Written by: Richard Lenski
Primary Source: Telliamed Revisited
I had a terrific visit to Scotland last week. The graduate students in the Institute of Evolutionary Biology at the University of Edinburgh invited me to speak there. Thanks especially to Manon Ragonnet and Sam Lewis for organizing and hosting my visit.
It seems a bit extravagant to fly overseas for a one-hour lecture. But there was much more to my visit than just the lecture. I spent a day and a half in meetings with students and faculty, where we discussed their projects and plans, and I was impressed by the quality of science all around. Before my visit, I hadn’t realized how many groups in Edinburgh were working on microbial evolution, including the evolution of infectious diseases and experimental evolution.
I spent my last day in Scotland with over a dozen graduate students hiking around and up North Berwick Law, a once-volcanic peak near the Firth of Forth. The weather was beautiful during my first two days in Edinburgh, but for this day out, we were treated to “authentic” Scottish weather. Through the fog and rain, though, we could make out the shoreline and a couple of the nearer islands. Better yet, the company was great, full of small talk and big ideas.
I spoke on “Time Travel in Experimental Evolution” – a 50-minute overview of the long-term evolution experiment, or LTEE, in which we’ve observed and analyzed more than 50,000 generations in the lives of 12 populations of E. coli, all founded from the same ancestral strain and all evolving in, and adapting, to the same, simple lab environment.
That works out to some 1,000 generations per minute, so I had to speak really fast.
Seriously, though, it’s a challenge to decide what to include, and hence what to exclude, from an experiment that’s been running for more than 25 years. Besides presenting some results, I need to explain the original motivation for the experiment; describe its structure, rhythm, and a few key methods; and leave time to summarize the findings and acknowledge the people who’ve done the work.
I also need to have both a narrative and a theme that flow through the talk. In my talk, the narrative revolves around time travel: how we use the rapid generations of bacteria, the ability to freeze and revive cells to compare organisms that lived at different times, and the opportunity to replay evolution by restarting from past generations. The theme is the tension between chance and necessity – between idiosyncratic and repeatable events – and what these 12 populations can tell us about the processes that govern evolution.
I always include some of the latest results that are on my mind, but which haven’t yet been published or, in some cases, even fully analyzed. Out of necessity, though, many exciting but older results don’t get mentioned in the ever-evolving versions of my talk.
There’s a longer story to be written about the LTEE, one that pulls together all the findings, old and new. I keep holding off, though, because there’s always another big result or two just around the corner. After we’ve nailed those down, then I can pull everything together. But along comes another major new finding, and another …
I like to say that the LTEE is the experiment that just keeps on giving. Between the element of time, the inventiveness of the bacteria (even in their tiny confined worlds), and the many talented and dedicated students, postdocs, and collaborators who’ve worked on the LTEE, there appears to be no end in sight.
Indeed, when I got home, I had an email from a journal editor, asking my coauthors and me to revise a paper. Back to work!