Quorum quenching, which disrupts quorum sensing (QS) by either degradation of QS signals or interference of signal generation or perception, is a promising strategy for the prevention and control of QS-mediated bacterial infections. Diffusible signal factor (DSF) is widely conserved in many Gram-negative bacterial pathogens. In this study, we developed an efficient method for screening of highly active DSF degradation microorganisms. Among them, Pseudomonas sp. strain HS-18 showed a superior DSF degradation activity. Bioinformatics and genetic analyses showed that at least 4 genes, designated digA to digD, encoding fatty acyl coenzyme A ligase homologues, are responsible for DSF signal degradation. Interestingly, all 4 dig genes were induced by exogenous DSF, with digA being the most significantly induced. Expression of the dig genes in Xanthomonas campestris pv. campestris markedly reduced the accumulation of endogenous DSF, decreased production of virulence factors, and attenuated bacterial virulence on host plants. Similarly, application of strain HS-18 as a biocontrol agent could substantially reduce the disease severity caused by X. campestris pv. campestris. These results unveil the molecular basis of a highly efficient DSF degradation bacterial isolate and present useful genes and biocontrol agents for control of the infectious diseases caused by DSF-dependent bacterial pathogens.

IMPORTANCE Diffusible signal factor (DSF) represents a family of widely conserved quorum sensing signals involved in the regulation of virulence factor production in many Gram-negative bacterial pathogens. In this study, we developed a novel and efficient method for screening highly active DSF degradation microorganisms. With this method, we identified a bacterial isolate, Pseudomonas sp. strain HS-18, with a superb DSF degradation activity. We further found that strain HS-18 contains 4 genes responsible for DSF signal degradation, and significantly, these were induced by exogenous DSF molecules. These findings unveil the molecular basis of a highly efficient DSF degradation bacterial isolate and present useful methods, genes, and agents for control of the infectious diseases caused by DSF-dependent bacterial pathogens.

群体猝灭是通过QS信号的降解或信号生成或感知的干扰来破坏群体感应（QS）的方法，它是预防和控制QS介导的细菌感染的一种有前途的策略。扩散信号因子（DSF）在许多革兰氏阴性细菌病原体中被广泛保存。在这项研究中，我们开发了一种用于筛选高活性DSF降解微生物的有效方法。其中，假单胞菌属。HS-18菌株显示出优异的DSF降解活性。生物信息学和遗传分析表明，至少有4个基因（称为digA到digD）编码脂肪酰基辅酶A连接酶同源物，是导致DSF信号降解的原因。有趣的是，全部4挖基因是由外源DSF诱导的，其中digA诱导最明显。在表达挖掘在基因黄单胞菌光伏。樟脑明显降低了内源性DSF的积累，降低了毒力因子的产生，并减弱了宿主植物上的细菌毒力。类似地，菌株HS-18作为生物防治剂的应用可以大大降低由野油菜枯草杆菌引起的疾病严重程度。桔梗。这些结果揭示了高效DSF降解细菌分离物的分子基础，并提出了有用的基因和生物控制剂，用于控制由DSF依赖性细菌病原体引起的传染病。

重要信息扩散信号因子（DSF）代表了一个广泛保存的群体感应信号家族，涉及许多革兰氏阴性细菌病原体中毒力因子的产生。在这项研究中，我们开发了一种新颖且有效的方法来筛选高活性DSF降解微生物。通过这种方法，我们鉴定出细菌分离株，假单胞菌sp。HS-18菌株，具有出色的DSF降解活性。我们进一步发现，菌株HS-18包含4个负责DSF信号降解的基因，并且明显地，这些基因是由外源DSF分子诱导的。这些发现揭示了高效DSF降解细菌分离物的分子基础，并提出了用于控制由DSF依赖性细菌病原体引起的传染病的有用方法，基因和试剂。