Saccharopolyspora subtropica sp. nov., a thermophilic actinomycete isolated from soil of a sugar cane field

A novel thermophilic actinomycete, designated strain T3T, was isolated from a soil sample of a sugar cane field. The strain grew at 25-60 °C (optimum 37-50 °C), at pH 6.0-11.0 (optimum 7.0-9.0) and with 0-12.0 % (w/v) NaCl (optimum 0-7 %). The aerial mycelium was white and the vegetative mycelium was colourless to pale yellow. The substrate mycelium fragmented into rod-shaped elements after 4-5 days at 50 °C. The aerial mycelium formed flexuous chains of 5-20 spores per chain; the oval-shaped spores had spiny surfaces and were non-motile. The organism contained meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The whole-cell sugars consisted of arabinose, galactose and ribose. The cellular fatty acid profile consisted mainly of anteiso-C17 : 0, iso-C17 : 0 and iso-C16 : 0. The quinone system was composed predominantly of MK-9(H4). The phospholipids detected were diphosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylmethylethanolamine and ninhydrin-positive glycophospholipids. The DNA G+C content of strain T3T was 71.3 mol%. The organism showed a combination of morphological and chemotaxonomic properties typical of members of the genus Saccharopolyspora. In the 16S rRNA gene tree of Saccharopolyspora it formed a distinct phyletic line and was related most closely to Saccharopolyspora thermophila 216T. However, the phenotypic characteristics of strain T3T were significantly different from those of S. thermophila 216T and DNA-DNA hybridization revealed a low level of relatedness (28.6-32.3 %) between them. Based on the phenotypic and phylogenetic data, strain T3T represents a novel species in the genus Saccharopolyspora, for which the name Saccharopolyspora subtropica sp. nov. is proposed. The type strain is T3T ( = DSM 46801T = CGMCC 4.7206T).