Pseudomonas aeruginosa is an opportunistic pathogen known to be resistant to different classes of antibiotics and disinfectants. P. aeruginosa also displays a certain degree of tolerance to photodynamic therapy (PDT), an alternative antimicrobial approach exploiting a photo-oxidative stress induced by exogenous photosensitizers and visible light. In order to evaluate if P. aeruginosa pigments can contribute to its relative tolerance to PDT, we analysed the response to this treatment of isogenic transposon mutants of P. aeruginosa PAO1 with altered pigmentation. In general, in the presence of pigments a higher tolerance to PDT induced photooxidative stress was observed. Hyperproduction of pyomelanine makes the cells much more tolerant to stress caused by either radicals or singlet oxygen generated by different PSs upon photoactivation. Phenazines, pyocyanine and phenazine-1- carboxylic acid (PCA), produced in different amounts depending on the cultural conditions, are able to counteract both types of PDT elicited ROS. Hyperproduction of pyoverdine, caused by a mutation in a quorum-sensing gene, rendered P. aeruginosa more tolerant to a photosensitizer that generates mainly singlet oxygen, although in this case the observed tolerance to photo-oxidative stress cannot be exclusively attributed to the presence of the pigment.
Pigments influence the tolerance of Pseudomonas aeruginosa PAO1 to photodynamically induced oxidative stress
ORLANDI, VIVIANA TERESA;BOLOGNESE, FABRIZIO;CHIODAROLI, LUCA;BARBIERI, PAOLA
2015-01-01
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen known to be resistant to different classes of antibiotics and disinfectants. P. aeruginosa also displays a certain degree of tolerance to photodynamic therapy (PDT), an alternative antimicrobial approach exploiting a photo-oxidative stress induced by exogenous photosensitizers and visible light. In order to evaluate if P. aeruginosa pigments can contribute to its relative tolerance to PDT, we analysed the response to this treatment of isogenic transposon mutants of P. aeruginosa PAO1 with altered pigmentation. In general, in the presence of pigments a higher tolerance to PDT induced photooxidative stress was observed. Hyperproduction of pyomelanine makes the cells much more tolerant to stress caused by either radicals or singlet oxygen generated by different PSs upon photoactivation. Phenazines, pyocyanine and phenazine-1- carboxylic acid (PCA), produced in different amounts depending on the cultural conditions, are able to counteract both types of PDT elicited ROS. Hyperproduction of pyoverdine, caused by a mutation in a quorum-sensing gene, rendered P. aeruginosa more tolerant to a photosensitizer that generates mainly singlet oxygen, although in this case the observed tolerance to photo-oxidative stress cannot be exclusively attributed to the presence of the pigment.
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