A Blog by Ed Yong

Bug becomes instantly resistant to insecticide by swallowing the right bacteria

Many insects eventually evolve to resist insecticides. This process typically takes many generations and involves tweaks to the insect’s genes. But there is a quicker route. Japanese scientists have found that a bean bug can become instantly resistant to a common insecticide by swallowing the right bacteria.

The bug forms an alliance with Burkholderia bacteria, and can harbour up to 100 million of these microbes in a special organ in its gut (see arrow above). Some strains of Burkholderia can break down the insecticide fenitrothion, detoxifying it into forms that are harmless to insects. In fields where the chemical is sprayed, these pesticide-breaking bacteria rise in number. And if bugs swallow them, they become immune to the otherwise deadly chemical.

I’ve written about this story for The Scientist, so head over there to read the details of the study.

To me, the alliance is fascinating because the bug is coping with a new environmental challenge by bolstering its own genome with that of a microbe.

Many creatures rely on microscopic partners to safeguard their health. Insects inherit beneficial bacteria from their mothers, which help them to resist other bacteria that would cause disease, or fight off parasitic wasps that would usurp their bodies. Our own gut bacteria could be important for preventing nasty infections. And even bacteria can resist antibiotics by incorporating the genes of infectious viruses into their own DNA. Nature is full of bigger things using smaller things as living preventive medicine.

If the bean bug example stands out, it’s because many of the other cases involve microbes that are passed down from parent to offspring. The bug, however, has to get its bacteria from the surrounding soil with every new generation.

Two of the scientists I spoke to said that this makes perfect sense. Nancy Moran pointed out that bacteria have a much wider range of metabolic abilities than animals do. If you’re facing a man-made poison, chances are there’s some microbe that can break it down. And Molly Hunter pointed out that this metabolic diversity tends to plummet in bacteria that become dependent on their hosts. These internal symbionts tend to lose important genes, so free-living microbes may be a better source of detoxification genes. Hunter delightfully described it as an “open-source symbiosis”.

Reference: Kikuchi, Hayatsu, Hosokawa, Nagayama, Tago & Fukatsu. 2012. Symbiont-mediated insecticide resistance. PNAS http://dx.doi.org/10.1073/pnas.1200231109

4 thoughts on “Bug becomes instantly resistant to insecticide by swallowing the right bacteria

  1. I wonder whether also other insects can do the same. If some agricultural pest would do that, finding out would be crucial to optimize pest control (and why not, reduce use of agrochemicals). To those who can’t help but have a utilitarian vision of science, this is yet another reminder of the importance of basic research. “What, you want to spend money and effort to study what’s in the gut of a bug?! Are you mental man, especially with the economic crisis there’s better things to do!”. Like spending millions in producing pesticide which may be potentially useless (other than detrimental to the environment)? Yeah right

  2. This is the very reason that trying to engineer plants with an enclosed poison is pointless. The bugs will figure out a defense almost as fast as we can develop another “superplant.” Meanwhile, more and more poisons are sprayed on the plants that we intend to eat. Stop the madness!!!

  3. Can this be used to ameliorate bee colony collapse disorder? At least, in as much as it is caused by pesticides?

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