DNA-DNA relatedness among Thermoactinomyces species: Thermoactinomyces candidus as a synonym of Thermoactinomyces vulgaris and Thermoactinomyces thalpophilus as a synonym of Thermoactinomyces sacchari

DNA-DNA relatedness of all validly described Thermoactinomyces species was determined to infer the genetic relationships between them. The levels of D NA-DNA relatedness among the type strains of Thermoactinomyces species rang ed from 2.5 to 92.8%. Based on DNA relatedness data, the type strains of Th ermoactinomyces intermedius, Thermoactinomyces putidus, Thermoactinomyces d ichotomicus and Thermoactinomyces peptonophilus were considered to be disti nct species of the genus Thermoactinomyces. However, the relationship betwe en the type strains of Thermoactinomyces vulgaris and Thermoactinomyces can didus and the relationship between the type strains of Thermoactinomyces sa cchari and Thermoactinomyces thalpophilus were reevaluated from levels of D NA-DNA relatedness. The independent DNA relatedness values between Thermoac tinomyces vulgaris KCTC 9076(T) and Thermoactinomyces candidus KCTC 9557(T) were 90.8 and 92.8 %, Thermoactinomyces thalpophilus KCTC 9789(T) and Ther moactinomyces sacchari KCTC 9790(T) exhibited independent values of 85.6 an d 87.3 %. Accordingly, on the basis of DNA-DNA relatedness data together wi th 16S rDNA sequence data determined recently, it is proposed that Thermoac tinomyces candidus should be considered as a synonym of Thermoactinomyces v ulgaris and Thermoactinomyces thalpophilus be considered as a synonym of Th ermoactinomyces sacchari.