Fig. 4

Above Coomassie-stained SDS-PAGE of outer membrane proteins of cells expressing MATE-BglA (a), MATE-CelK (b) and MATE-CelA (c). Samples of cells with (+) and without (−) recombinant protein expression are shown. The sizes of relevant marker proteins (M) are denoted. The asterisks (*) indicate the bands assigned to the MATE fusion proteins. Below Flow cytometer analysis of P. putida cells expressing MATE-BglA (a), MATE-CelK (b) and MATE-CelA (c). Black P. putida cells expressing the respective MATE fusion protein. Grey Control cells without protein expression. The cells were cultivated to an OD of 0.5, protein expression was induced by the addition of 0.2 % l-arabinose, and after 4 h of further cultivation the culture was centrifuged. For SDS-PAGE analysis, outer membrane proteins of the respective cells were isolated according to a modified protocol of Park et al. [57]. For flow cytometer analysis, the cells were resuspended in PBS to a final OD of 0.4. After washing three times with PBS, the cells were incubated with a 1:50 solution of mouse anti-6xHis antibody for 30 min at RT, washed three times and then incubated with a 1:100 DyLight-633-coupled anti-mouse antibody for one hour at RT. After washing three times, the fluorescence of 50,000 individual cells was analyzed