Members of the genus Pseudoalteromonas are ecologically versatile marine bacteria involved in nutrient cycling, chemical signaling, and competition for resources via bioactive compound production. Here, we characterize the genomic and functional diversity of 19 Pseudoalteromonas isolates from the bivalve Anadara tuberculosa to elucidate ecological strategies enabling coexistence in host-associated environments. Whole-genome sequencing and phylogenomic inference revealed extensive genomic diversity, with most isolates affiliated with recognized taxa and two genomically distinct lineages representing candidate novel species. Functional profiling with Traitar identified 67 traits related to enzymatic activity, substrate utilization, and environmental tolerance, revealing a bimodal structure: one assemblage (Pseudoalteromonas maricaloris, Pseudoalteromonas xiamenensis, Pseudoalteromonas piscicida) exhibited diverse biosynthetic pathways consistent with chemical competition strategies, while a second assemblage including the two candidate species displayed broader carbohydrate utilization with streamlined biosynthetic capacity. Notably, unique non-NRPS siderophore clusters in Pseudoalteromonas gelatinilytica and one candidate species suggest alternative iron acquisition strategies adapted to host-associated niches. Principal coordinate analysis revealed two distinct ecological assemblages, indicating that functional differentiation through niche partitioning rather than direct competition enables coexistence of phylogenetically related populations within the bivalve microbiome. Comparative genomic metrics (ANI, AAI, dDDH) support the proposal of Pseudoalteromonas pianguae sp. nov. and Pseudoalteromonas iscuandensis sp. nov., expanding the known diversity of this ecologically important genus. This genome-informed approach provides mechanistic insight into bacterial diversification in tropical bivalve holobionts and establishes a foundation for exploring Pseudoalteromonas-mediated interactions in marine invertebrate microbiomes.
Benavides et al. (Fri,) studied this question.