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Unusual Properties of Catalase A (KatA) of Pseudomonas aeruginosa PA14 Are Associated with Its Biofilm Peroxide Resistance

Department of Life Science, Sogang University, Seoul 121-742, Republic of Korea

Received 30 September 2007/ Accepted 17 December 2007

Pseudomonas aeruginosa is a ubiquitous environmental bacterium whose major catalase (KatA) is highly stable, extracellularly present, and required for full virulence as well as for peroxide resistance in planktonic and biofilm states. Here, we dismantled the function of P. aeruginosa KatA (KatA_Pa) by comparing its properties with those of two evolutionarily related (clade 3 monofunctional) catalases from Bacillus subtilis (KatA_Bs) and Streptomyces coelicolor (CatA_Sc). We switched the coding region for KatA_Pa with those for KatA_Bs and CatA_Sc, expressed the catalases under the potential katA-regulatory elements in a P. aeruginosa PA14 katA mutant, and verified their comparable protein levels by Western blot analysis. The activities of KatA_Bs and CatA_Sc, however, were less than 40% of the KatA_Pa activity, suggestive of the difference in intrinsic catalatic activity or efficiency for posttranslational activity modulation in P. aeruginosa. Furthermore, KatA_Bs and CatA_Sc were relatively susceptible to proteinase K, whereas KatA_Pa was highly stable upon proteinase K treatment. As well, KatA_Bs and CatA_Sc were undetectable in the extracellular milieu. Nevertheless, katA_Bs and catA_Sc fully rescued the peroxide sensitivity and osmosensitivity of the katA mutant, respectively. Both catalase genes rescued the attenuated virulence of the katA mutant in mouse acute infection and Drosophila melanogaster models. However, the peroxide susceptibility of the katA mutant in a biofilm growth state was rescued by neither katA_Bs nor catA_Sc. Based on these results, we propose that the P. aeruginosa KatA is highly stable compared to the two major catalases from gram-positive bacteria and that its unique properties involving metastability and extracellular presence may contribute to the peroxide resistance of P. aeruginosa biofilm and presumably to chronic infections.

Published ahead of print on 28 December 2007.