In silico exploration of the genomic repertoire of Iranian aquatic bacteria: Prophage carriage, bioactive compound potential, CRISPR-Cas immunity, and integrated defensive-metabolic islands

The unique and underexplored aquatic ecosystems of Iran represent a significant reservoir of microbial diversity. This study presents the first comprehensive genomic survey of 38 native Iranian bacterial strains from hypersaline lakes and wetlands, integrating in silico analyses of their secondary metabolome, bacteriocin potential, resident prophages, and genomic architecture. Our genome mining revealed a prolific capacity for secondary metabolite production, identifying dozens of biosynthetic gene clusters (BGCs). Ectoine biosynthesis was ubiquitous, underscoring its role as a key osmoprotectant, while diverse BGCs for terpenes, polyketides, and hybrid metabolites were also prevalent. Concurrently, we identified a wide array of ribosomally synthesized and post-translationally modified peptides (RiPPs), including known bacteriocins. Furthermore, we characterized eight high-quality prophages integrated within these genomes, encoding auxiliary genes such as carbohydrate-active enzymes (CAZymes) and putative <i>anti</i>-CRISPR (ACR) proteins. The bacterial hosts themselves were equipped with robust defense systems, with CRISPR-Cas loci, predominantly Type I, detected in most strains. Crucially, we identified multi-functional genomic islands that physically link BGCs with defense systems (e.g., CRISPR-Cas, restriction-modification) and prophage regions. We propose the "Fortress Hypothesis" to explain this architecture, wherein the co-localization of metabolite production and defense machinery protects metabolic investment against phage predation and genetic loss. This integrative genomic arrangement highlights a sophisticated co-evolutionary strategy for survival in extreme environments. Our findings position these indigenous bacteria as a promising genetic repository for discovering novel bioactive compounds, enzymes, and biotechnological tools, with implications for antibiotic discovery, CRISPR modulation, and understanding adaptive microbial genomics in extreme niches.