The growing threat of antimicrobial resistance has renewed the search for novel bioactive natural products, with marine invertebrate microbiomes recognized as rich but under-exploited reservoirs of chemical diversity. Coral-associated bacteria, however, remain largely unexplored by genomics-guided bioprospection studies. This thesis presents the first genome-mining-based characterisation of the secondary metabolism of the cultivable bacterial community associated with the temperate octocoral Leptogorgia sarmentosa.
Ninety-four bacterial isolates were genome-sequenced, taxonomically classified, and mined for biosynthetic gene clusters. The collection proved remarkably novel, with 76% of isolates representing potentially novel species in addition to at least one candidate novel genus. The biosynthetic repertoire encompassed 615 biosynthetic gene clusters (BGCs), dominated by RiPPs (26.7%), NRPS (12.8%), terpenes (12.7%), PKS (8.0%), and NRPS-PKS hybrids (7.2%), with only 9.4% matching characterized chemistry in MIBiG. Cross-genus gene cluster families included a clade-conserved Roseobacteraceae quorum-sensing system (GCF_45), a Stappiaceae-associated terpene cluster (GCF_11), and a candidate cross-Vibrionaceae β-lactone biosynthetic system (GCF_50), all prioritised for downstream characterisation.
These findings establish the cultivable bacteriome of L. sarmentosa as an under-explored reservoir of novel microbial taxonomy and chemistry and provide a genome-level foundation for future investigations of natural products from the temperate-octocoral holobiont and its biotechnological potential.
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