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Blocking termites' defense mechanisms

Targeting immune system may offer sustainable pest control method

In what may offer an alternative to chemical pesticides, MIT researchers and collaborators from Northeastern University have discovered a novel way to make pest insects more susceptible to bacterial and fungal infections by blocking part of the immune defenses.

The new technique could offer a more sustainable way to protect crops and buildings from damage by termites and other pest insects, estimated at more than $30 billion per year.

The researchers, including senior author MIT Professor Ram Sasisekharan, report their findings in the Proceedings of the National Academy of Sciences the week of June 8.

"Dr. Sasisekharan's basic studies on innate immunity in insects have enabled him to devise a strategy to defeat them," said Pamela Marino of the National Institutes of Health's National Institute of General Medical Sciences, which partially supported the work. "The findings may lead to the development of new pesticides that pose a far lesser threat to human health than the chemical pesticides commonly used now."

Sasisekharan and his colleagues focused on specific proteins that insects embed in their nests. They found that the proteins, known as gram-negative bacteria binding proteins (GNBPs), act as a first line of defense against pathogenic bacteria and fungus.

When the proteins encounter bacteria or fungi they chop them up and expose the parts to the insects, priming their immune response.

Once the researchers discovered this function, they decided to try inhibiting the proteins, with an eye toward new methods of pest control. They found that a sugar called GDL (glucono delta-lactone), a naturally occurring derivative of glucose, disables the proteins and makes the insects more vulnerable to infection.

The researchers gauged the effectiveness of GDL in laboratory tests using termites. A few days after being exposed to GDL, all of the insects died from opportunistic pathogenic infections. A control group of termites not exposed to GDL lived twice as long.

Since this defense mechanism is only employed by certain insect species such as termites, locusts and cockroaches, GDL is harmless to beneficial insects such as ants, as well as other animals and plants. The same cannot be said for chemical pesticides now commonly used.

"When you look at the chemical pesticides now used, they're harmful not only for insects but also for humans too," said Sasisekharan, who is the Edward Hood Taplin Professor and director of the Harvard-MIT Division of Health Sciences and Technology (HST).

GDL, commonly used as a food preservative, is biodegradable and inexpensive, making it an attractive alternative to chemical pesticides.

The compound could be incorporated into building materials or paint to protect buildings from termites, said Sasisekharan, or could be made into a spray for use in fields where pests need to be controlled. It could also be used in food processing and storage facilities.

This research also lays the groundwork for possible development of similar agents to target pest insects, said Sasisekharan.

Lead authors of the paper are Ido Bachelet, postdoctoral fellow in HST, and Mark Bulmer, a former Northeastern postdoctoral fellow now at Towson University. Other authors are Rahul Raman, research scientist in HST, and Rebeca Rosengaus of Northeastern University.

The research was funded by the National Science Foundation and the National Institutes of Health.

A version of this article appeared in MIT Tech Talk on June 10, 2009 (download PDF).

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