Three strains of Streptomyces reticuliscabiei and two strains of Streptomyces turgidiscabies were analysed, together with reference and type strains of other Streptomyces species, for phenotypic traits, DNA–DNA relatedness, comparison of 16S rRNA gene sequences and presence of necrotic protein gene (nec1) homologues in order to clarify their phylogenetic relationships. A numerical analysis of phenotypic characteristics showed that S. reticuliscabiei and S. turgidiscabies belong to the same cluster and share almost all morphological and biochemical traits that are important in the identification of Streptomyces species. DNA–DNA hybridization and phylogenetic comparisons of 16S rRNA gene sequences confirmed that the two species are genomically closely related. In contrast, pathological data showed that S. turgidiscabies and S. reticuliscabiei cause two distinct diseases. Gene homologues of nec1 were detected in S. turgidiscabies and other common scab species (Streptomyces scabiei, Streptomyces europaeiscabiei and Streptomyces stelliscabiei), but not in S. reticuliscabiei. To avoid confusion between agents causing separate diseases, it is proposed that the existing distinct species names are retained: S. turgidiscabies involved in common scab and S. reticuliscabiei involved in netted scab.
A Gram-positive, non-motile, rod- or coccoid-shaped Isoptericola-like bacterium, strain DS-3T, was isolated from a soil sample from Dokdo, Korea, and its taxonomic position was investigated by a polyphasic approach. The organism grew optimally at 30 °C and pH 7.0–8.0. Strain DS-3T had the peptidoglycan type based on l-lys–d-Asp, and galactose, glucose, rhamnose and ribose as the whole-cell sugars. It contained MK-9(H4) as the predominant menaquinone and anteiso-C15 : 0 and iso-C15 : 0 as the major fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two unidentified glycolipids. The DNA G+C content was 74.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain DS-3T was most closely related to members of the genus Isoptericola. Similarity values between the 16S rRNA gene sequences of strain DS-3T and the type strains of Isoptericola species ranged from 98.0 to 98.4 %. DNA–DNA relatedness values (11–23 %) and differential phenotypic properties demonstrated that strain DS-3T was distinguishable from recognized Isoptericola species. On the basis of phenotypic properties and phylogenetic and genetic distinctiveness, strain DS-3T represents a novel species in the genus Isoptericola, for which the name Isoptericola dokdonensis sp. nov. is proposed. The type strain is DS-3T (=KCTC 19128T=CIP 108921T).