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Published online ahead of print on 23 April 2009 as doi:10.1099/mic.0.028373-0
Microbiology 2009;155:2265.

Microbiology (2009), DOI 10.1099/mic.0.028373-0
© 2009 Society for General Microbiology
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Microbiology 0 (2009), mic.0.028373; DOI  10.1099/mic.0.028373-0
© 2009 Society for General Microbiology

The role of Vfr in regulating exotoxin A production by Pseudomonas aeruginosa

Marko Davinic1, Nancy L. Carty1, Jane A. Colmer-Hamood2, Michael San Francisco1 and Abdul N. Hamood2,3

1 Texas Tech University;
2 Texas Tech University Health Sciences Center

ABSTRACT

Pseudomonas aeruginosa exotoxin A (ETA) production depends on the virulence factor regulator Vfr. Recent evidence indicates that the P. aeruginosa iron-starvation sigma factor PvdS also enhances ETA production through the ETA regulatory gene regA. Mutants defective in vfr, regA, and pvdS; plasmids that individually overexpress these genes; and lacZ transcriptional/translational fusion plasmids were utilized to examine the relationship between vfr, regA, and pvdS in regulating P. aeruginosa ETA production. ETA concentration and regA expression were significantly reduced in PAO{Delta}vfr, but pvdS expression was not affected. Overexpression of Vfr produced a limited increase in ETA production in PAO{Delta}pvdS but not PAO{Delta}regA. Additionally, overexpression of either RegA or PvdS did not enhance ETA production in PAO{Delta}vfr. RT-PCR analysis showed that iron did not affect the accumulation of vfr mRNA in PAO1. These results suggest that: (1) Vfr enhances toxA expression in PAO1 both directly and indirectly through regA but not through pvdS; (2) vfr expression is not regulated by iron; and (3) both Vfr and PvdS cooperate in the presence of RegA to achieve a maximum level of toxA expression.

3 E-mail: abdul.hamood{at}ttuhsc.edu






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