Lrp, a global regulator, regulates the virulence of Vibrio vulnificus

Abstract

BackgroundAn attenuated mutant (designated NY303) of Vibrio vulnificus, which causes serious wound infection and septicemia in humans, was isolated fortuitously from a clinical strain YJ016. This mutant was defective in cytotoxicity, migration on soft agar and virulence in the mouse. The purpose of this study was to map the mutation in this attenuated mutant and further explore how the gene thus identified is involved in virulence.MethodsThe whole genome sequence of mutant NY303 determined by next-generation sequencing was compared with that of strain YJ016 to map the mutations. By isolating and characterizing the specific gene-knockout mutants, the gene associated with the phenotype of mutant NY303 was identified. This gene encodes a global regulator, Lrp. A mutant, YH01, deficient in Lrp was isolated and examined in vitro, in vivo and ex vivo to find the affected virulence mechanisms. The target genes of Lrp were further identified by comparing the transcriptomes, which were determined by RNA-seq, of strain YJ016 and mutant YH01. The promoters bound by Lrp were identified by genome footprinting-sequencing, and those related with virulence were further examined by electrophoretic mobility shift assay.ResultsA mutation in lrp was shown to be associated with the reduced cytotoxicity, chemotaxis and virulence of mutant NY303. Mutant YH01 exhibited a phenotype resembling that of mutant NY303, and was defective in colonization in the mouse and growth in mouse serum, but not the antiphagocytosis ability. 596 and 95 genes were down- and up-regulated, respectively, in mutant YH01. Many of the genes involved in secretion of the MARTX cytotoxin, chemotaxis and iron-acquisition were down-regulated in mutant YH01. The lrp gene, which was shown to be negatively autoregulated, and 7 down-regulated virulence-associated genes were bound by Lrp in their promoters. A 14-bp consensus sequence, mkCrTTkwAyTsTG, putatively recognized by Lrp was identified in the promoters of these genes.ConclusionsLrp is a global regulator involved in regulation of cytotoxicity, chemotaxis and iron-acquisition in V. vulnificus. Down-regulation of many of the genes associated with these properties may be responsible, at least partly, for loss of virulence in mutant NY303.Electronic supplementary materialThe online version of this article (doi:10.1186/s12929-017-0361-9) contains supplementary material, which is available to authorized users.

A MARTX Toxin rtxA Gene Is Controlled by Host Environmental Signals through a CRP-Coordinated Regulatory Network in Vibrio vulnificus

“…It has been reported that H-NS represses but HlyU derepresses rtxA transcription in V. vulnificus ( 36 ). In an effort to identify other transcription factor(s) associated with the rtxA regulation, the rtxA transcript levels were compared in the wild type and various isogenic mutants lacking transcription factors which are known to affect the expression of virulence genes in V. vulnificus ( 27 , 37 – 43 ). The rtxA transcript level in the lrp mutant was significantly lower than that in the wild type ( Fig.…”

Adaptation to host in Vibrio vulnificus, a zoonotic pathogen that causes septicemia in fish and humans

“…S2B). Our transcriptomic results also suggest that Fur would play a central role in determining the preferable nutrient to be used, either as apo‐Fur through Lrp (Ho et al ., ) in eel serum or as holo‐Fur through unknown pathways in iron‐overloaded human serum as all the glycogen metabolism‐related differentially expressed genes belong to the Fur regulon (Supporting Information Table S4 and Fig. ).…”

“…The models show the main regulators and sensors that would response to the putative external signals in the serum as well as the resultant phenotype. The models are based on our transcriptomic and phenotypic results as well as on data from the literature (Brinkman et al, 2003;Meibom et al, 2005;Krasteva et al, 2010;Shao et al, 2011;Antonova et al, 2012;Kim et al, 2013;Weigel et al, 2015;Pajuelo et al, 2016;Ho et al, 2017). The regulators and sensors are presented as bubbles in red (upregulated in our transcriptome), green (downregulated in our transcriptome) and blue (predicted according to the literature but not found in our transcriptome) surrounded by line purple [belongs to both iron stimulon and Fur regulon ], brown [belongs to the Fur regulon or grey [belongs to the iron stimulon ].…”

“…S2A). The pathogen upregulated lrp, encoding a master regulator for N-compound metabolism, plus multiple genes for organic nitrogen organic compound uptake/ transport/metabolism (Table 1 and Supporting Information Table S2) (Brinkman et al, 2003;Ho et al, 2017). In parallel, genes for regulators/sensors related to nitrogen, phosphorus and nucleoside starvation (cytR) were also differentially expressed in eel serum vs CM9 (Table 1 and Supporting Information Table S2).…”

The Leucine-Responsive Regulatory Protein Lrp Participates in Virulence Regulation Downstream of Small RNA ArcZ in Erwinia amylovora

“…Lrp has also been associated with the expression of virulence-associated genes, especially those in control of fimbriae (38–41), and is an activator of motility (42, 43). Mutants lacking Lrp have reduced virulence in Vibrio vulnificus and Xenorhabdus nematophila (43, 44), but a Δ lrp mutant in Salmonella enterica serovar Typhimurium was fully virulent (45). In E.…”