Metagenome analysis of forty samples indicated a rich diversity of free living spirochaetes among Indian habitats. Only 2-3% of the total bacterial diversity was represented by spirochaetes with five distinct phylogenetic OTUs. A strain (JC230(T)) was brought to cultivation and its 16S rRNA gene sequence showed highest sequence similarity with that of Spirochaeta asiatica Z-7591(T) (90.78%). Genome sequence analysis of strain JC230(T) indicates the presence of 117 genes related to motility and chemotaxis. Strain JC230(T) is an obligate anaerobe. It is helical shaped, Gram-stain-negative and catalase and oxidase negative. Strain JC230(T) produces carotenoids and have all the genes related to carotenogenesis of spirilloxanthin series. Isoprenoid biosynthesis occurs through HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) pathway. Twelve bacterial haemoglobin and one flavohaemoglobin related genes are present in the genome of strain JC230(T). The genome of strain JC230(T) showed the presence of heavy metal resistance related genes of cobalt, zinc, cadmium and arsenic. Six genes related to colicin V and bacteriocin production cluster are present. Major (>2%) fatty acids were C12:0, C14:0, iso-C14:0, iso-C15:1H/C13:03OH, anteiso-C15:0, C16:0, and iso-C16:0. Strain JC230(T) contains diphosphatylglycerol, phosphatydilglycerol, phosphatydilethanolamine, unidentified phospholipid (PL1) and unidentified lipids (L1-7). G+C mol% of strain JC230(T) was 54.1%. Distinct morphological, physiological and genotypic differences from the previously described taxa support the classification of strain JC230(T) as a representative of a new species in the genus Spirochaeta, for which the name Spirochaeta lutea sp. nov. is proposed. The type strain is JC230(T) (=KCTC 15387(T)=DSM 29074(T)).
Keywords: Chemotaxonomic analysis; Spirochaeta lutea; Spirochaetes; Whole genome sequencing.
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