Genome-wide transcriptional profiling of the steady-state response of Pseudomonas aeruginosa to hydrogen peroxide

Abstract

The steady-state response of Pseudomonas aeruginosa to the oxidative-stress-generating agent hydrogen peroxide was analyzed by PAO1 transcriptome profiling. In total, 694, 411, and 237 genes were upregulated and 668, 576, and 468 genes were downregulated in P. aeruginosa strains TB, 892, and PAO1, respectively. The expression profiles of the two variants of the TB clone were significantly more related to each other than the expression profile of either strain was to that of PAO1. Exposure to H(2)O(2) activated by more than 10-fold the expression of the cyoABCD operon, which is key for aerobic respiration, and of oxidative-stress response elements such as the catalase KatB, the alkyl hydroperoxide reductase AhpF, and the thioredoxin reductase 2 operon. Genes for iron and sulfur homeostasis were upregulated. Most enzymes necessary for the conversion of amino acids into the citric acid cycle were globally downregulated at the transcriptional level. Nitrate respiration and arginine fermentation were shut off in the clone TB strains and attenuated in the PAO strain. The transcriptional profiles indicate that the two clone TB strains are more proficient in coping with H(2)O(2)-mediated oxidative stress than the reference strain PAO. According to this data, we recommend study of the transcriptome of strain PAO1 in parallel with those of at least two strains of another clone in order to differentiate common responses from clone- and strain-specific responses and to minimize overinterpretations of microarray data.

FIG. 1.

Differential gene expression in response to hydrogen peroxide in the analyzed P. aeruginosa strains PAO1, 892, and TB. The number of genes showing increased or decreased expression and their levels of induction or repression are indicated.

FIG. 2.

PAO1 genes with significantly changed expression levels in hydrogen peroxide-treated P. aeruginosa TB, 892, and PAO1. Genes that were found to be up- or downregulated in two or three strains are indicated in the intersections.

FIG. 3.

Global comparison of the genes identified to be differentially regulated upon exposure to hydrogen peroxide by Palma et al. (36) and in this study.