Deepa Agashe

---

Adaptation is driven by beneficial mutations, whose supply
determines the pace and dynamics of evolution. Increasing
the mutation rate increases the supply of beneficial
mutations, giving mutators an evolutionary advantage.
However, genetic changes that increase mutation rate
typically also change mutation bias, which can in turn
influence access to beneficial mutations. Specifically, we
recently showed that reversing the ancestral mutation bias
in Escherichia coli from transitions (Ts) to transversions
(Tv) unlocks access to under-sampled types of mutations,
expanding the supply of beneficial mutations. To
disentangle the effects of mutation rate and bias, we
experimentally evolved E coli mutators in different
environments. Both mutation rate and bias facilitated early
adaptation, with bias shifts additionally influencing the
underlying mutational mechanisms and parallelism. Thus,
the evolutionary advantage of mutator strains also derives
from mutation bias, which can significantly shape the
dynamics and outcome of adaptation.

---

NCBS Bangalore
0.02
Contact: Joachim Krug