Vibrio cholerae accessory colonisation factor AcfC: a chemotactic protein with a role in hyperinfectivity

Esmeralda Valiente,Cadi Davies,Maria Getino,Brendan W Wren,Jennifer M Ritchie,Dominic C Mills

doi:10.1038/s41598-018-26570-7

Abstract

Vibrio cholerae O1 El Tor is an aquatic Gram-negative bacterium responsible for the current seventh pandemic of the diarrheal disease, cholera. A previous whole-genome analysis on V. cholerae O1 El Tor strains from the 2010 epidemic in Pakistan showed that all strains contained the V. cholerae pathogenicity island-1 and the accessory colonisation gene acfC (VC_0841). Here we show that acfC possess an open reading frame of 770 bp encoding a protein with a predicted size of 28 kDa, which shares high amino acid similarity with two adhesion proteins found in other enteropathogens, including Paa in serotype O45 porcine enteropathogenic Escherichia coli and PEB3 in Campylobacter jejuni. Using a defined acfC deletion mutant, we studied the specific role of AcfC in V. cholerae O1 El Tor environmental survival, colonisation and virulence in two infection model systems (Galleria mellonella and infant rabbits). Our results indicate that AcfC might be a periplasmic sulfate-binding protein that affects chemotaxis towards mucin and bacterial infectivity in the infant rabbit model of cholera. Overall, our findings suggest that AcfC contributes to the chemotactic response of WT V. cholerae and plays an important role in defining the overall distribution of the organism within the intestine.

Highlights

Vibrio cholerae O1 El Tor is an aquatic, Gram-negative, single flagellated bacterium responsible for the current seventh cholera pandemic[1]
We provide a detailed characterisation of the V. cholerae O1 El Tor accessory colonisation factor, AcfC, which might be a sulfate-binding protein that enhances chemotaxis towards intestinal mucin and contributes to promoting the ‘correct’ localisation of WT V. cholerae in the small intestine
As mucus is rich in sulfated molecules[26] we hypothesize that AcfC might act as a ‘sulfate sensor’ of V. cholerae O1 El Tor that senses intestinal mucus and facilitates penetration of the mucus layer by directing chemotaxis towards sulfated molecules at the intestinal surface

Summary

Introduction

Vibrio cholerae O1 El Tor is an aquatic, Gram-negative, single flagellated bacterium responsible for the current seventh cholera pandemic[1]. CT is responsible for the profuse watery diarrhoea that characterises the disease[6] whereas TCP, a type IV pilus, is essential for V. cholerae colonisation of the small intestine, as demonstrated in both human volunteers[8] and animal models[9]. Recent studies[12,13] suggest that the distribution of Vibrio cholerae in the intestine is as a result of a complex interplay between motility, chemotaxis and host mucin. VPI-1 possesses a cluster of four accessory colonisation factor (acf) genes, designated as acfA, acfB, acfC and acfD16. Both TCP and acf genes are regulated by ToxR, the cholera toxin transcriptional activator[17]. We hypothesized that the presence of a functional acfC in V. cholerae may confer an advantage to strains in PSC-1 to survive in the environment and/or to colonise the human small intestine

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Results

Conclusion