1887

Abstract

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

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2009-07-01
2021-10-26
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