Historical Contingency Causes Divergence in Adaptive Expression of the lac Operon.

ABSTRACT: Populations of Escherichia coli selected in constant and fluctuating environments containing lactose often adapt by substituting mutations in the lacI repressor that cause constitutive expression of the lac operon. These mutations occur at a high rate and provide a significant benefit. Despite this, eight of 24 populations evolved for 8,000 generations in environments containing lactose contained no detectable repressor mutations. We report here on the basis of this observation. We find that, given relevant mutation rates, repressor mutations are expected to have fixed in all evolved populations if they had maintained the same fitness effect they confer when introduced to the ancestor. In fact, reconstruction experiments demonstrate that repressor mutations have become neutral or deleterio

SUBMITTER: Karkare K 

PROVIDER: S-EPMC8233506 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature