Response of Pseudomonas aeruginosa to pyocyanin: mechanisms of resistance, antioxidant defenses, and demonstration of a manganese-cofactored superoxide dismutase

Abstract

Pseudomonas aeruginosa produces a blue pigment, pyocyanin. Pyocyanin is a redox-active phenazine compound that kills mammalian and bacterial cells through the generation of reactive oxygen intermediates. We examined the mechanisms by which P. aeruginosa resists pyocyanin. [14C]pyocyanin was taken up by both Escherichia coli and P. aeruginosa, though more slowly by the latter. Cyanide-insensitive respiration, used as an indicator of intracellular superoxide and/or hydrogen peroxide production, was 50-fold less in pyocyanintreated P. aeruginosa than in E. coli. P. aeruginosa showed less cyanide-insensitive respiration than E. coli upon exposure to other redox-active compounds (paraquat, streptonigrin, and plumbagin). Electron paramagnetic resonance spectrometry and spin trapping showed that P. aeruginosa generated less pyocyanin radical and superoxide than E. coli. Cell extracts from E. coli contained an NADPH:pyocyanin oxidoreductase which increased the rate of reduction of pyocyanin by NADPH. Conversely, cell extracts from P. aeruginosa contained no NADPH:pyocyanin oxidoreductase activity and actually decreased the rate of pyocyanin-mediated NADPH oxidation. Antioxidant defenses could also reduce the sensitivity of P. aeruginosa to pyocyanin. Under culture conditions of limited phosphate, both pyocyanin production and catalase activity were enhanced. Superoxide dismutase activity was also increased under low-phosphate conditions. When cells were grown in a high-phosphate succinate medium, P. aeruginosa formed a previously described iron-superoxide dismutase as well as a manganese-cofactored superoxide dismutase. These results demonstrate that P. aeruginosa resists pyocyanin because of limited redox cycling of this compound and that under conditions favoring pyocyanin production, catalase and superoxide dismutase activities increase.

Attenuation of Pseudomonas aeruginosa virulence by marine invertebrate-derived Streptomyces sp.

“…Pyocyanin is a blue-coloured pigment produced by Ps. aeruginosa found in the sputum of patients suffering from cystic fibrosis, suggesting its role in pulmonary tissue damage observed with chronic lung infections (Hassett et al 1992). The pigment also confers a selective advantage to Ps.…”

The alternative sigma factor RpoN regulates the quorum sensing generhlIinPseudomonas aeruginosa

“…Elastase was measured as previously described [21]. Cultures used for pyocyanin assays were grown in LPSM medium as the low phosphate increases pyocyanin expression [15]. Pyocyanin was measured as described [22].…”

7-fluoroindole as an antivirulence compound against Pseudomonas aeruginosa

“…Pseudomonas aeruginosa is an opportunistic human pathogen that readily develops antibiotic resistance and it is a lethal pathogen of particular importance in cystic fibrosis patients (Stover et al, 2000). The bacterium produces a variety of virulence factors, such as Pseudomonas quinolone signal (PQS) (Mashburn & Whiteley, 2005), pyocyanin (Hassett et al, 1992), rhamnolipids (Zulianello et al, 2006), elastase (Pearson et al, 1997) and two endogenous siderophores, pyoverdine and pyochelin (Michel et al, 2005), which are involved in chronic infection (Ben Haj Khalifa et al, 2011). Pseudomonas aeruginosa also produces adhesion factors, exotoxin A, phospholipase C for hemolysis, and exoenzyme S, which are involved in acute infection (Ben Haj Khalifa et al, 2011).…”