June 13, 2008
Dear Professor Lenski,
Skepticism has been expressed on Conservapedia about your claims, and the significance of your claims, that E. Coli bacteria had an evolutionary beneficial mutation in your study. Specifically, we wonder about the data supporting your claim that one of your colonies of E. Coli developed the ability to absorb citrate, something not found in wild E. Coli, at around 31,500 generations. In addition, there is skepticism that 3 new and useful proteins appeared in the colony around generation 20,000. A recent article about your claims appears in New Scientist here: http://www.newscientist.com/channel/life/dn14094-bacteria-make-major-evolutionary-shift-in-the-lab.html
Submission guidelines for the Proceedings of the National Academy of Science state that "(viii) Materials and Data Availability. To allow others to replicate and build on work published in PNAS, authors must make materials, data, and associated protocols available to readers. Authors must disclose upon submission of the manuscript any restrictions on the availability of materials or information." Also, your work was apparently funded by taxpayers, providing further reason for making the data publicly available.
Please post the data supporting your remarkable claims so that we can review it, and note where in the data you find justification for your conclusions.
I will post your reply, or lack of reply, on www.conservapedia.com . Thank you.
Andy Schlafly, B.S.E., J.D. Conservapedia
Dear Mr. Schlafly:
I suggest you might want to read our paper itself, which is available for download at most university libraries and is also posted as publication #180 on my website. Here's a brief summary that addresses your three points.
1) "... your claims, that E. Coli bacteria had an evolutionary beneficial mutation in your study." We (my group and scientific collaborators) have already published several papers that document beneficial mutations in our long-term experiment. These papers provide exact details on the identity of the mutations, as well as genetic constructions where we have produced genotypes that differ by single mutations, then compete them, demonstrating that the mutations confer an advantage under the environmental conditions of the experiment. See papers # 122, 140, 155, 166, and 178 referenced on my website. In the latest paper, you will see that we make no claim to having identified the genetic basis of the mutations observed in this study. However, we have found a number of mutant clones that have heritable differences in behavior (growth on citrate), and which confer a clear advantage in the environment where they evolved, which contains citrate. Our future work will seek to identify the responsible mutations.
2. "Specifically, we wonder about the data supporting your claim that one of your colonies of E. Coli developed the ability to absorb citrate, something not found in wild E. Coli, at around 31,500 generations." You will find all the relevant methods and data supporting this claim in our paper. We also establish in our paper, through various phenotypic and genetic markers, that the Cit+ mutant was indeed a descendant of the original strain used in our experiments.
3. "In addition, there is skepticism that 3 new and useful proteins appeared in the colony around generation 20,000." We make no such claim anywhere in our paper, nor do I think it is correct. Proteins do not "appear out of the blue", in any case. We do show that what we call a "potentiated" genotype had evolved by generation 20,000 that had a greater propensity to produce Cit+ mutants. We also show that the dynamics of appearance of Cit+ mutants in the potentiated genotypes are highly suggestive of the requirement for two additional mutations to yield the resulting Cit+ trait. Moreover, we found that Cit+ mutants, when they first appeared, were often rather weak at using citrate. At least the main Cit+ line that we studied underwent an additional mutation (or mutations) that refined that ability and led to a large improvement in growth on citrate. All these issues and the supporting methods and data are covered in our paper.
- Richard Lenski
Dear Prof. Lenski,
This is my second request for your data underlying your recent paper, "Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli," published in PNAS (June 10, 2008) and reported in New Scientist ("Bacteria make major evolutionary shift in lab," June 9, 2008).
Your work was taxpayer-funded, and PNAS represents that its authors will make underlying data available. I'd like to review the data myself and ensure availability for others, including experts and my students. Others have expressed interest in access to the data in addition to myself, and your website seems well-suited for public release of these data.
If the data are voluminous, then I particularly request access to the data that was made available to the peer reviewers of your paper, and to the data relating to the period during which the bacterial colony supposedly developed Cit+. As before, I'm requesting the organized data themselves, not the graphs and summaries set forth in the paper and referenced in your first reply to me. Note that several times your paper expressly states, "data not shown."
Given that this is my second request for the data, a clear answer is requested as to whether you will make the key underlying data available for independent review. Your response, or lack thereof, will be posted due to the public interest in this issue. Thank you.
Andy Schlafly, B.S.E., J.D.
cc: PNAS, New Scientist publications