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J. Bacteriol. doi:10.1128/JB.01262-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

ColRS two-component system regulates membrane functions and protects Pseudomonas putida against phenol

Paula Ann Kivistik, Marta Putrin, Külliki Püvi, Heili Ilves, Maia Kivisaar, and Rita Hõrak^*

Estonian Biocentre and Institute of Molecular and Cell Biology, Tartu University, 51010 Tartu, Estonia

^* To whom correspondence should be addressed. Email: rhorak{at}ebc.ee.

	Abstract

As reported, two-component system ColRS is involved in two completely different processes. It facilitates the root colonization ability of Pseudomonas fluorescens, and is necessary for the Tn4652 transposition-dependent accumulation of phenol utilizing mutants in Pseudomonas putida. To enlighten the role of ColRS system in P. putida we searched for target genes of response regulator ColR using a promoter library. Promoter screening was performed on phenol plates, to mimic the conditions under which the effect of ColR on transposition was detected. Library screen revealed a porin-encoding oprQ and the alginate biosynthesis gene algD occurring under negative control of ColR. Binding of ColR to the promoter regions of oprQ and algD in vitro confirmed its direct involvement in regulation of these genes. Additionally, a porin-encoding ompA_PP0773 and a type I pili gene csuB were also identified in the promoter screen. However, it turned out that ompA_PP0773 and csuB were actually affected by phenol, and that the influence of ColR on these promoters was indirect. Namely, our results show that ColR is involved in phenol tolerance of P. putida. Phenol minimal inhibitory concentration (MIC) measurement demonstrated that colR-minus strain did not tolerate elevated phenol concentrations. Our data suggest that increased phenol susceptibility is also the reason for inhibition of transposition of Tn4652 in phenol-starving colR-minus bacteria. Thus, current study revealed the role of ColRS two-component system in regulation of membrane functionality, particularly in phenol tolerance of P. putida.

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