Cyclic diguanylate (c-di-GMP) is a second messenger involved in the regulation of various physiological processes in bacteria. However, its function in spoilage bacteria has not yet been addressed. Here, we studied the function of a tandem GGDEF-EAL domain protein, Sbal_3235, in the spoilage bacterium Shewanella baltica OS155. The deletion of sbal_3235 significantly reduced the c-di-GMP level, biofilm formation, and exopolysaccharide, trimethylamine (TMA), and putrescine production; sbal_3235 deletion also downregulated the expression of the torS and speF genes and affected membrane fatty acid composition. Site-directed mutagenesis in conserved GGDEF and EAL motifs abolished diguanylate cyclase (DGC) and phosphodiesterase (PDE) activity, respectively. These data indicate that Sbal_3235 is an essential contributor to the c-di-GMP pool with bifunctional DGC and PDE activity, which is involved in the biofilm formation and spoilage activity of S. baltica OS155. Our findings expand the biochemical role of c-di-GMP and uncover its link to spoilage activities, providing novel targets for food quality and safety controlling.

中文翻译：

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串联的GGDEF-EAL域蛋白调节的c-di-GMP信号有助于波罗的海希瓦氏菌OS155的腐败相关活动。

环状双鸟苷酸（c-di-GMP）是第二种信使，参与调节细菌的各种生理过程。然而，其在腐败细菌中的功能尚未得到解决。在这里，我们研究了在腐败细菌波罗的海希瓦氏菌OS155中串联的GGDEF-EAL域蛋白Sbal_3235的功能。sbal_3235的缺失显着降低了c-di-GMP水平，生物膜形成以及胞外多糖，三甲胺（TMA）和腐胺的产生；sbal_3235缺失还下调了torS和speF基因的表达并影响了膜脂肪酸的组成。保守的GGDEF和EAL基序中的定点诱变分别消除了双鸟苷酸环化酶（DGC）和磷酸二酯酶（PDE）的活性。这些数据表明，Sbal_3235是具有双功能DGC和PDE活性的c-di-GMP库的重要贡献者，它参与了Baltica OS155的生物膜形成和腐败活动。我们的发现扩大了c-di-GMP的生化作用，并揭示了其与腐败活动的联系，为食品质量和安全控制提供了新的目标。