Pseudomonas aeruginosa mutants altered in their sensitivity to the effect of iron on toxin A or elastase yields

Sokol, Pamela A.; Cox, C D; Iglewski, B H

doi:10.1128/jb.151.2.783-787.1982

Cited by 48 publications

(16 citation statements)

References 17 publications

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“…Thus, it appears that, for sodA , the QS regulatory system is integrated with iron-sensitive circuitry that activates transcription of the operon regardless of growth phase (Hassett et al, 1996). We note that this is also consistent with the effects of iron availability on production of the P. aeruginosa virulence factors elastase, exotoxin A and pyoverdine (Sokol et al, 1982).…”

Section: Mn-sodsupporting

confidence: 76%

Quorum sensing in Pseudomonas aeruginosa controls expression of catalase and superoxide dismutase genes and mediates biofilm susceptibility to hydrogen peroxide

Hassett

Elkins

et al. 1999

Molecular Microbiology

373

278

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SummaryQuorum sensing (QS) governs the production of virulence factors and the architecture and sodium dodecyl sulphate (SDS) resistance of bio®lm-grown Pseudomonas aeruginosa. P. aeruginosa QS requires two transcriptional activator proteins known as LasR and RhlR and their cognate autoinducers PAI-1 (N-(3-oxododecanoyl)-L-homoserine lactone) and PAI-2 (Nbutyryl-L-homoserine lactone) respectively. This study provides evidence of QS control of genes essential for relieving oxidative stress. Mutants devoid of one or both autoinducers were more sensitive to hydrogen peroxide and phenazine methosulphate, and some PAI mutant strains also demonstrated decreased expression of two superoxide dismutases (SODs), Mn-SOD and Fe-SOD, and the major catalase, KatA. The expression of sodA (encoding Mn-SOD) was particularly dependent on PAI-1, whereas the in¯uence of autoinducers on Fe-SOD and KatA levels was also apparent but not to the degree observed with Mn-SOD. b-Galactosidase reporter fusion results were in agreement with these ®ndings. Also, the addition of both PAIs to suspensions of the PAI-1/2-de®cient double mutant partially restored KatA activity, while the addition of PAI-1 only was suf®cient for full restoration of Mn-SOD activity. In bio®lm studies, catalase activity in wild-type bacteria was signi®cantly reduced relative to planktonic bacteria; catalase activity in the PAI mutants was reduced even further and consistent with relative differences observed between each strain grown planktonically. While wild-type and mutant bio®lms contained less catalase activity, they were more resistant to hydrogen peroxide treatment than their respective planktonic counterparts. Also, while catalase was implicated as an important factor in bio®lm resistance to hydrogen peroxide insult, other unknown factors seemed potentially important, as PAI mutant bio®lm sensitivity appeared not to be incrementally correlated to catalase levels.

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Section: Mn-sodsupporting

confidence: 76%

Quorum sensing in Pseudomonas aeruginosa controls expression of catalase and superoxide dismutase genes and mediates biofilm susceptibility to hydrogen peroxide

Hassett

Elkins

et al. 1999

Molecular Microbiology

373

278

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“…S, fyp/i/mur/iym might use the limitation of free iron as a signal for induction of virulence genes. It has been shown that haemolysin induction in Listeria monocytogenes (Cowart, 1987) or exotoxin A induction in Pseudomonas aeruginosa (Sokol et al,. 1982) are regulated by free iron.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the micro‐environment of Salmonella typhimurium–containing vacuoles within MDCK epithelial cells

Portillo

Foster

Maguire

et al. 1992

Molecular Microbiology

167

102

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Salmonella typhimurium has the capacity to enter into and multiply within epithelial cells. During the entire intracellular stage, bacteria are enclosed within a vacuole. To characterize the micro-environment of the bacteria-containing vacuoles, we have used a new method to measure the expression levels of several S. typhimurium genes in intracellular bacteria within Madin-Darby canine kidney (MDCK) epithelial cells. Our study was based on the determination of beta-galactosidase activity derived from lacZ transcriptional fusions using the highly sensitive substrate fluorescein-di-beta-D-galactoside (FDG). Expression of the iroA and mgtB genes (induced by Fe2+ and Mg2+ limitation respectively), and cadA (induced by pH 6.0 in the presence of lysine, with enhanced expression under anaerobiosis) were characterized at different post-infection times. High intracellular expression levels were detected for the iroA and mgtB genes, suggesting that the concentrations of free Fe2+ and Mg2+ in the vacuole may be low. cadA activity was detected only at early post-infection times (4 h), suggesting that the vacuole may have a mild-acidic pH, and oxygen and lysine present at this time. Globally, the results reported indicate that the use of a highly sensitive beta-galactosidase substrate can provide information about the micro-environment within which an intracellular pathogen, such as S. typhimurium, resides.

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“…Pyochelin is a salicylic acid-substituted cysteinyl peptide siderophore [3]. P. aeruginosa and P. fluorescens also produce pyoverdin which has been shown to have siderophore activity [4,5]. A third mechanism for iron transport from ferric, citrate has also been described in P. aeruginosa [6].…”

Section: Introductionmentioning

confidence: 99%

Production of the ferripyochelin outer membrane receptor by Pseudomonas species

Sokol

1984

FEMS Microbiology Letters

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Production of pyochelin by Pseudomonas species was measured in ethyl acetate extracts of culture supernatants. Pyochelin was purified by paper chromatography, followed by two-dimensional, thin-layer chromatography. Strains of P. cepacia, P. multivorans, and P. fluorescens produced pyochelin, while P. stutzeri, P. putida and P. maltophila were negative for pyochelin production. Outer membranes prepared from these strains had a protein of M r 14000 which was shown to bind [ 59 Fe]pyochelin.

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Pseudomonas aeruginosa mutants altered in their sensitivity to the effect of iron on toxin A or elastase yields

Cited by 48 publications

References 17 publications

Quorum sensing in Pseudomonas aeruginosa controls expression of catalase and superoxide dismutase genes and mediates biofilm susceptibility to hydrogen peroxide

Quorum sensing in Pseudomonas aeruginosa controls expression of catalase and superoxide dismutase genes and mediates biofilm susceptibility to hydrogen peroxide

Characterization of the micro‐environment of Salmonella typhimurium–containing vacuoles within MDCK epithelial cells

Production of the ferripyochelin outer membrane receptor by Pseudomonas species

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