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Biofilm formation is important for microbial survival, adaptation, and persistence within mutualistic and pathogenic systems in the Vibironaceae. Biofilms offer protection against environmental stressors, immune responses, and antimicrobial treatments by increasing host colonization and resilience. This review examines the mechanisms of biofilm formation in Vibrio species, focusing on quorum sensing, cyclic-di-GMP signaling, and host-specific adaptations that influence biofilm structure and function. We discuss how biofilms differ between mutualistic and pathogenic species based on environmental and host signals. Recent advances in omics technologies such as transcriptomics and metabolomics have enhanced research in biofilm regulation under different conditions. Horizontal gene transfer and phase variation promote the greater fitness of bacterial biofilms due to the diversity of environmental isolates that utilize biofilms to colonize host species. Despite progress, questions remain regarding the long-term effects of biofilm formation and persistence on host physiology and biofilm community dynamics. Research integrating multidisciplinary approaches will help advance our understanding of biofilms and their implications for influencing microbial adaptation, symbiosis, and disease. These findings have applications in biotechnology and medicine, where the genetic manipulation of biofilm regulation can enhance or disrupt microbiome stability and pathogen resistance, eventually leading to targeted therapeutic strategies. 

ABSTRACT Many female squids and cuttlefishes have a symbiotic reproductive organ called the accessory nidamental gland (ANG) that hosts a bacterial consortium involved with egg defense against pathogens and fouling organisms. While the ANG is found in multiple cephalopod families, little is known about the global microbial diversity of these ANG bacterial symbionts. We used 16S rRNA gene community analysis to characterize the ANG microbiome from different cephalopod species and assess the relationship between host and symbiont phylogenies. The ANG microbiome of 11 species of cephalopods from four families (superorder: Decapodiformes) that span seven geographic locations was characterized. Bacteria of classAlphaproteobacteria, Gammaproteobacteria, andFlavobacteriiawere found in all species, yet analysis of amplicon sequence variants by multiple distance metrics revealed a significant difference between ANG microbiomes of cephalopod families (weighted/unweighted UniFrac, Bray–Curtis,P= 0.001). Despite being collected from widely disparate geographic locations, members of the family Sepiolidae (bobtail squid) shared many bacterial taxa including (~50%)Opitutae(Verrucomicrobia) andRuegeria(Alphaproteobacteria) species. Furthermore, we tested for phylosymbiosis and found a positive correlation between host phylogenetic distance and bacterial community dissimilarity (Mantel testr= 0.7). These data suggest that closely related sepiolids select for distinct symbionts from similar bacterial taxa. Overall, the ANGs of different cephalopod species harbor distinct microbiomes and thus offer a diverse symbiont community to explore antimicrobial activity and other functional roles in host fitness. IMPORTANCEMany aquatic organisms recruit microbial symbionts from the environment that provide a variety of functions, including defense from pathogens. Some female cephalopods (squids, bobtail squids, and cuttlefish) have a reproductive organ called the accessory nidamental gland (ANG) that contains a bacterial consortium that protects eggs from pathogens. Despite the wide distribution of these cephalopods, whether they share similar microbiomes is unknown. Here, we studied the microbial diversity of the ANG in 11 species of cephalopods distributed over a broad geographic range and representing 15–120 million years of host divergence. The ANG microbiomes shared some bacterial taxa, but each cephalopod species had unique symbiotic members. Additionally, analysis of host–symbiont phylogenies suggests that the evolutionary histories of the partners have been important in shaping the ANG microbiome. This study advances our knowledge of cephalopod–bacteria relationships and provides a foundation to explore defensive symbionts in other systems.