CalR is required for the expression of T6SS2 and the adhesion of Vibrio parahaemolyticus to HeLa cells
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ORIGINAL PAPER
CalR is required for the expression of T6SS2 and the adhesion of Vibrio parahaemolyticus to HeLa cells Lingyu Zhang1 · George Osei‑Adjei1 · Ying Zhang1 · He Gao3 · Wenhui Yang2 · Dongsheng Zhou2 · Xinxiang Huang1 · Huiying Yang2 · Yiquan Zhang1
Received: 13 November 2016 / Revised: 21 February 2017 / Accepted: 7 March 2017 © Springer-Verlag Berlin Heidelberg 2017
Abstract Vibrio parahaemolyticus expresses one major virulence determinant T6SS2, which is constituted into three putative operons, i.e., VPA1027-1024, VPA10431028, and VPA1044-1046. CalR, a LysR-type transcriptional regulator, was originally identified as a repressor of the swarming motility and T3SS1 gene expression. As shown in this study, CalR binds to the promoter-proximal region of each of the three operons to activate their transcription, and moreover, CalR activates the adhesion of V. parahaemolyticus to HeLa cells. In addition, competitive EMSAs demonstrated that CalR acts as an antagonist of H–NS in V. parahaemolyticus. Collectively, these studies confirmed a new physiological role for CalR in V. parahaemolyticus. Keywords Vibrio parahaemolyticus · T6SS2 · CalR
Communicated by Djamel DRIDER. * Xinxiang Huang [email protected] * Huiying Yang [email protected] * Yiquan Zhang [email protected] 1
School of Medicine, Jiangsu University, Zhenjiang 212013, Jiangsu, China
2
State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100000, China
3
State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Centre for Disease Control and Prevention, Beijing 102206, China
Introduction Vibrio parahaemolyticus, the leading cause of seafoodassociated diarrhea and gastroenteritis, is a Gram-negative bacterium that naturally inhabits estuarine and marine environments. Humans are commonly infected by V. parahaemolyticus due to the consumption of raw or undercooked seafood. The major virulence factors involved in the pathogenicity of V. parahaemolyticus include thermostable direct hemolysin (TDH), TDH-related hemolysin (TRH), type III secretion systems (T3SS1 and T3SS2), and type VI secretion systems (T6SS1 and T6SS2) (Raghunath 2014). Bacterial T6SS is a novel needle-like protein injection machinery that is involved in virulence, symbiosis, interbacterial interactions, and antipathogenesis (Records 2011). The pandemic V. parahaemolyticus strain RIMD2210633 possesses two T6SS loci, named as T6SS1 and T6SS2, respectively (Makino et al. 2003). T6SS1 (VP1386-1414) harbors 29 consecutive genes forming 7 putative operons, while T6SS2 (VPA1024-1046) is constituted by 23 consecutive genes in 3 putative operons, i.e., VPA1027-1024, VPA1043-1028, and VPA1044-1046 (Ma et al. 2012). T6SS1 is a major contributor to antibacterial activity that can enhance environmental fitness of V. parahaemolyticus in marine environments, while T6SS2 is designed for the adhesion of V. parahaemolyticus to host cells (Salo
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