The ColRS Two-Component System Regulates Membrane Functions and Protects Pseudomonas putida against Phenol

Abstract

As reported, the 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 determine the role of the ColRS system in P. putida, we searched for target genes of response regulator ColR by use of a promoter library. Promoter screening was performed on phenol plates to mimic the conditions under which the effect of ColR on transposition was detected. The library screen revealed the porin-encoding gene 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, the porin-encoding gene ompA PP0773 and the type I pilus 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 MIC measurement demonstrated that a colR mutant 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 mutant bacteria. Thus, the current study revealed the role of the ColRS two-component system in regulation of membrane functionality, particularly in phenol tolerance of P. putida.

The ColR/ColS Two-Component System Plays Multiple Roles in the Pathogenicity of the Citrus Canker Pathogen Xanthomonas citri subsp. citri

“…6). Similar effects of the ColR/ColS system on resistance to phenol and heavy metals have been reported in P. putida (19,24,32) and X. campestris pv. campestris (47).…”

“…campestris (47). Thus, ColR/ColS is involved in maintaining the structural integrity and function of the outer membrane (23,24) and contributes to X. citri subsp. citri growth in planta.…”

“…The ColR/ColS system was first identified in P. fluorescens and found to contribute to its colonization of plant roots (9). ColR/ ColS was further reported to be involved in different biological responses, including the transposition of a transposon (18), phenol tolerance (24), and heavy metal resistance (19) of Pseudomonas putida. Furthermore, ColR/ColS was shown to be involved in virulence, to regulate hrpC and hrpE operon expression, to contribute to the tolerance of X. campestris pv.…”

A Moderate Toxin, GraT, Modulates Growth Rate and Stress Tolerance of Pseudomonas putida

“…In addition to glucose-specific lysis phenotype, the colR-deficient P. putida also displays decreased phenol tolerance (33,34). As phenol mostly affects the cell membrane and GraT increases membrane permeability (Fig.…”

“…Besides being important for cell survival on glucose medium, the ColRS system also contributes to the phenol and heavy metal tolerance of P. putida (33)(34)(35), the root colonization ability of Pseudomonas fluorescens (36,37), and virulence of the human pathogen Pseudomonas aeruginosa and the plant pathogen Xanthomonas (38)(39)(40). Several lines of evidence suggest that all these phenotypes may be caused by impaired membrane homeostasis (31,33,37,40) of colRS-deficient bacteria. Recent selection of suppressors of lysis of the colR-deficient P. putida revealed among others an interruption of a predicted antitoxin gene PP1585 (31).…”