VqsA, a Novel LysR-Type Transcriptional Regulator, Coordinates Quorum Sensing (QS) and Is Controlled by QS To Regulate Virulence in the Pathogen Vibrio alginolyticus

• Published in: Applied and environmental microbiology 2018-06, Vol.84 (12), p.e00444-18
• Main Authors: Gao, Xiating, Wang, Xuetong, Mao, Qiaoqiao, Xu, Rongjing, Zhou, Xiaohui, Ma, Yue, Liu, Qin, Zhang, Yuanxing, Wang, Qiyao
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - genetics; Binding Sites; Biofilms; Cell density; Density; Deoxyribonuclease; Electrophoretic mobility; Environmental Microbiology; Exotoxins; Feedback inhibition; Footprinting; Gene expression; Gene Expression Regulation, Bacterial; Genes; Pathogens; Phenotypes; Promoter Regions, Genetic; Quorum sensing; Quorum Sensing - genetics; Regulators; Repressor Proteins - genetics; Screens; Secretion; Trans-Activators - genetics; Transcription factors; Transcription Factors - genetics; Vibrio alginolyticus; Vibrio alginolyticus - genetics; Vibrio alginolyticus - pathogenicity; Virulence; Waterborne diseases
• ISSN: 0099-2240; 1098-5336; 1098-5336
• DOI: 10.1128/AEM.00444-18

The quorum sensing (QS) system controls bacterial group behaviors in response to cell density. In vibrios, LuxR and AphA are two master QS regulators (MQSRs) controlling gene expression in response to high or low cell density. Other regulators involved in the regulation of these two MQSRs and QS pathways remain to be determined. Here, we performed bacterial one-hybrid (B1H)-assay-based screens of transcriptional factors (TFs) to identify TFs that can directly regulate the expression of and from a library of 285 TFs encoded by the fish pathogen A total of 7 TFs were identified to bind to the promoters of both and Among these TFs, the novel LysR-type transcriptional regulator (LTTR) VqsA could activate LuxR and repress AphA transcription. Meanwhile, LuxR and AphA exerted feedback inhibition and activation of expression, respectively, indicating that VqsA coordinates QS and is also regulated by QS. In addition, VqsA inhibited its own expression by directly binding to its own promoter region. The VqsA-binding sites in the promoter regions of and as well as the binding sites of LuxR, AphA, and VqsA in the gene were uncovered by electrophoretic mobility shift assays (EMSAs) and DNase I footprinting analysis. Finally, VqsA was verified to play essential roles in QS-regulated phenotypes, i.e., type VI secretion system 2 (T6SS2)-dependent interbacterial competition, biofilm formation, exotoxin production, and virulence of Collectively, our data showed that VqsA is an important QS regulator in Investigation of the mechanism of regulation of quorum sensing (QS) systems will facilitate an understanding of bacterial pathogenesis and the identification of effective QS interference (QSI) targets. Here, we systematically screened transcriptional factors (TFs) that modulate the expression of the master QS regulators (MQSRs) LuxR and AphA, and a novel LysR-type transcriptional regulator, VqsA, was identified. Our data illuminated the mechanisms mediating the interaction among LuxR, AphA, and VqsA as well as the effects of these regulators on the expression and output of QS. The impaired expression of virulence genes as a result of disruption demonstrated that VqsA is an important player in QS regulation and pathogenesis and may be the third MQSR involved in sensing environmental signals by vibrios to coordinate QS responses. This study will facilitate the development of strategies to interfere with QS and effectively control this pathogen that plagues the aquaculture indust