Genetic analysis of the cholera toxin-positive regulatory gene toxR

Miller, Virginia L; Mekalanos, John J.

doi:10.1128/jb.163.2.580-585.1985

Cited by 63 publications

(11 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, none of the classical strains tested produced less TcpA during growth in vivo compared with growth at 30°C under conditions that promote ToxR expression in vitro. Because classical and El Tor strains (also the strains scored only as weakly positive in Table 1) produced similar, high levels of CT in vivo, suggesting good expression of ToxR in both biotypes under in vivo conditions, other regulatory proteins in addition to ToxR (and ToxT) may be involved in TcpA expression in El Tor strains (4,21). In addition, El Tor strains may lack proteins-factors needed for assembly and/or membrane translocation of TcpA (33 despite substantial TcpA production is a reverse analogy to the essential absence of El Tor-associated mannose-sensitive hemagglutinin pili on classical strains, although the mannose-sensitive hemagglutinin pilin protein is found intracellularly in bacteria of both biotypes (14).…”

Section: Discussionmentioning

confidence: 99%

Analysis of expression of toxin-coregulated pili in classical and El Tor Vibrio cholerae O1 in vitro and in vivo

1992

View full text Add to dashboard Cite

The expression of toxin-coregulated pili (TCP) and their structural subunit TcpA was compared in 20 strains of Vibrio cholerae of the classical and El Tor biotypes. Bacteria were isolated from the intestines of rabbits with experimental cholera and compared with the same strains grown under optimal TCP expression conditions in vitro. Immunoblotting revealed that TcpA production was induced in both biotypes after vibrios entered the intestinal milieu; TcpA-negative inocula gave rise to TcpA-positive vibrios after multiplication in the gut. The levels of TcpA expressed during growth in the intestine were, for most strains, comparable to those attained under optimal growth conditions in vitro. Of 11 classical strains tested, 10 expressed TCP antigen on the bacterial surface at levels comparable to or exceeding those seen after growth in vitro as determined by an inhibition enzyme-linked immunosorbent assay. In contrast, only one of the nine El Tor strains studied produced detectable amounts of TCP surface antigen in vivo and no fimbriae or surface antigen reacting with anti-TCP serum was found on El Tor vibrios from human cholera stools. Distinct TCP fimbriae were observed by immunoelectron microscopy on classical-biotype vibrios grown either in rabbit intestines or in vitro but were not detected on El Tor vibrios. The results show that TCP is expressed on V. cholerae O1 of the classical biotype but not on V. cholerae O1 of the El Tor biotype in the intestines of rabbits with experimental cholera infection.

show abstract

Section: Discussionmentioning

confidence: 99%

Analysis of expression of toxin-coregulated pili in classical and El Tor Vibrio cholerae O1 in vitro and in vivo

1992

View full text Add to dashboard Cite

show abstract

“…It is possible that iron could regulate expression of ETA via the classical repressoroperator model, as has been proposed for regulation of diphtheria toxin by iron (20), or that a positive regulatory * Corresponding author. mechanism may be involved in regulating the expression of ETA, as has been recently described for cholera toxin (26,27). It has also been suggested that the big differences in the absolute amounts of ETA produced in vitro by different strains could be the result of the duplication of the ETA gene in some strains.…”

mentioning

confidence: 87%

Molecular studies of Pseudomonas exotoxin A gene

Vasil¹,

Chamberlain²,

Grant³

1986

Infect Immun

View full text Add to dashboard Cite

A 2.7-kilobase DNA fragment carrying the entire exotoxin A (ETA) structural gene was divided into three nonoverlapping probes. Two probes covering the ETA structural gene were used in colony hybridization experiments to determine whether sequences homologous to the ETA gene could be detected in genera other than Pseudomonas or in Pseudomonas species other than Pseudomonas aeruginosa. The majority of strains examined other than the P. aeruginosa strains failed to react in the colony hybridization assays. Some Pseudomonas spp. other than P. aeruginosa and some Bordetella spp. did react in colony hybridization assays with the probes. However, additional studies in which we used Southern hybridization methods indicated that these reactions were apparently nonspecific and that the ETA gene is limited to P. aeruginosa. Studies in which we used all three ETA-related probes in Southern hybridization experiments to analyze the ETA gene and surrounding sequences in P. aeruginosa strains isolated from diverse sources revealed the following: (i) the incidence of the ETA gene in P. aeruginosa is-95%; (ii) there are strains which have been isolated from human infections that do not carry the ETA structural gene; (iii) there is a maximum of one copy of the ETA gene per genome in any given strain; (iv) sequences within and 4 to 5 kilobases downstream of the ETA structural gene appear to be well conserved in different strains of P. aeruginosa; and (v) in contrast, sequences immediately upstream of the ETA structural gene are considerably rearranged from strain to strain. A multicopy plasmid carrying the entire cloned ETA gene was transferred to a tox-P. aeruginosa strain. This strain synthesized and secreted mature, full-length ETA, but the amount produced was small considering the multicopy nature of the plasmid. Synthesis of toxin in this strain was only minimally affected by iron. Our data suggest that the synthesis of ETA is positively regulated. Finally, we found that the presence of the ETA gene is independent of the ability of P. aeruginosa to produce several other recognized virulence factors, supporting the concept of the multifactorial nature of P. aeruginosa virulence.

show abstract

“…Miller et ai (1987) showed that a toxR mutant of V. choleraethaX produced no cholera toxin under any growth conditions could be complemented by toxR expressed from a plasmid, pVM7, on which toxR was apparently expressed from a piasmid promoter, and not the normal toxf? promoter (Miller, 1985). in V. cholerae toxf?…”

Section: Toxr Controls a Virulence Regulon In V Choleraementioning

confidence: 99%

Co‐ordinate expression of virulence genes by ToxR in Vibrio cholerae

DiRita

1992

Molecular Microbiology

222

140

View full text Add to dashboard Cite

Evolution of complex regulatory pathways that control virulence factor expression in pathogenic bacteria indicates the importance to these organisms of being able to distinguish time and place. In the human intestinal pathogen Vibrio cholerae, control over many virulence genes identified to date is the responsibility of the ToxR protein. ToxR, in conjunction with a second regulatory protein called ToxS, directly activates the genes encoding the cholera toxin; other ToxR regulated genes are not activated directly by ToxR. For some of these genes, ToxR manifests its control through another activator called ToxT. Expression of toxT, which encodes a member of the AraC family of bacterial transcriptional activators, is ToxR dependent and is modulated by in vitro growth conditions that modulate expression of the ToxR virulence regulon. Thus, as in other regulatory circuits, co-ordinate expression of several genes in V. cholerae results from the activity of a cascading system of regulatory factors.

show abstract

Genetic analysis of the cholera toxin-positive regulatory gene toxR

Cited by 63 publications

References 15 publications

Analysis of expression of toxin-coregulated pili in classical and El Tor Vibrio cholerae O1 in vitro and in vivo

Analysis of expression of toxin-coregulated pili in classical and El Tor Vibrio cholerae O1 in vitro and in vivo

Molecular studies of Pseudomonas exotoxin A gene

Co‐ordinate expression of virulence genes by ToxR in Vibrio cholerae

Contact Info

Product

Resources

About