Comparative Genome Mining of Jiangella sp. GA3 from Turtle-Ingested Plastic Reveals Conserved Biosynthetic Gene Clusters

Abstract

Rare actinobacteria are promising sources of specialized metabolites, yet genome mining still prioritizes genomes encoding many biosynthetic gene clusters (BGCs) rather than clusters that are distant from characterized chemistry. Here, we describe the isolation of a novel Jiangella strain reported from a marine, animal-associated plastisphere and place its biosynthetic repertoire in the context of the whole genus, providing a genome-based prioritization of candidate biosynthetic targets. Digital DNA-DNA hybridization (57.8%) and OrthoANIu (94.65%) values against its closest relative, J. alba DSM 45237ᵀ, support its assignment as a candidate novel species, although formal species description will require additional phenotypic and chemotaxonomic characterization. antiSMASH predicted twelve BGCs, within the range observed across the genus (7–13), of which only one matched a characterized pathway, and the Biosynthetic Novelty Index of the genome was 865.3, the fourth highest among the twelve genomes analyzed. Across these genomes, 124 BGCs grouped into 70 gene cluster families, 74% of them strain-specific. Two families without any characterized representative, a lasso-peptide family and a RiPP recognition element-containing family, were instead conserved across a subclade, down to nearly identical precursor peptides. No antimicrobial activity was detected under the conditions tested. Genus-wide comparison therefore identifies conserved yet uncharacterized families as rational priorities that cluster counts alone would miss.