The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin

ABSTRACT Resistance-nodulation-division (RND) superfamily efflux systems have been widely studied for their role in antibiotic resistance, but their native biological functions remain poorly understood. We previously showed that loss of RND-mediated efflux in Vibrio cholerae resulted in activation o...

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Autores principales:	Dillon E. Kunkle, X. Renee Bina, James E. Bina
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2017
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/defbabad81864ccbbd5399c3eef47270
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spelling	oai:doaj.org-article:defbabad81864ccbbd5399c3eef472702021-11-15T15:51:29ZThe <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin10.1128/mBio.00126-172150-7511https://doaj.org/article/defbabad81864ccbbd5399c3eef472702017-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00126-17https://doaj.org/toc/2150-7511ABSTRACT Resistance-nodulation-division (RND) superfamily efflux systems have been widely studied for their role in antibiotic resistance, but their native biological functions remain poorly understood. We previously showed that loss of RND-mediated efflux in Vibrio cholerae resulted in activation of the Cpx two-component regulatory system, which mediates adaptation to stress resulting from misfolded membrane proteins. Here, we investigated the mechanism linking RND-mediated efflux to the Cpx response. We performed transposon mutagenesis screening of RND-deficient V. cholerae to identify Cpx suppressors. Suppressor mutations mapped to genes involved in the biosynthesis of the catechol siderophore vibriobactin. We subsequently demonstrated that vibriobactin secretion is impaired in mutants lacking the VexGH RND efflux system and that impaired vibriobactin secretion is responsible for Cpx system activation, suggesting that VexGH secretes vibriobactin. This conclusion was bolstered by results showing that vexGH expression is induced by iron limitation and that vexH-deficient cells exhibit reduced fitness during growth under iron-limiting conditions. Our results support a model where VexGH contributes to cellular homeostasis by effluxing vibriobactin. In the absence of vexGH, retained vibriobactin appears to chelate iron from iron-rich components of the respiratory chain, with the deferrated proteins functioning to activate the Cpx response. Our collective results demonstrate that a native function of the V. cholerae VexGH RND efflux system is in vibriobactin secretion and that vibriobactin efflux is critical for maintenance of cellular homeostasis. IMPORTANCE RND efflux systems are ubiquitous Gram-negative transporters that play critical roles in antimicrobial resistance. In addition to antimicrobial resistance, RND transporters also affect the expression of diverse phenotypes, including virulence, cell metabolism, and stress responses. The latter observations suggest that RND transporters fulfill unknown physiological functions in the cell independently of their role in antimicrobial resistance. Vibrio cholerae is representative of many Gram-negative bacteria in encoding multiple RND transporters that are redundant in antimicrobial resistance and affect multiple phenotypes. Here we describe a novel function of the V. cholerae VexGH RND transporter in vibriobactin secretion. We show that vibriobactin production in VexGH-deficient cells impacts cell homeostasis, leading to activation of the Cpx stress response and reduced fitness under iron-limiting conditions. Our results highlight a native physiological function of an RND transporter and provide insight into the selective forces that maintain what was thought to be a redundant multidrug transporter.Dillon E. KunkleX. Renee BinaJames E. BinaAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 8, Iss 3 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Dillon E. Kunkle X. Renee Bina James E. Bina The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin
description	ABSTRACT Resistance-nodulation-division (RND) superfamily efflux systems have been widely studied for their role in antibiotic resistance, but their native biological functions remain poorly understood. We previously showed that loss of RND-mediated efflux in Vibrio cholerae resulted in activation of the Cpx two-component regulatory system, which mediates adaptation to stress resulting from misfolded membrane proteins. Here, we investigated the mechanism linking RND-mediated efflux to the Cpx response. We performed transposon mutagenesis screening of RND-deficient V. cholerae to identify Cpx suppressors. Suppressor mutations mapped to genes involved in the biosynthesis of the catechol siderophore vibriobactin. We subsequently demonstrated that vibriobactin secretion is impaired in mutants lacking the VexGH RND efflux system and that impaired vibriobactin secretion is responsible for Cpx system activation, suggesting that VexGH secretes vibriobactin. This conclusion was bolstered by results showing that vexGH expression is induced by iron limitation and that vexH-deficient cells exhibit reduced fitness during growth under iron-limiting conditions. Our results support a model where VexGH contributes to cellular homeostasis by effluxing vibriobactin. In the absence of vexGH, retained vibriobactin appears to chelate iron from iron-rich components of the respiratory chain, with the deferrated proteins functioning to activate the Cpx response. Our collective results demonstrate that a native function of the V. cholerae VexGH RND efflux system is in vibriobactin secretion and that vibriobactin efflux is critical for maintenance of cellular homeostasis. IMPORTANCE RND efflux systems are ubiquitous Gram-negative transporters that play critical roles in antimicrobial resistance. In addition to antimicrobial resistance, RND transporters also affect the expression of diverse phenotypes, including virulence, cell metabolism, and stress responses. The latter observations suggest that RND transporters fulfill unknown physiological functions in the cell independently of their role in antimicrobial resistance. Vibrio cholerae is representative of many Gram-negative bacteria in encoding multiple RND transporters that are redundant in antimicrobial resistance and affect multiple phenotypes. Here we describe a novel function of the V. cholerae VexGH RND transporter in vibriobactin secretion. We show that vibriobactin production in VexGH-deficient cells impacts cell homeostasis, leading to activation of the Cpx stress response and reduced fitness under iron-limiting conditions. Our results highlight a native physiological function of an RND transporter and provide insight into the selective forces that maintain what was thought to be a redundant multidrug transporter.
format	article
author	Dillon E. Kunkle X. Renee Bina James E. Bina
author_facet	Dillon E. Kunkle X. Renee Bina James E. Bina
author_sort	Dillon E. Kunkle
title	The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin
title_short	The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin
title_full	The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin
title_fullStr	The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin
title_full_unstemmed	The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin
title_sort	<italic toggle="yes">vibrio cholerae</italic> vexgh rnd efflux system maintains cellular homeostasis by effluxing vibriobactin
publisher	American Society for Microbiology
publishDate	2017
url	https://doaj.org/article/defbabad81864ccbbd5399c3eef47270
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The <italic toggle="yes">Vibrio cholerae</italic> VexGH RND Efflux System Maintains Cellular Homeostasis by Effluxing Vibriobactin

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