nov. (type strain JC202(T) =KCTC 15324(T) =NBRC 110104(T)), Alkalispirochaeta alkalica comb. nov. (type strain Z-7491(T) =DSM 8900(T) =ATCC 700262(T)) and Alkalispirochaeta americana comb. nov. (type strain ASpG1(T) =ATCC BAA-392(T) =DSM 14872(T)). The type species of Alkalispirochaeta gen. nov. is Alkalispirochaeta alkalica comb. nov.