Fig. 4.

High expression levels of groE are tolerated in populations evolving with strong genetic drift effects. (A) Expression of groE was measured at three points of the evolution of bottlenecked populations: Generation 0, generation 1.8K, and generation 4K. We compared the expression of three lineages, the control lineage pΔgroE (gray horizontal bar), the lineage with groE under the control of l-arabinose inducible promoter (pgroE) evolved in the presence of l-arabinose (blue bar), and the same lineage pgroE evolved in the absence of l-arabinose (orange bar). (B) We quantified the expression level as the mean number of pixels (±SE) by Western blotting using hybridization with monoclonal GroEL antibody (ABCam #ab905022 at 1:1,000) at different time points expressed as generations. Bars correspond to lines evolved at 37 °C. Bottlenecked lines were rescued at these time points from glycerol stocks and grown simultaneously under arabinose induction conditions (+) or in media without the inducer arabinose (−).