Polyphasic and genomic characterisation of Streptomyces zimensis sp. nov., a halotolerant Actinomycetota from the Saline Lake Zima in Morocco

Abstract

Members of the phylum Actinomycetota are widely distributed across diverse environments and are well known for their metabolic versatility and capacity to produce bioactive compounds. In this study, strain ZE1316R2Aᵀ was isolated from the saline water collected from Lake Zima (Morocco) and subjected to comprehensive polyphasic taxonomic characterisation. Phylogenetic analysis based on the 16 S rRNA gene placed strain ZE1316R2Aᵀ within the genus Streptomyces , showing highest sequence similarity with S. albidoflavus DSM 40,455 T (99.71%). However, genome-based indices, including average nucleotide identity (ANIb = 94.84%, ANIm = 96.09%) and digital DNA-DNA hybridization (dDDH = 64.9%), supported its distinction as a separate species. The draft genome (7.41 Mb; G + C = 73.26 mol%) comprises 6,464 coding sequences and reveals the presence of strain-specific genomic regions and biosynthetic gene clusters. Comparative analyses highlighted both a conserved core genome and a substantial accessory genome component, reflecting genomic differentiation relative to closely related taxa. Phenotypic and chemotaxonomic characteristics were consistent with assignment to the genus Streptomyces , while supporting its differentiation at the species level. Based on the combined genomic, phenotypic, and chemotaxonomic evidence, strain ZE1316R2Aᵀ represents a novel species of the genus Streptomyces , for which the name Streptomyces zimensis sp. nov., is proposed. This study expands current knowledge of Streptomyces diversity associated with saline environments and highlights the genomic diversity present within closely related taxa. The type strain is ZE1316R2Aᵀ (= CCMM B1331 T  = DSM 120541 T ).