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. 1995 Jan;63(1):154–159. doi: 10.1128/iai.63.1.154-159.1995

Heat stress alters the virulence of a rifampin-resistant mutant of Francisella tularensis LVS.

N B Bhatnagar 1, K L Elkins 1, A H Fortier 1
PMCID: PMC172972  PMID: 7806352

Abstract

We have studied the stress response of a rifampin-resistant mutant of Francisella tularensis LVS. This mutant, Rif 7, was avirulent with an intraperitoneally administered 50% lethal dose greater than 10(7) CFU in a murine model of infection. Exposure of Rif 7 to heat stress for 5 h in vitro resulted in a 2-log decrease in its 50% lethal dose (P < 0.02). The increase in virulence was dependent on the time of exposure to high temperature and was maximal at 5 h. Envelope preparations from heat-stressed cells showed increased levels of several proteins. Notable among these were polypeptides with approximate molecular masses of 16, 60, and 75 kDa. Increases in both virulence and envelope protein levels were reversed when heat-treated cells were subsequently grown at 37 degrees C. Inhibition of protein synthesis by actinomycin D during heat stress blocked the increase in virulence of Rif 7. Cell-free media from the heat-stressed Rif 7 reacted with the whole spectrum of bacterial proteins were not toxic to mice. Hyperimmune serum against Rif 7 reacted with the whole spectrum of bacterial proteins in Western blots (immunoblots), although its reaction with 34- and 45-kDa proteins and two 60- and 75-kDa proteins upregulated during heat stress was weak. Other stress conditions, low iron and low pH, caused similar increases in the virulence of Rif 7. However, examination of the protein profile did not reveal any major common polypeptides induced by different stresses. Heat-treated Rif 7 bacteria were fully able to replicate in macrophages in vitro and in the host tissues, even though heat treatment only partially restored virulence.

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Selected References

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  1. Abshire K. Z., Neidhardt F. C. Growth rate paradox of Salmonella typhimurium within host macrophages. J Bacteriol. 1993 Jun;175(12):3744–3748. doi: 10.1128/jb.175.12.3744-3748.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Abu Kwaik Y., Eisenstein B. I., Engleberg N. C. Phenotypic modulation by Legionella pneumophila upon infection of macrophages. Infect Immun. 1993 Apr;61(4):1320–1329. doi: 10.1128/iai.61.4.1320-1329.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bhatnagar N., Getachew E., Straley S., Williams J., Meltzer M., Fortier A. Reduced virulence of rifampicin-resistant mutants of Francisella tularensis. J Infect Dis. 1994 Oct;170(4):841–847. doi: 10.1093/infdis/170.4.841. [DOI] [PubMed] [Google Scholar]
  4. Brener D., DeVoe I. W., Holbein B. E. Increased virulence of Neisseria meningitidis after in vitro iron-limited growth at low pH. Infect Immun. 1981 Jul;33(1):59–66. doi: 10.1128/iai.33.1.59-66.1981. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Buchmeier N. A., Heffron F. Induction of Salmonella stress proteins upon infection of macrophages. Science. 1990 May 11;248(4956):730–732. doi: 10.1126/science.1970672. [DOI] [PubMed] [Google Scholar]
  6. Burns D. L., Gould-Kostka J. L., Kessel M., Arciniega J. L. Purification and immunological characterization of a GroEL-like protein from Bordetella pertussis. Infect Immun. 1991 Apr;59(4):1417–1422. doi: 10.1128/iai.59.4.1417-1422.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. CHAMBERLAIN R. E. EVALUATION OF LIVE TULAREMIA VACCINE PREPARED IN A CHEMICALLY DEFINED MEDIUM. Appl Microbiol. 1965 Mar;13:232–235. doi: 10.1128/am.13.2.232-235.1965. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. EIGELSBACH H. T., DOWNS C. M. Prophylactic effectiveness of live and killed tularemia vaccines. I. Production of vaccine and evaluation in the white mouse and guinea pig. J Immunol. 1961 Oct;87:415–425. [PubMed] [Google Scholar]
  9. Fields P. I., Swanson R. V., Haidaris C. G., Heffron F. Mutants of Salmonella typhimurium that cannot survive within the macrophage are avirulent. Proc Natl Acad Sci U S A. 1986 Jul;83(14):5189–5193. doi: 10.1073/pnas.83.14.5189. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Fortier A. H., Polsinelli T., Green S. J., Nacy C. A. Activation of macrophages for destruction of Francisella tularensis: identification of cytokines, effector cells, and effector molecules. Infect Immun. 1992 Mar;60(3):817–825. doi: 10.1128/iai.60.3.817-825.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Fortier A. H., Slayter M. V., Ziemba R., Meltzer M. S., Nacy C. A. Live vaccine strain of Francisella tularensis: infection and immunity in mice. Infect Immun. 1991 Sep;59(9):2922–2928. doi: 10.1128/iai.59.9.2922-2928.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Horwitz M. A. Characterization of avirulent mutant Legionella pneumophila that survive but do not multiply within human monocytes. J Exp Med. 1987 Nov 1;166(5):1310–1328. doi: 10.1084/jem.166.5.1310. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Johnson K., Charles I., Dougan G., Pickard D., O'Gaora P., Costa G., Ali T., Miller I., Hormaeche C. The role of a stress-response protein in Salmonella typhimurium virulence. Mol Microbiol. 1991 Feb;5(2):401–407. doi: 10.1111/j.1365-2958.1991.tb02122.x. [DOI] [PubMed] [Google Scholar]
  14. Keath E. J., Painter A. A., Kobayashi G. S., Medoff G. Variable expression of a yeast-phase-specific gene in Histoplasma capsulatum strains differing in thermotolerance and virulence. Infect Immun. 1989 May;57(5):1384–1390. doi: 10.1128/iai.57.5.1384-1390.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
  16. Lathigra R. B., Butcher P. D., Garbe T. R., Young D. B. Heat shock proteins as virulence factors of pathogens. Curr Top Microbiol Immunol. 1991;167:125–143. doi: 10.1007/978-3-642-75875-1_8. [DOI] [PubMed] [Google Scholar]
  17. Maurelli A. T. Temperature regulation of virulence genes in pathogenic bacteria: a general strategy for human pathogens? Microb Pathog. 1989 Jul;7(1):1–10. doi: 10.1016/0882-4010(89)90106-x. [DOI] [PubMed] [Google Scholar]
  18. Mekalanos J. J. Environmental signals controlling expression of virulence determinants in bacteria. J Bacteriol. 1992 Jan;174(1):1–7. doi: 10.1128/jb.174.1.1-7.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Miller J. F., Mekalanos J. J., Falkow S. Coordinate regulation and sensory transduction in the control of bacterial virulence. Science. 1989 Feb 17;243(4893):916–922. doi: 10.1126/science.2537530. [DOI] [PubMed] [Google Scholar]
  20. Miller S. I., Kukral A. M., Mekalanos J. J. A two-component regulatory system (phoP phoQ) controls Salmonella typhimurium virulence. Proc Natl Acad Sci U S A. 1989 Jul;86(13):5054–5058. doi: 10.1073/pnas.86.13.5054. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Parsot C., Mekalanos J. J. Expression of ToxR, the transcriptional activator of the virulence factors in Vibrio cholerae, is modulated by the heat shock response. Proc Natl Acad Sci U S A. 1990 Dec;87(24):9898–9902. doi: 10.1073/pnas.87.24.9898. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Tärnvik A. Nature of protective immunity to Francisella tularensis. Rev Infect Dis. 1989 May-Jun;11(3):440–451. [PubMed] [Google Scholar]
  23. Valone S. E., Chikami G. K., Miller V. L. Stress induction of the virulence proteins (SpvA, -B, and -C) from native plasmid pSDL2 of Salmonella dublin. Infect Immun. 1993 Feb;61(2):705–713. doi: 10.1128/iai.61.2.705-713.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]

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