A novel thermophilic filamentous bacterium, designated strain T36(T), was isolated from soil sediment sample from a hot spring source collected in Khenchela province, Algeria. Strain T36(T) was identified as a member of the genus Thermoactinomyces by a polyphasic approach. Strain T36(T) was observed to form white aerial mycelium and non-coloured to pale yellow substrate mycelium, both producing endospores, sessile or borne by short sporophores. The optimum growth temperature and pH were found to be 37-55 °C and 7.0-9.0, respectively and the optimum NaCl concentration for growth was found to be 0-7 % (w/v). The diagnostic diamino acid in the cell wall peptidoglycan was identified as meso-diaminopimelic acid. The predominant menaquinone of strain T36(T) was identified as MK-7 (H0). The major fatty acids were found to be iso-C15:0 and iso-C17:0. The phospholipids detected were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphoglycolipid. The chemotaxonomic properties of strain T36(T) are consistent with those shared by members of the genus Thermoactinomyces. 16S rRNA gene sequence analysis indicated that the sequence similarities between strain T36(T) and Thermoactinomyces species with validly published names were less than 98 %. Based on the combined genotypic and phenotypic evidence, it is proposed that strain T36(T) should be classified as representative of a novel species, for which the name Thermoactinomyces khenchelensis sp. nov. is proposed. The type strain is T36(T) (=DSM 45951(T) = CECT 8579(T)).
Keywords: Hot spring; Polyphasic taxonomy; Thermoactinomyces; Thermoactinomyces khenchelensis sp. nov.; Thermophilic filamentous bacterium.