Whole Genome Sequence of the Novel Marine Actinobacteria, <i>Streptomyces</i> sp. MMBL 11-3

Marine actinobacteria are valuable biological sources of various bioactive compounds, such as antibiotics, anticancer agents, and immunosuppressants [1].However, since the 2000s, identification of new species and antibiotics has been declining, coinciding with the increasing prevalence of multidrug resistance; therefore, these microorganisms are important for the identification of novel therapeutic agents [2].They also exhibit high biosynthetic potential; however, many biosynthetic gene clusters (BGCs) associated with secondary metabolite production are not expressed under standard laboratory conditions, limiting access to their chemical diversity [3].Therefore, genome sequencing and cryptic BGC identification are crucial for the discovery of new bioactive metabolites in these microorganisms [4].In this study, we aimed to isolate marine actinobacteria from marine sponges and conduct whole-genome sequencing to identify novel secondary metabolites.Additionally, we aimed to characterize their BGCs.We identified a novel marine actinobacteria, Streptomyces sp.MMBL 11-3, isolated from the deep-sea sponge, Spheciospongia panis.This sponge was collected from the Moon Island in Jeju, South Korea, with the assistance of the Korea Institute of Ocean Science & Technology.The harvested marine sponge was processed into a liquid sample via grinding and filtration.The liquid sample was overlaid on the ISP4 (BD DIFCO, USA), ISP2 (BD DIFCO, USA), and marine agar (BD DIFCO) media supplemented with 2% NaCl, 10 M nalidixic acid, and 20 M cycloheximide to selectively isolate actinobacteria, as previously described [5].Subsequently, Streptomyces sp.MMBL 11-3 was isolated from the colonies exhibiting characteristic actinobacterial morphology.The isolated strain was cultured in 500 ml of tryptic soy broth (BD DIFCO) at 28 for two days to extract the genomic DNA (gDNA) using the Wizard DNA Purification Kit (Promega, USA).The extracted gDNA was subjected to next-generation sequencing using the Illumina platform (for short reads) and PacBio Sequel System (for long reads; sequencing was performed by Macrogen, Marine actinobacteria are rich sources of bioactive compounds; however, many biosynthetic gene clusters (BGCs) are not expressed under standard conditions.In this study, we identified a novel actinobacterium, Streptomyces sp.MMBL 11-3, isolated from the deep-sea sponge, Spheciospongia panis, near Moon Island, Jeju, Republic of Korea.Whole-genome sequencing revealed a 9.5-Mb genome with 34 BGCs, including terpene, non-ribosomal peptide synthetase, polyketide synthase, and ribosomally synthesized and post-translationally modified peptide BGCs.Phylogenetic analysis confirmed its close relationship with other Streptomyces species.Therefore, Streptomyces sp.MMBL 11-3 can be used to identify novel secondary metabolites using genomic approaches in future studies.