Genome sequencing and comparative analysis of Nocardiopsis moroccensis sp. nov., a halotolerant Actinomycetota from Moroccan hypersaline ecosystem

Abstract

Saline and arid ecosystems are recognized as promising reservoirs of novel Actinomycetota with unique adaptations and secondary metabolic potential. In this study, a halotolerant Actinomycetota strain, designated ZS3416R2A, was isolated from saline soil in the hypersaline wetland of Lake Zima, Morocco. Phylogenetic analysis based on the 16S rRNA gene sequence showed 99.03% similarity to Nocardiopsis terrae DSM 45157 T, indicating close affiliation with the genus Nocardiopsis. Whole-genome sequencing revealed a 6.1 Mb circular chromosome with a G + C content of 70.48% and 5,855 coding sequences. Genome-based metrics (ANI 95.07%, dDDH 66.4%) supported its classification as a novel species distinct from N. terrae, while AAI (95.87%) and POCP (82.4%) confirmed its placement within the genus. Comparative analyses revealed unique gene families, biosynthetic gene clusters, and regions of genomic plasticity in strain ZS3416R2A. Phenotypically, strain ZS3416R2A grew over a broad range of salinity (0–10%), temperature (16–37 °C), and pH (7.0–8.0), and formed denser aerial mycelia than strain DSM 45157 T, reflecting adaptation to the arid saline environment of Lake Zima. Chemotaxonomic characterization identified MK-10(H6), MK-10(H4) and MK-9(H4) as predominant menaquinones, iso-C16:0 and 10-methyl-C18:0 as major fatty acids, and diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, and phosphatidylinositol as major polar lipids. Based on this polyphasic evidence, strain ZS3416R2A represents a novel species within the genus Nocardiopsis, for which the name Nocardiopsis moroccensis sp. nov. is proposed. The type strain is ZS3416R2AT (= CCMM B1332T = DSM 120542 T).