Streptomyces marokkonensis sp. nov., isolated from rhizosphere soil of Argania spinosa L.

The novel actinomycete strain Ap1T was isolated from rhizosphere soil of the argan tree (Argania spinosa L.) in the south of Morocco. Strain Ap1T has been reported as a novel producer of the pentaene polyene macrolide isochainin, which strongly inhibits the growth of pathogenic yeasts and phytopathogenic fungi. Strain Ap1T shows a greyish-white aerial mycelium with chains of smooth-surfaced spores of the Spiralis type and a cell wall containing ll-diaminopimelic acid. Based on chemotaxonomy and morphological features, strain Ap1T was identified as a member of the genus Streptomyces. 16S rRNA gene sequence similarities based on almost-complete 16S rRNA gene sequences showed that strain Ap1T is closely associated with members of the Streptomyces violaceoruber species group (S. violaceoruber, S. coelescens, S. violaceorubidus, ‘S. caesius’, ‘S. lividans’, S. violaceolatus and S. humiferus) and others (Streptomyces aurantiogriseus, S. lienomycini, S. chattanoogensis, S. rubrogriseus and S. tendae). However, protein profiling, DNA–DNA hybridization and BOX-PCR fingerprinting proved a relationship above the species level. In addition, the phenotype also allowed for the differentiation of strain Ap1T from its closest neighbours. As a result of this polyphasic approach, we conclude that strain Ap1T represents a novel species of the genus Streptomyces, for which the name Streptomyces marokkonensis sp. nov. is proposed. The type strain is Ap1T (=R-22003T =LMG 23016T =DSM 41918T).