Scientists Discover Bacterium in Mosquitoes' Gut That Destroys Malaria

By Veronique Greenwood | May 13, 2011 1:55 pm

As the number of bacteria in mosquitoes’ guts (x axis) went up,
the malaria parasite levels dropped faster than a cartoon anvil.

What’s the News: We know the bacteria living in our guts are important to our health—but the bacteria in mosquitoes’ guts could be too. Researchers have discovered a species of mosquito gut bacteria that destroys the malaria parasite, keeping the disease from spreading to humans. This explains why some Anopheles mosquitoes (the only genus that transmits malaria) don’t spread it, and it spurs the imagination towards possible ways of tamping down the disease.

How the Heck:

  • Scientists have long wondered why some Anopheles mosquitoes don’t seem to carry malaria, while others of the same species or strain do. Mosquitoes’ immune response to the malaria parasite, Plasmodium, and their gut bacteria were known to play a part in this, but to uncover exactly what was going on, scientists collected gut bacteria from wild mosquitoes and watched what they did to the parasite in Petri dishes.
  • They identified one bacterium in particular that severely impaired the parasite’s development. When they fed it to mosquitoes, parasite levels plummeted (see graph above).
  • To find out how the bacteria were doing it, they tried adding and removing all kinds of chemicals to mixtures of the bacteria and the parasite to see what effect they had on the bacteria’s parasite-fighting ability.
  • What they found was that the bacteria were bombarding the parasites with oxygen free radicals, lone oxygen atoms that damage DNA. The clincher? When they added vitamin C, a powerful antioxidant and fighter of free radicals, to the mixture, suddenly the parasites could grow.

What’s the Context: Malaria infects about 300-500 million people a year, and serious bucks are being spent on attempts to destroy it for good. Most approaches are still pretty far away from being implemented. What’s promising about this discovery is that it doesn’t involve complicated genetic engineering—mosquitoes just have to ingest the bacteria to get the effects.

The Future Holds: Our attempts to engineer our own gut flora are still in their infancy (fecal transplants, anyone?), but as ingesting the bacteria is all that’s required to get the mosquitoes protected, this approach could have real promise as an anti-malaria measure. More research, of course, is required.

One thing is clear: Keep the mosquitoes away from the orange juice.

Reference: C. M. Cirimotich, Y. Dong, A. M. Clayton, S. L. Sandiford, J. A. Souza-Neto, M. Mulenga, G. Dimopoulos. Natural Microbe-Mediated Refractoriness to Plasmodium Infection in Anopheles gambiae. Science, 2011; 332 (6031): 855 DOI: 10.1126/science.1201618

Image credit: Science


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