Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX

ABSTRACT Bacillus anthracis—a Gram-positive, spore-forming bacterium—causes anthrax, a highly lethal disease with high bacteremia titers. Such rapid growth requires ample access to nutrients, including iron. However, access to this critical metal is heavily restricted in mammals, which requires B. a...

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Autores principales:	A. K. Hagan, A. Tripathi, D. Berger, D. H. Sherman, P. C. Hanna
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2017
Materias:	Bacillus anthracis iron acquisition siderophores transporters Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/07df1c066a7341e792d63e5c076a0bd4
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spelling	oai:doaj.org-article:07df1c066a7341e792d63e5c076a0bd42021-11-15T15:51:51ZPetrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX10.1128/mBio.01238-172150-7511https://doaj.org/article/07df1c066a7341e792d63e5c076a0bd42017-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01238-17https://doaj.org/toc/2150-7511ABSTRACT Bacillus anthracis—a Gram-positive, spore-forming bacterium—causes anthrax, a highly lethal disease with high bacteremia titers. Such rapid growth requires ample access to nutrients, including iron. However, access to this critical metal is heavily restricted in mammals, which requires B. anthracis to employ petrobactin, an iron-scavenging small molecule known as a siderophore. Petrobactin biosynthesis is mediated by asb gene products, and import of the iron-bound (holo)-siderophore into the bacterium has been well studied. In contrast, little is known about the mechanism of petrobactin export following its production in B. anthracis cells. Using a combination of bioinformatics data, gene deletions, and laser ablation electrospray ionization mass spectrometry (LAESI-MS), we identified a resistance-nodulation-cell division (RND)-type transporter, termed ApeX, as a putative petrobactin exporter. Deletion of apeX abrogated export of intact petrobactin, which accumulated inside the cell. However, growth of ΔapeX mutants in iron-depleted medium was not affected, and virulence in mice was not attenuated. Instead, petrobactin components were determined to be exported through a different protein, which enables iron transport sufficient for growth, albeit with a slightly lower affinity for iron. This is the first report to identify a functional siderophore exporter in B. anthracis and the in vivo functionality of siderophore components. Moreover, this is the first application of LAESI-MS to sample a virulence factor/metabolite directly from bacterial culture media and cell pellets of a human pathogen. IMPORTANCE Bacillus anthracis requires iron for growth and employs the siderophore petrobactin to scavenge this trace metal during infections. While we understand much about petrobactin biosynthesis and ferric petrobactin import, how apo-petrobactin (iron free) is exported remains unknown. This study used a combination of bioinformatics, genetics, and mass spectrometry to identify the petrobactin exporter. After screening 17 mutants with mutations of candidate exporter genes, we identified the apo-petrobactin exporter (termed ApeX) as a member of the resistance-nodulation-cell division (RND) family of transporters. In the absence of ApeX, petrobactin accumulates inside the cell while continuing to export petrobactin components that are capable of transporting iron. Thus, the loss of ApeX does not affect the ability of B. anthracis to cause disease in mice. This has implications for treatment strategies designed to target and control pathogenicity of B. anthracis in humans.A. K. HaganA. TripathiD. BergerD. H. ShermanP. C. HannaAmerican Society for MicrobiologyarticleBacillus anthracisiron acquisitionsiderophorestransportersMicrobiologyQR1-502ENmBio, Vol 8, Iss 5 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Bacillus anthracis iron acquisition siderophores transporters Microbiology QR1-502
spellingShingle	Bacillus anthracis iron acquisition siderophores transporters Microbiology QR1-502 A. K. Hagan A. Tripathi D. Berger D. H. Sherman P. C. Hanna Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX
description	ABSTRACT Bacillus anthracis—a Gram-positive, spore-forming bacterium—causes anthrax, a highly lethal disease with high bacteremia titers. Such rapid growth requires ample access to nutrients, including iron. However, access to this critical metal is heavily restricted in mammals, which requires B. anthracis to employ petrobactin, an iron-scavenging small molecule known as a siderophore. Petrobactin biosynthesis is mediated by asb gene products, and import of the iron-bound (holo)-siderophore into the bacterium has been well studied. In contrast, little is known about the mechanism of petrobactin export following its production in B. anthracis cells. Using a combination of bioinformatics data, gene deletions, and laser ablation electrospray ionization mass spectrometry (LAESI-MS), we identified a resistance-nodulation-cell division (RND)-type transporter, termed ApeX, as a putative petrobactin exporter. Deletion of apeX abrogated export of intact petrobactin, which accumulated inside the cell. However, growth of ΔapeX mutants in iron-depleted medium was not affected, and virulence in mice was not attenuated. Instead, petrobactin components were determined to be exported through a different protein, which enables iron transport sufficient for growth, albeit with a slightly lower affinity for iron. This is the first report to identify a functional siderophore exporter in B. anthracis and the in vivo functionality of siderophore components. Moreover, this is the first application of LAESI-MS to sample a virulence factor/metabolite directly from bacterial culture media and cell pellets of a human pathogen. IMPORTANCE Bacillus anthracis requires iron for growth and employs the siderophore petrobactin to scavenge this trace metal during infections. While we understand much about petrobactin biosynthesis and ferric petrobactin import, how apo-petrobactin (iron free) is exported remains unknown. This study used a combination of bioinformatics, genetics, and mass spectrometry to identify the petrobactin exporter. After screening 17 mutants with mutations of candidate exporter genes, we identified the apo-petrobactin exporter (termed ApeX) as a member of the resistance-nodulation-cell division (RND) family of transporters. In the absence of ApeX, petrobactin accumulates inside the cell while continuing to export petrobactin components that are capable of transporting iron. Thus, the loss of ApeX does not affect the ability of B. anthracis to cause disease in mice. This has implications for treatment strategies designed to target and control pathogenicity of B. anthracis in humans.
format	article
author	A. K. Hagan A. Tripathi D. Berger D. H. Sherman P. C. Hanna
author_facet	A. K. Hagan A. Tripathi D. Berger D. H. Sherman P. C. Hanna
author_sort	A. K. Hagan
title	Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX
title_short	Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX
title_full	Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX
title_fullStr	Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX
title_full_unstemmed	Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX
title_sort	petrobactin is exported from <italic toggle="yes">bacillus anthracis</italic> by the rnd-type exporter apex
publisher	American Society for Microbiology
publishDate	2017
url	https://doaj.org/article/07df1c066a7341e792d63e5c076a0bd4
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Petrobactin Is Exported from <italic toggle="yes">Bacillus anthracis</italic> by the RND-Type Exporter ApeX

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