Abstract
Iron is an essential nutrient to support the growth of most bacterial species. However, iron is not easily available to microorganisms infecting mammalian hosts, because it is largely sequestered by iron-binding proteins, such as transferrin or lactoferrin, or complexed to heme. In response to environmental iron stress, Vibrio cholerae produces the siderophore vibriobactin as well as a number of iron-induced outer membrane proteins. Previous data on the role of iron acquisition systems for the intraintestinal growth of mucosal pathogens such as V. cholerae are conflicting. In this report, we isolated mutants of V. cholerae with TnphoA fusions in each of viuA, hutA, and irgA, as well as strains mutant in each pair of these genes and all three simultaneously, to analyze the role of these iron-induced outer membrane protein receptors for in vivo growth of V. cholerae. The fusion between hutA and TnphoA in a single copy on the chromosome allowed the study of in vitro regulation of hutA in response to iron, fur, and irgB; transcription of hutA was tightly iron regulated (70-fold) and dependent on a functional Fur but did not require IrgB. To investigate the effects of mutations in these iron-induced outer membrane proteins on in vivo growth, we inoculated ileal loops in a rabbit model of infection. This avoids exposure of organisms to the potential killing effects of gastric acid, allows several logarithmic increases in growth in the in vivo environment, and facilitates direct comparison of multiple strains in the same animal to avoid any differences between animals. We grew each mutant to be tested in competition with the wild-type strain in the same loop, to provide an internal control. We confirmed that the inocula for these experiments were grown under conditions of iron stress prior to in vivo inoculation, by measuring the alkaline phosphatase activity of the iron-regulated fusion in each strain. The results confirmed that mutation of irgA produced a much more substantial in vivo growth defect than mutation of either hutA or viuA alone. Double mutants of irgA with either viuA or hutA, or the strain mutant in all three genes, showed an in vivo growth defect comparable to the strain mutant in irgA only, suggesting that mutation of irgA was the most relevant for in vivo growth. The strain mutant in both hutA and viuA was also markedly impaired for in vivo growth, suggesting that mutation of both of these iron uptake systems simultaneously can also produce a substantial in vivo growth defect.
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Selected References
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- Butterton J. R., Boyko S. A., Calderwood S. B. Use of the Vibrio cholerae irgA gene as a locus for insertion and expression of heterologous antigens in cholera vaccine strains. Vaccine. 1993 Oct;11(13):1327–1335. doi: 10.1016/0264-410x(93)90103-5. [DOI] [PubMed] [Google Scholar]
- Butterton J. R., Stoebner J. A., Payne S. M., Calderwood S. B. Cloning, sequencing, and transcriptional regulation of viuA, the gene encoding the ferric vibriobactin receptor of Vibrio cholerae. J Bacteriol. 1992 Jun;174(11):3729–3738. doi: 10.1128/jb.174.11.3729-3738.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Camilli A., Beattie D. T., Mekalanos J. J. Use of genetic recombination as a reporter of gene expression. Proc Natl Acad Sci U S A. 1994 Mar 29;91(7):2634–2638. doi: 10.1073/pnas.91.7.2634. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Crosa J. H. Genetics and molecular biology of siderophore-mediated iron transport in bacteria. Microbiol Rev. 1989 Dec;53(4):517–530. doi: 10.1128/mr.53.4.517-530.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Donnenberg M. S., Kaper J. B. Construction of an eae deletion mutant of enteropathogenic Escherichia coli by using a positive-selection suicide vector. Infect Immun. 1991 Dec;59(12):4310–4317. doi: 10.1128/iai.59.12.4310-4317.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goldberg M. B., Boyko S. A., Butterton J. R., Stoebner J. A., Payne S. M., Calderwood S. B. Characterization of a Vibrio cholerae virulence factor homologous to the family of TonB-dependent proteins. Mol Microbiol. 1992 Aug;6(16):2407–2418. doi: 10.1111/j.1365-2958.1992.tb01415.x. [DOI] [PubMed] [Google Scholar]
- Goldberg M. B., Boyko S. A., Calderwood S. B. Positive transcriptional regulation of an iron-regulated virulence gene in Vibrio cholerae. Proc Natl Acad Sci U S A. 1991 Feb 15;88(4):1125–1129. doi: 10.1073/pnas.88.4.1125. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goldberg M. B., Boyko S. A., Calderwood S. B. Transcriptional regulation by iron of a Vibrio cholerae virulence gene and homology of the gene to the Escherichia coli fur system. J Bacteriol. 1990 Dec;172(12):6863–6870. doi: 10.1128/jb.172.12.6863-6870.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goldberg M. B., DiRita V. J., Calderwood S. B. Identification of an iron-regulated virulence determinant in Vibrio cholerae, using TnphoA mutagenesis. Infect Immun. 1990 Jan;58(1):55–60. doi: 10.1128/iai.58.1.55-60.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Griffiths E., Humphreys J. Isolation of enterochelin from the peritoneal washings of guinea pigs lethally infected with Escherichia coli. Infect Immun. 1980 Apr;28(1):286–289. doi: 10.1128/iai.28.1.286-289.1980. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Griffiths E., Stevenson P., Thorpe R., Chart H. Naturally occurring antibodies in human sera that react with the iron-regulated outer membrane proteins of Escherichia coli. Infect Immun. 1985 Mar;47(3):808–813. doi: 10.1128/iai.47.3.808-813.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Griffiths G. L., Sigel S. P., Payne S. M., Neilands J. B. Vibriobactin, a siderophore from Vibrio cholerae. J Biol Chem. 1984 Jan 10;259(1):383–385. [PubMed] [Google Scholar]
- Hanahan D. Studies on transformation of Escherichia coli with plasmids. J Mol Biol. 1983 Jun 5;166(4):557–580. doi: 10.1016/s0022-2836(83)80284-8. [DOI] [PubMed] [Google Scholar]
- Henderson D. P., Payne S. M. Characterization of the Vibrio cholerae outer membrane heme transport protein HutA: sequence of the gene, regulation of expression, and homology to the family of TonB-dependent proteins. J Bacteriol. 1994 Jun;176(11):3269–3277. doi: 10.1128/jb.176.11.3269-3277.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Henderson D. P., Payne S. M. Cloning and characterization of the Vibrio cholerae genes encoding the utilization of iron from haemin and haemoglobin. Mol Microbiol. 1993 Feb;7(3):461–469. doi: 10.1111/j.1365-2958.1993.tb01137.x. [DOI] [PubMed] [Google Scholar]
- Henderson D. P., Payne S. M. Vibrio cholerae iron transport systems: roles of heme and siderophore iron transport in virulence and identification of a gene associated with multiple iron transport systems. Infect Immun. 1994 Nov;62(11):5120–5125. doi: 10.1128/iai.62.11.5120-5125.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jonson G., Svennerholm A. M., Holmgren J. Vibrio cholerae expresses cell surface antigens during intestinal infection which are not expressed during in vitro culture. Infect Immun. 1989 Jun;57(6):1809–1815. doi: 10.1128/iai.57.6.1809-1815.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kammler M., Schön C., Hantke K. Characterization of the ferrous iron uptake system of Escherichia coli. J Bacteriol. 1993 Oct;175(19):6212–6219. doi: 10.1128/jb.175.19.6212-6219.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Litwin C. M., Boyko S. A., Calderwood S. B. Cloning, sequencing, and transcriptional regulation of the Vibrio cholerae fur gene. J Bacteriol. 1992 Mar;174(6):1897–1903. doi: 10.1128/jb.174.6.1897-1903.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Litwin C. M., Calderwood S. B. Analysis of the complexity of gene regulation by fur in Vibrio cholerae. J Bacteriol. 1994 Jan;176(1):240–248. doi: 10.1128/jb.176.1.240-248.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Litwin C. M., Calderwood S. B. Cloning and genetic analysis of the Vibrio vulnificus fur gene and construction of a fur mutant by in vivo marker exchange. J Bacteriol. 1993 Feb;175(3):706–715. doi: 10.1128/jb.175.3.706-715.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Litwin C. M., Calderwood S. B. Role of iron in regulation of virulence genes. Clin Microbiol Rev. 1993 Apr;6(2):137–149. doi: 10.1128/cmr.6.2.137. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mekalanos J. J., Swartz D. J., Pearson G. D., Harford N., Groyne F., de Wilde M. Cholera toxin genes: nucleotide sequence, deletion analysis and vaccine development. Nature. 1983 Dec 8;306(5943):551–557. doi: 10.1038/306551a0. [DOI] [PubMed] [Google Scholar]
- Miller V. L., Mekalanos J. J. A novel suicide vector and its use in construction of insertion mutations: osmoregulation of outer membrane proteins and virulence determinants in Vibrio cholerae requires toxR. J Bacteriol. 1988 Jun;170(6):2575–2583. doi: 10.1128/jb.170.6.2575-2583.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Moore D. G., Yancey R. J., Lankford C. E., Earhart C. F. Bacteriostatic enterochelin-specific immunoglobulin from normal human serum. Infect Immun. 1980 Feb;27(2):418–423. doi: 10.1128/iai.27.2.418-423.1980. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Payne S. M., Finkelstein R. A. Siderophore production by Vibrio cholerae. Infect Immun. 1978 Apr;20(1):310–311. doi: 10.1128/iai.20.1.310-311.1978. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rogers H. J. Iron-Binding Catechols and Virulence in Escherichia coli. Infect Immun. 1973 Mar;7(3):445–456. doi: 10.1128/iai.7.3.445-456.1973. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sciortino C. V., Finkelstein R. A. Vibrio cholerae expresses iron-regulated outer membrane proteins in vivo. Infect Immun. 1983 Dec;42(3):990–996. doi: 10.1128/iai.42.3.990-996.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shand G. H., Anwar H., Kadurugamuwa J., Brown M. R., Silverman S. H., Melling J. In vivo evidence that bacteria in urinary tract infection grow under iron-restricted conditions. Infect Immun. 1985 Apr;48(1):35–39. doi: 10.1128/iai.48.1.35-39.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sigel S. P., Payne S. M. Effect of iron limitation on growth, siderophore production, and expression of outer membrane proteins of Vibrio cholerae. J Bacteriol. 1982 Apr;150(1):148–155. doi: 10.1128/jb.150.1.148-155.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sigel S. P., Stoebner J. A., Payne S. M. Iron-vibriobactin transport system is not required for virulence of Vibrio cholerae. Infect Immun. 1985 Feb;47(2):360–362. doi: 10.1128/iai.47.2.360-362.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stoebner J. A., Butterton J. R., Calderwood S. B., Payne S. M. Identification of the vibriobactin receptor of Vibrio cholerae. J Bacteriol. 1992 May;174(10):3270–3274. doi: 10.1128/jb.174.10.3270-3274.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stoebner J. A., Payne S. M. Iron-regulated hemolysin production and utilization of heme and hemoglobin by Vibrio cholerae. Infect Immun. 1988 Nov;56(11):2891–2895. doi: 10.1128/iai.56.11.2891-2895.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stojiljkovic I., Cobeljic M., Hantke K. Escherichia coli K-12 ferrous iron uptake mutants are impaired in their ability to colonize the mouse intestine. FEMS Microbiol Lett. 1993 Mar 15;108(1):111–115. doi: 10.1111/j.1574-6968.1993.tb06082.x. [DOI] [PubMed] [Google Scholar]
- Tautz D., Renz M. An optimized freeze-squeeze method for the recovery of DNA fragments from agarose gels. Anal Biochem. 1983 Jul 1;132(1):14–19. doi: 10.1016/0003-2697(83)90419-0. [DOI] [PubMed] [Google Scholar]