Transient Transcriptional Activation of the
            <i>Vibrio cholerae</i>
            El Tor Virulence Regulator ToxT in Response to Culture Conditions

Medrano, Ana Imelda; DiRita, Victor J.; Castillo, G. F. Torres del; Sánchez, Jesús R.

doi:10.1128/iai.67.5.2178-2183.1999

Cited by 37 publications

(10 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The relative expression of the master virulence regulator toxT and primary virulence factors ctxA and tcpA was determined by real-time quantitative PCR (RT-qPCR). The 4 h and 5 h time points of in vitro standard AKI conditions were selected to compare relative expression profiles, as toxT expression has been observed to be high at these time points ( 40 ). PDH mutant strains at 4 h exhibited somewhat elevated levels of toxT and tcpA and similar ctxA expression compared to those of the wild-type, with no transcripts detected in the ΔtoxT control, as expected ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…For example, the regulators AphB and OhrR respond to reduced environmental oxygen by activating tcpP expression ( 58 ). Further, decreased oxygen levels under stationary culture conditions stimulates ToxR-TcpP interaction ( 59 ) and activation of toxT transcription ( 40 ). Translating these in vitro results to the context of oxygen distribution in vivo would imply that the anoxic lumen primes V. cholerae for virulence gene expression prior to accessing the more oxygenated host epithelium.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Aerobic Metabolism in Vibrio cholerae Is Required for Population Expansion during Infection

Alst

DiRita

2020

mBio

Self Cite

View full text Add to dashboard Cite

Vibrio cholerae replicates to high cell density in the human small intestine, leading to the diarrheal disease cholera. During infection, V. cholerae senses and responds to environmental signals that govern cellular responses. Spatial localization of V. cholerae within the intestine affects nutrient availability and metabolic pathways required for replicative success. Metabolic processes used by V. cholerae to reach such high cell densities are not fully known. We sought to better define the metabolic traits that contribute to high levels of V. cholerae during infection. By disrupting the pyruvate dehydrogenase (PDH) complex and pyruvate formate-lyase (PFL), we could differentiate aerobic and anaerobic metabolic pathway involvement in V. cholerae proliferation. We demonstrate that oxidative metabolism is a key contributor to the replicative success of V. cholerae in vivo using an infant mouse model in which PDH mutants were attenuated 100-fold relative to the wild type for colonization. Additionally, metabolism of host substrates, including mucin, was determined to support V. cholerae growth in vitro as a sole carbon source, primarily under aerobic growth conditions. Mucin likely contributes to population expansion during human infection as it is a ubiquitous source of carbohydrates. These data highlight oxidative metabolism as important in the intestinal environment and warrant further investigation of how oxygen and other host substrates shape the intestinal landscape that ultimately influences bacterial disease. We conclude from our results that oxidative metabolism of host substrates is a key driver of V. cholerae proliferation during infection, leading to the substantial bacterial burden exhibited in cholera patients. IMPORTANCE Vibrio cholerae remains a challenge in the developing world and incidence of the disease it causes, cholera, is anticipated to increase with rising global temperatures and with emergent, highly infectious strains. At present, the underlying metabolic processes that support V. cholerae growth during infection are less well understood than specific virulence traits, such as production of a toxin or pilus. In this study, we determined that oxidative metabolism of host substrates such as mucin contribute significantly to V. cholerae population expansion in vivo. Identifying metabolic pathways critical for growth can provide avenues for controlling V. cholerae infection and the knowledge may be translatable to other pathogens of the gastrointestinal tract.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Aerobic Metabolism in Vibrio cholerae Is Required for Population Expansion during Infection

Alst

DiRita

2020

mBio

Self Cite

View full text Add to dashboard Cite

show abstract

“…It has been reported that at stationary condition in AKI medium, HCO 3 - could stimulate CT production in O1 El Tor strains by enhancing ToxT activity post-translationally [ 29 , 39 ]. In our present study, inhibition of transcription of ctxA along with tcpA and toxT ( Fig 5A ), suggested that anethole affects the virulence regulatory cascade prior to toxT .…”

Section: Discussionmentioning

confidence: 99%

Suppression of Virulence of Toxigenic Vibrio cholerae by Anethole through the Cyclic AMP (cAMP)-cAMP Receptor Protein Signaling System

et al. 2015

View full text Add to dashboard Cite

Use of natural compounds as antivirulence drugs could be an alternative therapeutic approach to modify the outcome of bacterial infections, particularly in view of growing resistance to available antimicrobials. Here, we show that sub-bactericidal concentration of anethole, a component of sweet fennel seed, could suppress virulence potential in O1 El Tor biotype strains of toxigenic Vibrio cholerae, the causative agent of the ongoing 7th cholera pandemic. The expression of cholera toxin (CT) and toxin coregulated pilus (TCP), the major virulence factors of V. cholerae, is controlled through a regulatory cascade involving activation of ToxT with synergistic coupling interaction of ToxR/ToxS with TcpP/TcpH. We present evidence that anethole inhibits in vitro expression of CT and TCP in a toxT-dependent but toxR/toxS-independent manner and through repression of tcpP/tcpH, by using bead-ELISA, western blotting and quantitative real-time RT-PCR assays. The cyclic AMP (cAMP)-cAMP receptor protein (CRP) is a well-studied global signaling system in bacterial pathogens, and this complex is known to suppress expression of tcpP/tcpH in V. cholerae. We find that anethole influences the virulence regulatory cascade by over-expressing cyaA and crp genes. Moreover, suppression of toxigenic V. cholerae-mediated fluid accumulation in ligated ileum of rabbit by anethole demonstrates its potentiality as an antivirulence drug candidate against the diseases caused by toxigenic V. cholerae. Taken altogether, these results revealing a mechanism of virulence inhibition in V. cholerae by the natural compound anethole, may have relevance in designing antivirulence compounds, particularly against multiple antibiotic resistant bacterial pathogens.

show abstract

“…In addition, ToxR reciprocally regulates the expression of two outer membrane porins, OmpU and OmpT, in response to the nutritional status of the cell [ 36 – 38 ]. Furthermore, unlike tcpP , toxR expression is not altered under conditions that favor the maximal expression of virulence genes in the laboratory [ 39 , 40 ]. In this study, we show that under nutrient limitation at alkaline pH, ToxR levels decrease by a RIP mediated event.…”

Section: Introductionmentioning

confidence: 99%

Proteolysis of Virulence Regulator ToxR Is Associated with Entry of Vibrio cholerae into a Dormant State

et al. 2015

View full text Add to dashboard Cite

Vibrio cholerae O1 is a natural inhabitant of aquatic environments and causes the diarrheal disease, cholera. Two of its primary virulence regulators, TcpP and ToxR, are localized in the inner membrane. TcpP is encoded on the Vibrio Pathogenicity Island (VPI), a horizontally acquired mobile genetic element, and functions primarily in virulence gene regulation. TcpP has been shown to undergo regulated intramembrane proteolysis (RIP) in response to environmental conditions that are unfavorable for virulence gene expression. ToxR is encoded in the ancestral genome and is present in non-pathogenic strains of V. cholerae, indicating it has roles outside of the human host. In this study, we show that ToxR undergoes RIP in V. cholerae in response to nutrient limitation at alkaline pH, a condition that occurs during the stationary phase of growth. This process involves the site-2 protease RseP (YaeL), and is dependent upon the RpoE-mediated periplasmic stress response, as deletion mutants for the genes encoding these two proteins cannot proteolyze ToxR under nutrient limitation at alkaline pH. We determined that the loss of ToxR, genetically or by proteolysis, is associated with entry of V. cholerae into a dormant state in which the bacterium is normally found in the aquatic environment called viable but nonculturable (VBNC). Strains that can proteolyze ToxR, or do not encode it, lose culturability, experience a change in morphology associated with cells in VBNC, yet remain viable under nutrient limitation at alkaline pH. On the other hand, mutant strains that cannot proteolyze ToxR remain culturable and maintain the morphology of cells in an active state of growth. Overall, our findings provide a link between the proteolysis of a virulence regulator and the entry of a pathogen into an environmentally persistent state.

show abstract

Transient Transcriptional Activation of the Vibrio cholerae El Tor Virulence Regulator ToxT in Response to Culture Conditions

Cited by 37 publications

References 36 publications

Aerobic Metabolism in Vibrio cholerae Is Required for Population Expansion during Infection

Aerobic Metabolism in Vibrio cholerae Is Required for Population Expansion during Infection

Suppression of Virulence of Toxigenic Vibrio cholerae by Anethole through the Cyclic AMP (cAMP)-cAMP Receptor Protein Signaling System

Proteolysis of Virulence Regulator ToxR Is Associated with Entry of Vibrio cholerae into a Dormant State

Contact Info

Product

Resources

About