Bacterial Cyclic AMP-Phosphodiesterase Activity Coordinates Biofilm Formation

Biofilm-related infections are a major contributor to human disease, and the capacity for surface attachment and biofilm formation are key attributes for the pathogenesis of microbes. Serratia marcescens type I fimbriae-dependent biofilms are coordinated by the adenylate cyclase, CyaA, and the cyclic 3′,5′-adenosine monophosphate (cAMP)-cAMP receptor protein (CRP) complex. This study uses S. marcescens as a model system to test the role of cAMP-phosphodiesterase activity in controlling biofilm formation. Herein we describe the characterization of a putative S. marcescens cAMP-phosphodiesterase gene (SMA3506), designated as cpdS, and demonstrated to be a functional cAMP-phosphodiesterase both in vitro and in vivo. Deletion of cpdS resulted in defective biofilm formation and reduced type I fimbriae production, whereas multicopy expression of cpdS conferred a type I fimbriae-dependent hyper-biofilm. Together, these results support a model in which bacterial cAMP-phosphodiesterase activity modulates biofilm formation.

生物膜相关感染是人类疾病的重要诱因，而表面附着与生物膜形成能力是微生物致病过程的关键特征。黏质沙雷氏菌（Serratia marcescens）I型菌毛依赖型生物膜的形成由腺苷酸环化酶（adenylate cyclase, CyaA）以及环3′,5′-腺苷一磷酸（cyclic 3′,5′-adenosine monophosphate, cAMP）-cAMP受体蛋白（CRP）复合物协同调控。本研究以黏质沙雷氏菌为模型体系，探究cAMP磷酸二酯酶活性在调控生物膜形成中的作用。本研究对推定的黏质沙雷氏菌cAMP磷酸二酯酶基因SMA3506（命名为cpdS）进行了表征，并证实其在体外与体内均具备功能性cAMP磷酸二酯酶活性。敲除cpdS会导致生物膜形成缺陷以及I型菌毛生成量降低；而cpdS的多拷贝表达则可赋予菌株I型菌毛依赖的超量生物膜形成能力。综上，上述结果支持"细菌cAMP磷酸二酯酶活性可调控生物膜形成"这一模型。