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Abstract The genusVibrioincludes serious human pathogens, and mollusks are a significant reservoir for species such asV.vulnificus.Vibriospecies encode PecS, a member of the multiple antibiotic resistance regulator (MarR) family of transcription factors;pecSis divergently oriented topecM, which encodes an efflux pump. We report here thatVibriospecies feature frequent duplications ofpecS-pecMgenes, suggesting evolutionary pressures to respond to distinct environmental situations. The singleV.vulnificusPecS binds two sites within thepecS-pecMintergenic region with Kd = 0.3 ± 0.1 nM, a binding that is attenuated by the ligands xanthine and urate, except when promoter DNA is saturated with PecS. A unique target is found in the intergenic region between genes encoding the nitric oxide sensing transcription factor, NsrR, andnod; thenod-encoded nitric oxide dioxygenase is important for preventing nitric oxide stress. Reporter gene assays show that PecS-mediated repression of gene expression can be relieved in presence of ligand. Since xanthine and urate are produced as part of the oxidative burst during host defenses and under molluscan hypoxia, we propose that these intermediates in the host purine degradation pathway function to promote bacterial survival during hypoxia and oxidative stress.
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Regulation of bacterial virulence genes by PecS family transcription factors
ABSTRACT Bacterial plant pathogens adjust their gene expression programs in response to environmental signals and host-derived compounds. This ensures that virulence genes or genes encoding proteins, which promote bacterial fitness in a host environment, are expressed only when needed. Such regulation is in the purview of transcription factors, many of which belong to the ubiquitous multiple antibiotic resistance regulator (MarR) protein family. PecS proteins constitute a subset of this large protein family. PecS has likely been distributed by horizontal gene transfer, along with the divergently encoded efflux pump PecM, suggesting its integration into existing gene regulatory networks. Here, we discuss the roles of PecS in the regulation of genes associated with virulence and fitness of bacterial plant pathogens. A comparison of phenotypes and differential gene expression associated with the disruption of pecS shows that functional consequences of PecS integration into existing transcriptional networks are highly variable, resulting in distinct PecS regulons. Although PecS universally binds to the pecS-pecM intergenic region to repress the expression of both genes, binding modes differ. A particularly relaxed sequence preference appears to apply for Dickeya dadantii PecS, perhaps to optimize its integration as a global regulator and regulate genes ancestral to the acquisition of pecS-pecM. Even inducing ligands for PecS are not universally conserved. It appears that PecS function has been optimized to match the unique regulatory needs of individual bacterial species and that its roles must be appreciated in the context of the regulatory networks into which it was recruited.
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- Award ID(s):
- 2153410
- PAR ID:
- 10626624
- Editor(s):
- O'Toole, George
- Publisher / Repository:
- ASM
- Date Published:
- Journal Name:
- Journal of Bacteriology
- Volume:
- 206
- Issue:
- 10
- ISSN:
- 0021-9193
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1128/jb.00302-24
