The Economist

Appearances can be deceptive. Householders have been seduced for years by the idea of fitting out their kitchen with easy-to-wipe surfaces, and throwing out those old wooden cutting boards in favour of shiny new plastic ones. So much more hygienic, it is thought.

Dean Cliver and Nese Ak, two researchers at the University of Wisconsin-Madison, beg to differ. They set out to find ways of decontaminating wooden kitchen surfaces and ended up finding that such surfaces are pretty good at decontaminating themselves.

Working with wood from nine different species of tree, and with four sorts of plastic and even an old rubber chopping board, the results were always the same.

When they spread their gut-wrenching bacteria - salmonella, listeria and E. coli - over the various samples and left them there for three minutes, the level of bacteria on the plastic or rubber remained unchanged while the levels on the woods plummeted, often by as much as 99.9 per cent. Left overnight at room temperature, the bacteria on the plastic actually multiplied, while the wooden surfaces cleaned themselves so thoroughly that Dr. Cliver and Ms. Ak could not recover anything from them.

At first sight, these results seem astonishing. But, unlike polymer chemists, plants have spent hundreds of millions of years fighting off bacteria. They should be quite good at it by now. And trees might be expected to be the best of the lot. After all they live longer - not only longer than most plants, but longer than the animals as well. And even when a tree is dead, its wood can hand around for decades, resisting the attacks of micro-organisms. Slaughtering a few should be child's play.

Dr. Cliver and Ms.Ak do not yet know exactly what is happening, but their guess is that the porous structure of the wood is soaking up the fluid with the bacteria in it. Once inside, the bacteria stick to the wood's fibres and are "strangled" by one of the many noxious anti-microbial chemicals with which living trees protect themselves - exactly which, they have not yet worked out. But they are searching. In the meantime, perhaps surgeons should search out their old chopping blocks.

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