With bacteria against insect plagues
Scientists have discovered another bacterium that has similar insecticidal properties to the widespread Bacillus thuringensis. The bacterium Photorhabdus luminescens contains a toxin that has been shown to be effective against a variety of insects. It promises to be a powerful, safe, and environmentally friendly weapon in the fight against insect plagues. In the world of biological pest control, Bacillus thuringensis has so far been the "king of insecticides". A bacterium with broad anti-insect uses, it acts as a mainstay of pest control for foresters, farmers, gardeners and homeowners looking for a safe, natural method. It is the only bacterium that has found widespread commercial use. As a result, it has held a monopoly on insect control worth hundreds of millions of dollars.
In concentrated doses, its toxin can be used as a spray or fed directly to insects. However, the greatest possible application lies in the transfer of the toxin-producing genes of the bacteria to cereal plants. Scientists have already transferred the genes responsible for the insecticidal properties of Bacillus thuringensis to important cereal crops. Over the next year, approximately 12,000 to 20,000 km of transgenic corn will be available in the US Midwest alone2grown.
According to Richard french-Constant, professor of toxicology at the University of Wisconsin-Madison, “this use of transgenic crops […] is perhaps the greatest artificial experiment in natural selection in insect populations since the introduction of synthetic insecticides a while ago half century.“
The incentive to add your own insecticides to crops is great. American farmers now spend more than $575 million a year on chemical pesticides just to protect one crop, corn.
The next step, already prepared, is to transfer these genes to accessible crops. According to the researchers, however, it will still be three to five years before a product is actually put on the field.
Now a team of scientists from two labs at the University of Wisconsin-Madison working with DowElanco scientists in Indianapolis are hoping to use a newly discovered bacterium with similar insecticidal properties. The bacterium, Photorhabdus luminescens, contains a toxin that has been shown to be effective against a wide range of insects, from cockroaches to boll weevils. It promises to be a powerful, safe, and environmentally friendly weapon in the fight against insect plagues.
"It's a voracious pathogen. A bacterial cell can kill an insect," says Jerald Ensign, a professor of bacteriology at the University of Wisconsin-Madison. Photorhabdus is a widespread bacterium that lives as a symbiont inside soil-dwelling roundworms called nematodes (or roundworms) that invade insects. Once the nematodes are inside a host insect, the bacteria are released, killing the insect and allowing the bacteria and nematodes to reproduce. The insect is used as food for the nematodes. The Photorhabdus bacteria even leave a clear trail: corpses left by the bacteria glow in the dark because the microorganisms produce luminescent proteins in addition to a powerful insecticide.
These new findings from the Wisconsin group were presented December 17 at the Entomological Society of America Annual Meeting. Studies have now revealed a large number of Photorhabdus strains that are effective against insects. The discovery of a new family of insecticidal bacteria is all the more important given that some insects have already developed resistance to the Bacillus thuringensis toxin in recent years. Each of the Photorhabdus strains produces a distinct form of the toxin.
"It is important to have substitutes for the Bacillus thuringensis toxin before the restricted range leads to many crop failures in North America," says french-Constant. "If they don't exist, that's an open invitation to natural selection to induce resistance in insects, and we'll lose control."
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