Comparative genomics and microbiome profiling reveal a conserved Vibrio rich mucus microbiota of the Florida false coral ( <i>Ricordea florida</i> )

Abstract Mucus is a critical interface between marine invertebrates and their environment and plays key roles in host defense. Despite its ecological importance, little is known about the microbial communities associated with mucus-producing corallimorpharians. Here, we used a multi-omics approach to characterize the mucus microbiome and immune repertoire of the Florida false coral, Ricordea florida . Culture-dependent and culture-independent analyses revealed that R. florida mucus harbors a bacterial community distinct from surrounding seawater and consistently dominated by Vibrio species. Whole-genome sequencing of 13 cultured Vibrio isolates representing nine distinct lineages revealed substantial taxonomic diversity, including several highly divergent strains that may represent undescribed species. Comparative genomic analyses identified enrichment of genes associated with carbohydrate acquisition, glycoside hydrolysis, and host colonization, including multiple components of the Tad/Flp adhesion system, suggesting adaptation to the mucus microenvironment. To investigate host factors that may shape microbial associations, we assembled and annotated a host transcriptome from healthy and immune-challenged polyps. This analysis identified a diverse innate immune repertoire, including Toll-like receptors, NOD-like receptors, lectins, scavenger receptors, complement-associated proteins, antiviral defense pathways, and membrane attack complex/perforin domain-containing effectors. Together, these findings demonstrate that R. florida supports a conserved, Vibrio -rich mucus microbiome and possesses a complex innate immune system capable of mediating host-microbe interactions at the mucosal surface. This study provides a foundation for understanding microbial colonization, immune defense, and holobiont function in an understudied cnidarian lineage.