The quorum sensing transcription factor AphA directly regulates natural competence inVibrio cholerae

Abstract

1Many bacteria use population density to control gene expression via quorum sensing. In Vibrio 2 cholerae, quorum sensing coordinates virulence, biofilm formation, and DNA uptake by natural 3 competence. The transcription factors AphA and HapR, expressed at low-and high-cell density 4 respectively, play a key role. In particular, AphA triggers the entire virulence cascade upon host 5 colonisation. In this work we have mapped genome-wide DNA binding by AphA. We show that 6AphA is versatile, exhibiting distinct modes of DNA binding and promoter regulation. 7Unexpectedly, whilst HapR is known to induce natural competence, we demonstrate that AphA 8 also intervenes. Most notably, AphA is a direct repressor of tfoX, the master activator of 9 competence. Hence, production of AphA markedly suppressed DNA uptake; an effect largely 10 circumvented by ectopic expression of tfoX. Our observations suggest dual regulation of 11 competence. At low cell density AphA is a master repressor whilst HapR activates the process at 12 high cell density. Thus, we provide deep mechanistic insight into the role of AphA and highlight 13 how V. cholerae utilises this regulator for diverse purposes. 14 AUTHOR SUMMARY 15Cholera remains a devastating diarrhoeal disease responsible for millions of cases, thousands of deaths, 16 and a $3 billion financial burden every year. Although notorious for causing human disease, the 17 microorganism responsible for cholera is predominantly a resident of aquatic environments. Here, the 18 organism survives in densely packed communities on the surfaces of crustaceans. Remarkably, in this 19 situation, the microbe can feast on neighbouring cells and acquire their DNA. This provides a useful 20 food source and an opportunity to obtain new genetic information. In this paper, we have investigated 21 how acquisition of DNA from the local environment is regulated. We show that a "switch" within the 22 microbial cell, known to activate disease processes in the human host, also controls DNA uptake. Our 23 results explain why DNA scavenging only occurs in suitable environments and illustrates how 24 interactions between common regulatory switches affords precise control of microbial behaviours. 25Quorum sensing detects changes in bacterial population density reported by auto-inducer molecules 36[17]. This information is used to modify patterns of gene expression [18]. For example, CqsS is a 37 membrane bound sensor kinase that detects cholera auto-inducer 1 (CAI-1) [19]. When kin are scarce, 38and CAI-1 levels low, CqsS triggers a regulatory cascade, which cumulates in expression of five quorum 39 regulatory RNAs [20]. These RNA molecules activate translation of AphA, a PadR family transcription 40 factor with an N-terminal winged helix-turn-helix DNA binding motif [20][21][22]. In turn, AphA activates 41 expression of tcpPH [23]. This event ignites the entire virulence gene expression programme [16]. 42 Surprisingly, given the central role of AphA, the regulator is poorly understood. For instance, 43 transcriptome ...

A Comprehensive Coexpression Network Analysis in Vibrio cholerae

“…2F ). This subnetwork includes high-level transcriptional regulators, such as AphA, TfoS, and TfoY, with known roles mediating the complex interplay between quorum sensing, natural competence, type VI secretion, and other related pathways ( 32 – 37 ). As each of these transcription factors is involved in a multitude of cellular processes and significantly coexpresses with hundreds of other genes, our analysis describes their closest connections under parameters designed to find meaningful and practically interpretable relationships.…”

Antimicrobial resistance in enteric bacteria: current state and next-generation solutions

“… 50 Vibrio achieves extensive antibiotic resistance through its natural competency, allowing it to take up mobile genetic elements (MGEs) including plasmids, integrons, conjugative transposons, and SXT elements ( Table 1 ). 30 , 63 , 64 SXT elements, named for early observations of their conferred resistance to sulfamethoxazole and trimethoprim, are a type of integrative and conjugative element (ICE) that can confer additional resistance to agents such as streptomycin, nalidixic acid, and tetracycline. 29 Similar to other diarrheal pathogens, V. cholerae acquires QRDR mutations that result in fluoroquinolone resistance, and can acquire diverse classes of efflux pumps conferring resistance to agents such as erythromycin, penicillins, novobiocin, and polymyxin B ( Table 1 ).…”

Vibrio Pathogenicity Island-1: The Master Determinant of Cholera Pathogenesis

“…The low cell density of the pathogen in the gut is typically sensed by a membrane bound sensor kinase (the CqsS), based on the concentration of a cholera auto-inducer 1 (CAI-1). CAI-1 triggers the expression of aphA , which induces the expression of tcpP and tcpH (Haycocks et al, 2019 ; Herzog et al, 2019 ). This quorum sensing of V. cholerae modulates the virulence gene expression cascades for development of the disease and its severity.…”