Just in time to vie for "most overhyped scientific headline of 2010." The paper, "Bimodal gene expression in noncooperative regulatory systems" (available at h

Just in time to vie for "most overhyped scientific headline of 2010." The paper, "Bimodal gene expression in noncooperative regulatory systems" (available at http://www.pnas.org/content/107/51/22096.full http://www.pnas.org/content/107/51/22096.full), addresses the question of how bacterial populations achieve bimodal phenotypic distributions (basically, 1 blue cell goes in, 5 blue cells and 5 pink cells come out in a stable ratio, wtf). This phenomenon has previously been explained by a) cooperativity or b) feedback loops. Cooperativity is a phenomenon in molecular biology where the binding of one protein to, say, DNA will increase the rate of binding of a partner in crime (which can, say, turn a gene on) -- this is a relatively simple regulatory scheme that allows proteins that respond in linear fashion to their environment to produce a non-linear output. Feedback loops are pretty self-explanatory (one thing worth mentioning is that if the feedback loop involves the transcription of a gene, then it is much slower-acting than cooperativity). Cooperativity can explain the bimodal distribution problem because cooperative systems can act as "regulatory switches" where very small fluctuations in environment can result in very different behavior (see http://bioweb.wku.edu/courses/biol566/Images/MCB3-29hemoglobin.JPG http://bioweb.wku.edu/courses/biol566/Images/MCB3-29hemoglob... for a simplistic example of hemoglobin response to oxygen). Thus, one blue cell goes in, 10 cells come out with very slight environmental differences that are on this response-boundary - voila, 5 blue cells, 5 pink cells. Anyway, this paper shows that a cell population can have a bimodal phenotypic distribution without cooperativity, simply by having single proteins that respond in non-linear fashion to their environment. That's...a new statistical law? I don't have the time to fully deconstruct this paper, but after a skim I'm left with the question, "so how does a single protein achieve non-linear response?" This paper seems to provide a mathematical model without giving a good explanation for how it would be achieved in nature. The only answer I can come up with is cooperativity within the protein itself - say, cooperative allosteric regulation. Which would make the theoretical contribution of this paper a lot less exciting.