c-di-GMP-Mediated Biofilm Regulation in Specific Spoilage Organisms: Mechanisms and Control Strategies in Aquatic Products.

Aquatic product spoilage primarily results from specific spoilage organisms (SSOs) such as Pseudomonas, Aeromonas, and Shewanella, with biofilm formation playing a pivotal role in accelerating deterioration. The bacterial second messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) orchestrates this process by regulating biofilm assembly. Intracellular c-di-GMP levels, modulated by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), dictate bacterial behavior: higher concentrations suppress motility, promote adhesion, and trigger extracellular polymeric substance (EPS) secretion, reinforcing biofilm integrity. This protective matrix enhances SSO resistance to refrigeration, antimicrobial agents, and environmental stressors. Within biofilms, SSOs display heightened metabolic activity, producing proteases and lipases that degrade proteins and lipids, yielding spoilage metabolites such as trimethylamine, hydrogen sulfide, and organic acids-compounds responsible for off-odors, texture deterioration, and quality loss. Interventions targeting c-di-GMP signaling, such as DGC/PDE inhibitors, quorum-sensing disruption, and combined physical-chemical treatments, may effectively suppress biofilm formation and prolong shelf life. Further studies should elucidate c-di-GMP's interactions with other regulatory networks and its influence on multispecies biofilm dynamics in aquatic products. This review examines biofilm formation and its role in aquatic product spoilage, along with c-di-GMP's regulatory function in spoilage-associated biofilms and its broader spoilage implications, offering a theoretical foundation for further research on c-di-GMP-mediated interactions in multispecies biofilm systems.