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J. Bacteriol. doi:10.1128/JB.01580-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

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, Korea

^* To whom correspondence should be addressed. Email: youhee{at}sogang.ac.kr.

	Abstract

Pseudomonas aeruginosa is a ubiquitous environmental bacterium, whose major catalase (KatA) is highly stable, extracellularly present and required for full virulence as well as peroxide resistance in planktonic and biofilm states. Here, we dismantled the function of KatA (PA-KatA) by comparing its properties with those of two evolutionarily related (clade 3 monofunctional) catalases from Bacillus subtilis (BS-KatA) and Streptomyces coelicolor (SC-CatA). We switched the coding region of PA-KatA with BS-KatA and SC-CatA and expressed the catalases under the potential katA-regulatory elements in P. aeruginosa PA14 katA mutant and verified their comparable protein levels by Western blot analysis. The activities of BS-KatA and SC-CatA, however, were less than 40% of the PA-KatA activity, suggestive of the difference in intrinsic catalatic activity or efficiency for posttranslational activity modulation in P. aeruginosa. Furthermore, BS-KatA and SC-CatA were relatively susceptible to proteinase K, whereas PA-KatA was highly stable upon proteinase K treatment. As well, BS-KatA and SC-CatA were undetectable in the extracellular milieu. Nevertheless, BS-KatA and SC-CatA fully rescued the peroxide sensitivity and osmosensitivity of the katA mutant, respectively. Both catalases 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 biofilm growth state was rescued by neither BS-KatA nor SC-CatA. 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 the chronic infections.