We have talked about the Meyer, 2012 paper from Lenski’s group where the phage adapted to use OmpF as a receptor. Quite a few trials were run, and the sequence of mutations in the virus protein J were tracked. Interestingly, zero synonymous mutations were found. As the paper explains:
First, all 248 independent mutations in the 51 sequenced J alleles were nonsynonymous, whereas the expected ratio of nonsynonymous to synonymous changes is 3.19:1 under the null model for the ancestral J sequence. This great excess is evident even if we include only the 82 nonsynonymous mutations in the 24 isolates that did not evolve the new receptor function.
I wonder if anyone can explain why there there were zero synonymous mutations?
The paper presents this fact as evidence for strong selection, which I think is clearly a strained argument. So what’s going on?