Monthly Archives: August 2016

Dynamics of genome evolution in E. coli

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Hi All,

The Lenski lab has just published a new paper in Nature that looks at the dynamics of genome evolution in E. coli populations over the course of the LTEE.  Here is the abstract:

Tempo and mode of genome evolution in a 50,000-generation experiment

Adaptation by natural selection depends on the rates, effects and interactions of many mutations, making it difficult to determine what proportion of mutations in an evolving lineage are beneficial. Here we analysed 264 complete genomes from 12 Escherichia coli populations to characterize their dynamics over 50,000 generations. The populations that retained the ancestral mutation rate support a model in which most fixed mutations are beneficial, the fraction of beneficial mutations declines as fitness rises, and neutral mutations accumulate at a constant rate. We also compared these populations to mutation-accumulation lines evolved under a bottlenecking regime that minimizes selection. Nonsynonymous mutations, intergenic mutations, insertions and deletions are overrepresented in the long-term populations, further supporting the inference that most mutations that reached high frequency were favoured by selection. These results illuminate the shifting balance of forces that govern genome evolution in populations adapting to a new environment.

I’m assuming the whole thing is pay-walled, but a pre-print copy (which may or may not be identical to the final version) is freely available here.

I’ve only read the abstract thus far, but the paper seems likely to touch on a variety of topics that folks here like to discuss. Have at it!

The psychology of (not) admitting mistakes

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To err is human. Mistakes are as inevitable as death and taxes, so why do many people find it so hard to admit them? Why will they go to great lengths to avoid doing so? What predisposes them to what I’ll call “mistake denial”?

An obvious first guess is that it relates to social status. We humans are a social species, and our standing in the eyes of others depends largely on our perceived competence. Mistakes whittle away at that perceived competence, and so a person who successfully avoids admitting a mistake has avoided a real social cost. There is a flip side, however. While successful mistake denial benefits the denier, unsuccessful denial exacts an even heavier social cost than admitting the mistake in the first place. The denier is seen not only as having made the mistake, but also of dishonestly and childishly trying to cover it up. Under this social cost model, then, we would expect people to deny their mistakes only when there was a reasonable likelihood of “getting away with it” — of successfully deceiving the audience.

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