High Mutation Rate Variation in Gut Commensal Bacteria PLOS Bio Update #3 A. Williams

This study measures the mutation load and mutation rate of E. coli in lab mice, a rare paper in observing the evolution of gut commensal bacteria in its natural environment. They find mutations in DNA polymerase III which cause hypermutations, roughly 1000x higher than wild type, that last for over 1000 generations. The rapid mutation rate does produce novel, beneficial mutations that were expected to reach fixation given the fast generation time of the bacteria. However, the researchers found that the beneficial mutations only underwent partial sweeps, not fixation. They conclude that instead of positive selection acting on beneficial mutations, a different type of selection that instead maintains a large range of mutation rate variation (from 4-600 mutations per generation) is acting on this bacteria most strongly. This explains the mechanism for why we see similar community genetic compositions of gut commensal bacteria as this study in human microbiome research as well. 

-Alexis Williams


Ramiro RS, Durão P, Bank C, Gordo I (2020) Low mutational load and high mutation rate variation in gut commensal bacteria. PLOS Biology 18(3): e3000617. https://doi.org/10.1371/journal.pbio.3000617