TY - JOUR T1 - Evolutionary Stalling in the Optimization of the Translation Machinery JF - bioRxiv DO - 10.1101/850644 SP - 850644 AU - Sandeep Venkataram AU - Ross Monasky AU - Shohreh H Sikaroodi AU - Sergey Kryazhimskiy AU - Betül Kaçar Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/11/24/850644.abstract N2 - Biological organisms are modular. Theory predicts that natural selection would steadily improve modules towards their performance optima up to the margin of effective neutrality. This classical theory may break down for populations evolving in the clonal interference regime because natural selection may focus on some modules while adaptation of others stalls. Such evolutionary stalling has not been observed and it is unclear whether it limits the power of natural selection to optimize module performance. To empirically characterize evolutionary stalling, we evolved populations of Escherichia coli with genetically perturbed translation machineries (TMs). We show that populations with different suboptimal TMs embark on statistically distinct trajectories of TM optimization. Yet, before TMs approach the margin of effective neutrality, the focus of natural selection shifts to other cellular modules, and TM optimization stalls. Our results suggest that module optimization within an organism may take much longer than suggested by classical theory. ER -