The HD-GYP domain protein of Shewanella putrefaciens YZ08 regulates biofilm formation and spoilage activities

Shewanella putrefaciens is an important spoilage bacteria in seafood and its ability to form biofilms in food processing environments increases the chances of food spoilage. Exploring the regulatory factors associated with biofilm formation and spoilage activity in S. putrefaciens is of great significance for extending the shelf life of seafood. In this work, the regulatory function of HD-GYP domain protein K2227_17660 in spoilage microorganism S. putrefaciens YZ08 was studied. The deletion mutant Δ17660 was developed to explore the effects of K2227_17660 in c-di-GMP content regulation, motility, biofilm formation, extracellular protease activity, and spoilage potential by phenotypic and transcriptional comparison with wild-type (WT) strain. Deletion of K2227_17660 significantly increased c-di-GMP content, biofilm biomass, the production of extracellular polysaccharide, trimethylamine (TMA), and putrescine compared with WT strains, and also affected membrane fatty acid composition. Furthermore, RT-qPCR results revealed the expression levels of genes associated with biofilm biomass, spoilage and unsaturated fatty acids (UFAs) synthesis changed in a manner consistent with the phenotypes. Our results indicated that K2227_17660 possesses phosphodiesterase (PDE) activity that controls the biofilm biomass and spoilage potential of S. putrefaciens. This study provided a basis for a correlation between c-di-GMP and food spoilage in S. putrefaciens, providing new insights into the control of food quality and safety.