Thermoactinomyces daqus sp. nov., a thermophilic bacterium isolated from high-temperature Daqu.

Daqu is a fermentation starter used in the production of Chinese liquors. A thermophilic bacterium, designated strain H-18(T), was isolated from a high-temperature Daqu sample collected from the manufacturing process of a sesame-flavoured liquor in Shandong province, China. It was investigated in a taxonomic study using a polyphasic approach. Strain H-18(T) formed white aerial mycelium and greyish-yellow substrate mycelium, bearing single endospores on aerial and substrate hyphae or on unbranched short sporophores. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The major fatty acids were iso-C15 : 0 and iso-C17 : 0. The predominant menaquinone was MK-7. These chemotaxonomic properties are similar to those of members of the genus Thermoactinomyces. The G+C content of the genomic DNA was 49.1 mol%. 16S rRNA gene sequence comparisons indicated that strain H-18(T) was most closely related to Thermoactinomyces vulgaris KCTC 9076(T) (96.42 % similarity), Thermoactinomyces intermedius KCTC 9646(T) (96.06 %), Laceyella putida KCTC 3666(T) (96.32 %) and Laceyella sacchari KCTC 9790(T) (95.55 %). Strain H-18(T) showed low DNA-DNA relatedness (40.8, 33.4, 20.0 and 14.4 %) with the above strains. Based on morphological and chemotaxonomic characteristics, DNA-DNA hybridization data and physiological properties, strain H-18(T) represents a novel species of the genus Thermoactinomyces, for which the name Thermoactinomyces daqus sp. nov. is proposed. The type strain is H-18(T) ( = DSM 45914(T) = CICC 10681(T)).