Mean number of viable cells with time in five LTSP populations maintained in 400 ml LB culture, in 2 liter flasks. Error bars represent the standard deviation across the five populations. Number of viable cells was estimated by counting colony-forming units (CFU), following regrowth on LB agar plates. 9–11 clones from each of the five populations were sequenced, from three times points (red dots). 9–11 clones from each of three of the populations were sequenced from an additional three time points (blue dots).