Micro-learning
June 18, 2009
They may not be salivating to the sound of a bell, but apparently two classically simple organisms, Escherichia coli and Saccharomyces cerevisiae, do anticipate changes in their environments and respond accordingly, according to a new study published online yesterday in Nature. E. coli consistently experience to maltose shortly after lactose in their journey down the digestive tract. When the scientists exposed E. coli to lactose, the genetic pathway of maltose digestion was partially activated, indicating that the bacteria were, somehow, preparing for what was coming. Even more impressively, S. cerevisiae was able to anticipate the stages of fermentation, in which sugar and acidity levels change, alcohol content rises, and the temperature is amped up. When the yeast felt the heat, genes for dealing with the stressors of the next stage of the process were activated.
The researchers were further able to show that these responses were indeed adaptive as the organism’s fitness was enhanced by this anticipation. And just like Pavlov’s dogs, E. coli strains that were repeatedly exposed to lactose but not maltose for 500 generations stopped activating the maltose genes. Thus, the authors say, “the natural temporal order of stimuli is embedded in the wiring of the regulatory network.” Could that be the case? Is the evolution of gene networks over evolutionary time really analogous to the evolution of the neural networks in our brains over the course of our lives? And could this “environmental anticipation…be ubiquitous in biology” as the authors suggest?
