Thermoactinomyces guangxiensis sp. nov., a thermophilic actinomycete isolated from mushroom compost

A novel thermophilic actinomycete, designated strain CD-1T, was isolated from mushroom compost in Nanning, Guangxi province, China. The strain grew at 37–55 °C (optimum 45–50 °C), pH 6.0–11.0 (optimum pH 7.0–9.0) and with 0–2.0 % NaCl (optimum 0–1.0 %), formed well-developed white aerial mycelium and pale-yellow vegetative mycelium, and single endospores (0.8–1.0 μm diameter) were borne on long sporophores (2–3 μm length). The endospores were spherical-polyhedron in shape with smooth surface. Based on its phenotypic and phylogenetic characteristics, strain CD-1T is affiliated to the genus Thermoactinomyces. It contained meso-diaminopimelic acid as the diagnostic diamino acid; the whole-cell sugars were ribose and glucose. Major fatty acids were iso-C15 : 0, C16 : 0, anteiso-C15 : 0 and iso-C17 : 0. MK-7 was the predominant menaquinone. The polar phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylethanolamine containing hydroxylated fatty acids, ninhydrin-positive glycophospholipid, an unknown phospholipid and glycolipids. The G+C content of the genomic DNA was 48.8 %. 16S rRNA gene sequence analysis showed that the organism was closely related to Lihuaxuella thermophila YIM 77831T (95.69 % sequence similarity), Thermoactinomyces daqus H-18T (95.49 %), Laceyella putida KCTC 3666T (95.05 %), Thermoactinomyces vulgaris KCTC 9076T (95.01 %) and Thermoactinomyces intermedius JCM 3312T (94.55 %). Levels of DNA–DNA relatedness between strain CD-1T and Lihuaxuella thermophila JCM 18059T, Thermoactinomyces daqus DSM 45914T, Laceyella putida JCM 8091T, Thermoactinomyces vulgaris JCM 3162T and Thermoactinomyces intermedius JCM 3312T were low (22.8, 33.3, 24.7, 29.4 and 30.0 %, respectively). A battery of phenotypic, genotypic and DNA–DNA relatedness data indicated that strain CD-1T represented a novel species of the genus Thermoactinomyces, for which the name Thermoactinomyces guangxiensis sp. nov. is proposed. The type strain is CD-1T ( = ATCC BAA-2630T = CGMCC 4.7156T).