First, the OM preparations of bacteria grown at 0.4 or 0.8% of glucose revealed an additional OM protein (~50 kD) that was barely detectable in the membrane preparations of bacteria grown at 0.2% of glucose. A similar pattern was CHIR-99021 purchase observed also for the OMP preparation of www.selleckchem.com/products/oicr-9429.html central cells (data not shown). Mass spectrometric analysis identified this hunger-repressed protein as OprE encoded by PP0234 (Figure 6A). Second, the amount of OprB1 inversely correlated with initial glucose concentration

in agar plates being highest at 0.2% and lowest at 0.8% of glucose (Figure 6A). Note that the differences observed for OprB1 amounts in OM correlated well with the lysis data of the colR mutant on different glucose plates (Figure 5). All these results support the hypothesis that selleck screening library an elevated expression of OprB1 due to nutrient limitation generates membrane stress that is not tolerated by the colR mutant and results in the lysis of most vulnerable subpopulation of bacteria. Figure 6 Profiles of the outer membrane proteins of the P. putida PaW85 (wt) and the colR -deficient (colR) strains under different growth conditions. OM proteins were purified from the solid medium-grown P. putida PaW85 (wt) and colR-deficient (colR) strains cultivated on the agar plate sectors

as illustrated in Figure 5A. A. OM protein profiles of 24-hour-old peripheral subpopulations of bacteria grown on solid medium with 0.2, 0.4 or 0.8% glucose. Location of OprB1, OprE, and OprF is indicated by the arrows. B. OM Fossariinae protein profiles of peripheral and central subpopulations grown for 24 hours on 0.2% glucose solid medium. The quantified protein bands are indicated by the arrows. C. The ratio of OprB1 to OprF in different subpopulations of the P. putida wild-type and the colR mutant strains grown for 24 hours on 0.2% glucose solid medium. The OprB1/OprF ratio was calculated from the data obtained from at least two independent protein preparations and from three independent gel runs. Mean values and 95% confidence intervals are presented. When analysing the composition of OM proteins of bacteria

grown on 0.2% glucose (conditions that promote lysis), we repeatedly observed a slight difference between the wild-type and the colR mutant regarding the relative proportions of OprB1 and OprF. The colR mutant showed a tendency to have less OprB1 and more OprF in OM than the wild-type. This was most clearly seen when the OM protein profiles of peripheral subpopulations of two strains were compared (for representative results see Figure 6B). In order to quantify the proportions of OprB1 and OprF in the OMP preparations, we analysed the SDS-PAGE images with ImageQuant TL program. Quantification showed that OM of the wild-type indeed contained relatively more OprB1 than that of the colR-deficient strain (Figure 6C, p = 8,6e-07 and p = 6,8e-04 for preparations from peripheral and central cells, respectively).