Could bacteria learn to match a signal that didn't occur regularly to a probable future event? If so, the bacterium could improve its chances of survival by turning on a preemptive response.
Because E. coli gets warmer when it enters a human mouth and then must soon contend with low oxygen levels as it passes into the large intestine, the team reasoned that the bacterium might use temperature as a cue to prepare for the upcoming lack of oxygen. Indeed, when the researchers turned up the heat in a dish of E. coli, the bugs dialed down activity in genes that normally operate in high-oxygen conditions. But the true test came when the team flipped the normal association, growing the bacteria in conditions in which high oxygen levels followed temperature increases. Less than 100 generations later, the bacteria stopped turning on their low-oxygen response after exposure to high temperatures, suggesting that they had evolved to break the association.
The study is the "first convincing demonstration" that bacteria can use environmental cues to anticipate events, says Michael Travisano, an evolutionary biologist at the University of Minnesota, Twin Cities. The work could open up new ways to explain puzzling behavior of microbial pathogens, which might use predictive signals to change their cell surfaces and avoid a host's impending immune attack.