Description of Streptomyces explomaris sp. nov., isolated from the coastal soil rhizosphere of Juniperus excelsa and reclassification of Streptomyces libani as a later heterotypic synonym of Streptomyces nigrescens

The strain Je 1-4^T was isolated from the coastal rhizosphere soil of <i>Juniperus excelsa</i> M. Bieb. (Crimean Peninsula). Phylogenetic studies based on the 16S rRNA gene sequence revealed that Je 1-4^T is phylogenetically close to <i>Streptomyces libani</i> subsp. <i>libani</i> NBRC 13452^T (JCM 4322) and <i>Streptomyces nigrescens</i> NBRC 12894^T (DSM 40276) with sequence similarities of 99.86 to 99.93%. The genome of strain Je 1-4^T consisted of a linear chromosome with a size of 8.9 Mbp and a G+C content of 70.9mol%. Digital DNA-DNA hybridization (dDDH) analysis showed that Je 1-4^T is distinct from both <i>S. libani</i> subsp. <i>libani</i> and <i>S. nigrescens</i> (dDDH values of 66.6% and 66.7 %, respectively), while the latter two strains likely represent the same species (dDDH value of 92.0%). The predominant fatty acids in the strains were iso-C_16:0, anteiso-C_17:0 and anteiso-C_15:0, and the major menaquinones were MK9 H6 and MK9 H8. Based on these genomic and phenotypic data, strain Je 1-4^T represents a novel species of <i>Streptomyces</i>, for which the name <i>Streptomyces explomaris</i> sp. nov. is proposed. The type strain is Je 1-4^T (=DSM 117375^T=LMG 33490^T). Additionally, we propose that <i>S. libani</i> subsp. <i>libani</i> Baldacci and Grein 1966 (Approved Lists 1980) is a later heterotypic synonym of <i>S. nigrescens</i> (Sveshnikova 1957) Pridham et al. 1958 (Approved Lists 1980).