What do you expect evolution to look like in a microbial population? Check out our new study offering a view of that over 1000 generations in yeast in the lab.
co-led by @alex_nguyen_ba, @jireva, in @MichaelMDesai 's labhttps://www.nature.com/articles/s41586-019-1749-3 …
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We've known for the past couple of decades that many microbial populations adapt in an incredibly dynamic way, with large numbers of beneficial mutations continuously arising and competing.
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But it has been difficult to observe the majority of those mutations: theory had predicted that most would be lost before reaching fractions of the population detectable by available methods.
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@alex_nguyen_ba and@jireva developed a remarkable new approach to continuously re-introduce enormous numbers of DNA barcodes into an evolving yeast population, one right next to the other in the genome.1 reply 0 proslijeđenih tweetova 1 korisnik označava da mu se sviđaPrikaži ovu nit -
By sequencing this genetic locus over time, we can measure the fractions of the population in different barcoded lineages.
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I then developed an approach to use this lineage frequency data to reconstruct the clonal structure of the population and to detect individual beneficial mutations.
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We see that the population carries dozens of competing beneficial mutations, and that it forms a sort of 'traveling wave' if you look at its distribution of fitness. This agrees with theoretical predictions.
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But it also exists in a limit that we don't currently have a good quantitative description for. Instead of proceeding smoothly, the wave exhibits large fluctuations as mutations cause clones to continuously leapfrog over each other!
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Wonderful stuff! For those wondering about leapfrog, here's where Phil Gerrish & I introduced the idea: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.372.6402&rep=rep1&type=pdf … See Fig 7 for simple illustration, in which successively dominant genotypes may -- or not, in case of leapfrog -- represent sequential substitutions.
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