Bugs Join Forces against Pesticide: Gut Bacteria Allow Insects to Survive Exposure to Chemical

Article excerpt

Insects and microbes have teamed up against a pesticide commonly sprayed on crops. In lab tests, swallowing a bellyful of certain bacteria protected bugs from the toxic chemical.

This detoxifying diet is the first example of a symbiotic relationship that provides insecticide resistance, scientists report online April 23 in the Proceedings of the National Academy of Sciences.

"Mechanisms of insecticide resistance have been thought to be encoded by the insect genomes themselves," says Yoshitomo Kikuchi, a microbiologist at the National Institute of Advanced Industrial Science and Technology in Hokkaido, Japan. "Our findings overturn the common sense."

Kikuchi and his colleagues treated pots of soil with fenitrothion, a cheap insecticide used worldwide. Burkholderia bacteria, which can disarm the pesticide and break it down for its carbon, flourished in the dirt.

The insecticide-munching microbes also thrived inside young bean bugs, Riptortus pedestris, exposed to seedlings grown in the pots or fed the bacteria by the researchers. A single insect can support an estimated 100 million Burkholderia cells in its gut. In return for providing a comfortable living space, infected bean bugs acquired a new tolerance to the pesticide in the lab. Most of the insects survived doses of fenitrothion that killed 80 percent or more of their undefended comrades within five days. …