E. coli as a model system for evolutionary adaptation to environmental change?

E coli at 10000x, original

Tomorrow’s edition of Nature has a paper that may be interesting for some from a biological / genetic viewpoint. The story they spin around that, however, should serve as advice to all of us how to sell a fairly theoretical study to a top-ranked journal. The authors state their motivation as follows:

As anthropogenic activities are leading to environmental change at unprecedented rapidity, it is critical to understand how the rate of environmental change affects both demographic and genetic underpinnings of evolutionary rescue.

So far so good – so, how would we improve our understanding how the rate of environmental change (I can only assume they refer to climate change etc.) affects the potential of evolutionary adaptation?

We allowed hundreds of populations of Escherichia coli to evolve under variable rates of increase in concentration of the antibiotic rifampicin. We then genetically engineered all combinations of mutations from isolates evolved under lower rates of environmental change. By assessing fitness of these engineered strains across a range of drug concentrations, we show that certain genotypes are evolutionarily inaccessible under rapid environmental change.

Am I naive to translate those findings into: Evolution needs some time? To be fair, the rest of the paper concentrates on the exact genetic mechanisms that lead to the adaptation to rifampicin, which is actually fairly interesting, but I feel one has to bend over backwards to see how a better understanding of how E. Coli adapts to an antiobiotic is informative about the mechanisms that allow (or don’t) evolutionary adaptation of ecosystems under environmental change, and what the “lower” in the title means quantitatively for real ecosystems.

3 thoughts on “E. coli as a model system for evolutionary adaptation to environmental change?

  1. Yes, the relevance to real-world policy responses to real-climate change obviously can be questioned. But to be fair, that “hook” is just the usual sort of throwaway line everybody puts in all their papers these days. If that hook really bothers you, I assume you must be really bothered by half the papers in ecology these days! (and I’m not saying you shouldn’t be, I’m just saying you shouldn’t single this paper out on those grounds) FWIW, I highly doubt that that throwaway “hook” had much if anything to do with getting this paper into Nature. Contrary to what some people (not you) sometimes seem to think, you cannot just say “Climate change FTW!” and get a paper in Nature. 😉

    More substantively, I don’t think it’s fair to summarize the take home message of this paper as “evolution takes time”. The genetic mechanisms that you set to one side, and that you grant are interesting, are actually the whole point of the paper. It’s precisely because of those genetic mechanism (epistatic interactions among mutations, such that mutations that are adaptive in one genetic background are maladaptive in others) that adaptation to rapid environmental change is difficult. It’s not simply that rapid environmental change doesn’t allow enough time for a given level of adaptation to occur.


    • Hi Jeremy,

      what I meant by “evolution needs time” is that the message I got from the paper for global change ecology is that evolution will need time to adjust to intermediate climatic conditions when climate change takes place, but you’re right to point out that the main scientific achievement of the paper is to demonstrate that intermediate antibiotic conditions do indeed “level” the path for the adaption to high concentrations by favoring specific epistatic mutations that are not easily attainable if the organism is immediately exposed to a high antibiotic concentration.

      About the relevance: I don’t mind dressing research in the fashion of the time, but I found they were doing it to an extent that borders deliberately confusing the reader – their hook fishes for people interested in global or climate change, but what can those really learn from this paper? The main problem for climate change is that we have no idea at all how fast species can adopt, and which adaptations are easy to attain for which species / group. They sure could have hooked with antibiotic resistance instead, which seems a much more realistic application to me, they even discuss this later in the paper, but apparently that was not considered sexy enough to make it in the abstract.

      I should maybe have said more clearly that I quite liked the paper, it’s very clearly written, and the experiment is nice, I just found the motivation with climate change somewhat absurd (but maybe that’s simply my lack of mental flexibility).


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