Therefore, we investigated the effects of Fed-Batch cultivation supernatant constituents, after extraction by dichloromethane, on growth and PM expression in R. rubrum. After removing the dichloromethane by evaporation, the dry residue was resuspended in acetonitrile (ACN). These extracts were then added to R. rubrum cultivations in flask experiments (Figure 3). The Selonsertib cost addition of extracts from R. rubrum cultures caused a strong reduction in PM production. TEW-7197 research buy To rule out that the effect was caused by the addition of ACN, pure ACN was added to control cultures. ACN alone slightly lowered PM synthesis if added in volumes larger than 20 μl. However, the ACN-containing

culture extract produced significantly stronger effects. Addition of excess ACN (500 μL) diminished the effect of the extract. Figure 3 Effect of different amounts of AHL extract on PM production (A) and initial growth Selleckchem PHA-848125 rate (B) of R. rubrum . Cell-free supernatants from the stationary phase of a microaerobic Fed-Batch

cultivation, in which PM production is completely inhibited, were extracted with dichloromethane, evaporated to dryness and resuspended in acetonitrile (ACN). Different volumes of AHL extract (black bar) or ACN (gray bars) were added to the culture at the point of PM induction (A) or prior to inoculation (B). Initial growth rates of cells were calculated from data obtained from the first 20 hours of the experiment. Growth conditions are comparable to those used for Figure 2.

The shown data represent the average Rapamycin of two biological replicates (two shake-flask cultivations of each extract amount were cultivated at the same time. The extract used in this experiment was obtained from the harvest of one Fed-batch cultivation). Error bars were calculated by error propagation of the deviations of three equivalent experiments (for each experiment extracts from one Fed-Batch cultivation were supplemented to shake-flask cultures). In contrast to PM production, the initial growth rate (μ 0) increased in proportion to an increasing volume of pure ACN (Figure 3B, grey bars). However, the ACN-containing R. rubrum extract stimulated the highest growth rate when added at 20 μL and the initial growth rate declined with an increasing extract volume. The addition of 500 μL extract appeared to retard the growth rate, although this effect was not observed with the same volume of ACN (Figure 3B). We note that Figure 3B also shows a steadily increase in the initial growth rate of the control cultures when only increasing amounts of the solvent ACN were added. The growth stimulation strongly suggests that R. rubrum is capable of utilizing ACN as a source of carbon and/or nitrogen. A gene encoding a bifunctional nitrilase (YP_425830) is annotated in the genome sequence of the strain employed in our study.