A “diauxic shift” to a new beginning

Throughout grad school I’ve had many ideas I wanted to write about, or tools I’d developed that I wanted to explain and share, but these never seemed quite “serious” enough to spend time on. So, for the most part, I abandoned my previous hobby of blogging in favor of spending more time in lab.

But some of these ideas seemed fun or maybe could have led to interesting research directions. At the very least, they might have helped others with technical tasks. So it always felt remiss to not air them out somehow.

Now that I’ve finished my PhD, and at least for now will not be writing many more papers, I want to make a more serious effort to communicate my mini-ideas. I’ve also entered a new field of biology, and am trying to make sense a lot of new and fascinating literature that I’d like to share with a broader audience (or, well, I’d be happy with “beyond my own head”).

In the spirit of change, I will call this new blogging project “Diauxic Shift”, after the phenomenon, discovered by Monod and Jacob, where microbes pause growth between consuming different nutrients so they can induce the appropriate metabolic genes. This is a great example of what I love not only about biology, but about the history of science. A simple but mysterious observation, properly quantified and carefully thought about, leads to a much broader and more fundamental insight into life — cells can make decisions, and do so by means of an almost unimaginable orchestration of specialized molecules.1 It was the appreciation of this fact that originally made me want to become a biologist.

I also like the somewhat silly analogy of me switching fields and jobs to microbes switching metabolic modes. I do often feel as if I’ve eaten up my preferred nutrients and am figuring out how to grow again.

There is an even farther-fetched analogy, which I will entertain because makes the blog title triply appropriate. Ultimately I hope to write here about an issue that I have started to feel is part of my mission as a biologist: develop technologies to allow humans to more sustainably live on this planet.

What might the diauxic shift have to do with this? I found during my PhD that microbes can actually avoid the diauxic shift by pre-activating the genes they need to survive on alternative resources. This gives them a fitness advantage in certain conditions because they never need to stop growing when the first resource runs out. What’s cool is that this is not a universal behavior — some strains of yeast are “anticipators” while others are “procrastinators”, with a whole spectrum in between. The reason for this, I speculate, is that early preparation has a growth cost for cells, so there are cases where either strategy can be evolutionarily advantageous.

Of course, it seems much more clear for humans and our resources that preparation is the correct strategy right now, but even so there are those that argue the opposite. Head-scratching analogies aside, it’s clear that our society needs to make some big decisions now, and I hope that my work and writings, here and elsewhere, will make a positive contribution to these decisions.


1I think about this a lot ever since reading Horace Freeland Judson’s “The Eighth Day of Creation”, a wonderful account of the discoveries of the DNA double helix and the genetic code that also weaves in an account of Monod and Jacob’s discovery of the Lac operon and messenger RNA. Another amazing book, Sean Carroll’s “Brave Genius”, about the friendship between Jacques Monod and Albert Camus set around WWII, cements my eternal fanboyhood of Monod.

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