Subscribe Now Subscribe Today
Research Article

Regulation of toxA by ptxR in the Pseudomonas aeruginosa Strain PA103ΔXR

Rukaia Mohammed Gashgari
Facebook Twitter Digg Reddit Linkedin StumbleUpon E-mail

In this study we have examined ptxR expression in the P. aeruginosa strain (PA103ΔXR) which displays a unique phenotype. The strain was derived from PA103-2R which contains two copies of ptxR and was constructed by the integration of a ptxR plasmid in the PA103 chromosome. PA103ΔXR was isolated by continuously subculturing PA103-2R in antibiotic free media and screening for carbencillin sensitive colonies. Under iron deficient medium, toxA transcription is enhanced significantly. Two peaks of toxA transcription were detected at 4 and 16 h post inoculation. In contrast, toxA transcription in PA103ΔXR was significantly reduced. In iron-sufficient medium toxA transcription was repressed in both PA103 and PA103ΔXR. ptxR regulates toxA expression through the regAB locus. Under iron deficient conditions regA transcription was enhanced after 8 h of growth and reached a peak at 16 h of growth. This was followed by a sharp reduction in regA transcription during 20 and 24 h of growth In contrast, regA transcription in PA103ΔXR was significally reduced at 12 and 16 h of growth. Under high iron conditions, the patterns of regA transcription in PA103 and PA103ΔXR appears to be similar In both strains, it is significantly reduced. The unique phenotype of PA103ΔXR is not due to mutations in either toxA, regAB and ptxR. A plasmid carrying intact toxA, regAB and ptxR failed to complete the defect of PA103ΔXR in exotoxin A synthesis.

Related Articles in ASCI
Similar Articles in this Journal
Search in Google Scholar
View Citation
Report Citation

  How to cite this article:

Rukaia Mohammed Gashgari , 2005. Regulation of toxA by ptxR in the Pseudomonas aeruginosa Strain PA103ΔXR. Journal of Biological Sciences, 5: 186-192.

DOI: 10.3923/jbs.2005.186.192


Bergen, G.A. and J.H. Shelhamer, 1996. Pulmonary infiltrates in the cancer patient. New approaches to an old problem. Infect. Dis. Clin. North Am., 10: 297-325.

Colmer, J.A. and A.N. Hamood, 1998. Characterization of ptxS, a Pseudomonas aeruginosa gene which interferes with the effect of the exotoxin A positive regulatory gene, ptxR. Mol. Gen. Genet., 258: 250-259.

Colmer, J.A. and A.N. Hamood, 2001. Molecular analysis of the Pseudomonas aeruginosa regulatory genes ptxR and ptxS. Can. J. Microbiol., 47: 820-828.

Ditta,G., S. Starfield, D. Corbin and D.R. Helinski, 1980. Board host range DNA cloning system for gram negative bacteria. Construction of a gene bank of Rhizobium meliloti. Proc. Natl. Acad. Sci. USA., 77: 7347-7351.

Friedman, A.M., S.R. Brown, W.J. Buikkema and F.M. Ausubel, 1982. Construction of a braid host cosmid cloning vector and its usage in the genetic analysis of Rhizobium mutants. Genetics, 18: 289-296.

Hamood, A.N., J.A. Griswold and C.M. Duhan, 1996. Production of extracellular virulence factors by Pseudomonas aeruinosa isolates from tracheal, urinary tract and wound infections. Surg. Res., 61: 425-432.

Hamood, A.N., J.A. Griswold and J. Colmer, 1996. Characterization of elastase deficient clinical isolates of Pseudomonas aerginosa. Infect. Immunol., 64: 3154-3160.

Hamood, A.N., M.J. Wick and N.H. Iglewski, 1990. Secretion of toxin A from Psudomonas aeruginosa PAO1, PKA and PA103 by Escherichia coli. Infect. Immunol., 58: 1133-1133.

Laemmli, U.K., 1970. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature, 227: 680-685.
CrossRef  |  Direct Link  |  

Liu, P.V., 1973. Exotoxin A of Pseudomonas aeruginosa. Factors that influence the production of exotoxin A. J. Infect. Dis., 128: 506-513.

Ohman, D.E., J.C. Sadoff and B.H. Iglewski, 1980. Toxin A-deficient mutants of Pseudomonas aerginosa PA103: Isolation and characterization. Infect. Immun., 28: 899-908.

Rumbaugh, K., J.A. Griswold and A.N. Hamood, 1999. Pseudomonas aeruginosa strains obtind from patients with tracheal, urinary tract and wound infection: Variations in virulence factors and virulence genes. J. Hospital Infect., 43: 211-218.

Rumbaugh, K.P., A.N. Hamood and J.A. Griswold, 1999. Anaysis of Pseudomonas aeruginosa clinical isolates for possible variations within the virulence genes exotoxin A and exoenzyme S. J. Syrg. Res., 82: 95-105.

Sawanson, B. and A.N. Hamood, 2000. Autoregulation of Pseudomonas aeruginosa protein PtxS occurs through a specific operator site within the ptxS upstream region. J. Bacteriol., 182: 4366-4371.

Stachel, S.E., G. An, C. Flores and E.W. Nester, 1985. ATn3 lacZ transposon for the random generation of β-galactosidase gene fusions: Application to the analysis of gene expression in Agrobacterium. EMBO J., 4: 891-891.

Storey, D., T. Raivio, D. Frank, M.J. Wick, S. Kaye and B.H. Iglewski, 1991. Effect of regB on expression from the P1 and P2 promoters of the Pseudomonas aeruginosa regAB operon. J. Bacteriol., 173: 6088-6094.

Towbin, H., T. Staehelin and J. Gordon, 1979. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: Procedure and some applications. Proc. Natl. Acad. Sci. USA., 76: 4350-4354.
PubMed  |  Direct Link  |  

©  2020 Science Alert. All Rights Reserved