Mangrove soil-derived Streptomyces viridiostaticus as a source of dual therapeutic bioactives: antimicrobial proteins and Tryprostatin B alkaloid with anticancer potency.

[BACKGROUND] Actinomycetes are prolific producers of secondary metabolites with strong antimicrobial and anticancer potential. Mangrove ecosystems remain underexplored yet are rich sources of novel bioactive actinomycetes. This study aimed to characterize and evaluate the therapeutic bioactivities of Streptomyces viridiostaticus isolated from mangrove soil of the Mangalore coastal region, India.

[METHODS] The isolate was culturally and biochemically evaluated using starch casein nitrate agar (SCNA) and selective media. Antibacterial activity of crude extract was evaluated against Gram-positive and Gram-negative clinical pathogens. Protein purification was achieved via Sephadex G-10 size-exclusion chromatography. Cytotoxicity was assessed using MTT assay against human prostate cancer PC3 cells. Metabolite profiling through LC-MS was performed to identify bioactive compounds. Molecular identification was confirmed by 16 S rRNA sequencing (Accession: MZ021336.1).

[RESULTS] The isolate displayed robust growth with distinct brown aerial and substrate mycelia on SCNA media. Antibacterial assays showed significant inhibition zones up to 24 mm against Bacillus cereus, Proteus vulgaris, Salmonella typhimurium, Staphylococcus aureus, and Pseudomonas aeruginosa. Protein purification enhanced specific antibacterial activity by 10.75-fold, with a recovery of 9.25%. MTT assay demonstrated a dose-dependent reduction in PC3 cell viability, reaching 51.85% inhibition at 200 µg/mL. LC-MS analysis confirmed the presence of Tryprostatin B, an indole alkaloid associated with anticancer effects.

[CONCLUSION] Streptomyces viridiostaticus from mangrove soil represents a promising source of antibacterial proteins and anticancer metabolites, highlighting the pharmaceutical value of marine-derived actinomycetes and their potential role in the discovery of novel therapeutic agents.