Editor's Summary

A bioengineer gets schooled by Escherichia coli.

The ability to learn from situations and to predict certain outcomes sets us apart from many living things. It prevents many of us from chasing balls into busy streets or placing bottles of ethanol near Bunsen burners. Still, it didn't stop thousands of US researchers submitting applications for the National Institutes of Health's Challenge Grants — funded by President Barack Obama's economic stimulus package — despite an expected success rate little better than one or two per cent.

To enjoy the benefits of learning and predictive behaviour, we usually assume that you need a nervous system or at least a neuron. So it was surprising to read that Saeed Tavazoie at Princeton University, New Jersey, and his colleagues have demonstrated that bacteria can learn and exhibit anticipatory behaviour (I. Tagkopoulos et al. Science 320, 1313–1317; 2008). They show computationally and experimentally that Escherichia coli can learn temporal correlations between environmental stimuli — for example, that an increase in temperature is followed by a decrease in oxygen levels — allowing the bacteria to predict and prepare for future environmental changes.

The researchers show that this associative learning is accomplished by rewiring of biochemical networks. Strikingly, they also show that, like many of us, E. coli quickly 'unlearn' (in fewer than 100 generations) what they had learned in a new situation.

Now we know that bacteria can be taught such tricks, it will be interesting to see if we can use novel combinations of environmental stimuli to train microbes to efficiently convert biomass into energy sources, such as hydrogen or butanol. By providing E. coli with such an educational stimulus package, we may be able to boost the global economy.

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