Down on the farm: evolution bites back

Most of the time we don't even think about the invisible world of microbes. It's only when we get an infection, such as food poisoning from contaminated meat, that we grudgingly admit the power that bacteria have over us.

So perhaps we should pay attention to findings published in this week's Science, that show that two food bugs that cause illness in humans are jumping the species barrier and merging.

Campylobacter jejuni and Campylobacter coli are the bacteria  in question, food bugs that between them are thought to account for 400,000-odd cases of food poisoning a year in the UK and five times that in the US. Martin Maiden of Oxford's Department of Zoology tells us that his team has uncovered evidence that these bacteria are 'despeciating' - in a sense putting evolution into reverse - converging as a result of very recent exchanges of genetic material.

All part of Nature's rich tapestry? Not exactly. Martin comments: 'It’s highly plausible that this change is the unintended consequence of the introduction of intensive agricultural practices.’ He goes on to explain that the effect of human activity, such as farming, on the environment is creating new ecological niches for bacteria. These niches may be in intensive farms or the acidic areas around mines. So humans, unintentionally, are creating new opportunities for and selection pressures on bacteria that then adapt or merge to take advantage.

No one is saying that the C. jejuni-C.coli convergence is an immediate threat to human health (it's just a good reminder to prepare and cook your meat properly) but it does suggest that we need to learn much more about the effect human activity has on bacterial evolution - especially when it comes to illness-causing bugs in our foodchain.

Related news story: Free range ‘no increased infection risk’ for chickens

Image: Campylobacter jejuni via Wikimedia Commons 

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