Two species of bacteria appear to reverse which is predator and which is prey depending on the temperature. Just a small temperature change is enough to cause the switch.
The soil bacteria Myxococcus xanthus is a social species that hunts in packs 鈥� it forms temporary, multicellular 鈥渟warms鈥� of individuals that chemically tear apart and soak up nutrients from other microbes. And its prey includes Pseudomonas fluorescens, a bacterium common in both soil and water.
at the French National Centre for Scientific Research and her colleagues originally set out to measure how well M. xanthus preyed on a variety of species 鈥� not just P. fluorescens 鈥� under different conditions. As part of the experiment, they reared populations of P. fluorescens at two different temperatures: 32掳C (90掳F) and 22掳C (72掳F). Then, 2 hours later, they introduced prey species to the predatory M. xanthus at 32掳C.
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As expected, when P. fluorescens was reared at 32掳C, M. xanthus destroyed most of the population within four days. But surprisingly, the P. fluorescens reared at 22掳C 鈥渟laughtered M. xanthus to extinction鈥�, Vasse and her colleagues wrote in the paper. They realised that cooler-reared P. fluorescens secreted a chemical compound that could degrade and destroy other bacteria.
In addition, the team observed that P. fluorescens grew rapidly after wiping out M. xanthus. This means that it was probably consuming nutrients from, and thus preying on, its one-time predator.
鈥淸This research] challenges the idea of having 鈥榝ixed鈥� roles within communities,鈥� says Vasse. 鈥淭hey can change so fast, so easily and so radically. It鈥檚 very brutal.鈥�
at the Scripps Institution of Oceanography in California says bacteria have been seen changing their observable traits in response to environmental conditions before. 鈥淏acteria are all pretty good at adaptation and niche shifting to suit their needs,鈥� he says.
But the study suggests that scientists should be 鈥渧ery careful鈥� when claiming microbes play fixed roles in their sometimes combative, sometimes cooperative communities, he says.
PLoS Biology
