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Nematode Germ Warfare: Truth can be stranger than fiction

© Neal Rolfe Chamberlain

One of the most memorable scenes in the movie Alien was of the baby alien bursting out of the chest of the human character Kane. We all say that can't possibly happen on good old planet earth. However, such scenes do occur almost everyday. The exceptions being that the alien creatures are really nematodes and the poor victim is an unsuspecting insect larva.

Certain nematodes (entomophagous nematodes) after being ingested by insect larvae will work their way into the blood of the insect and then kill its host using a previously unknown toxin. The nematodes then reproduce and the young live off the dead insect host until they are ready to make their own ways in the world.

Recently, researchers at the University of Wisconsin reported in Science (June 26, 1998; Volume 280, Pages 2050 and 2129-2131) purification of the toxin that causes the insect's untimely death. Come to find out the toxin is not actually made by the nematode but by a bacterium called Photorhabdus luminescens. The bacteria live in the gut of the nematode. The nematode releases Photorhabdus luminescens and the bacteria then produces the toxin in the host insect. The toxin by some unknown mechanism then kills the insect but not the nematode. Talk about germ warfare! These nematodes have worked it out to a science.

The great thing about this particular toxin is that it will kill a wide variety of insects. Because of this it may turn out to be a very useful means of controlling insects. Other researchers have been able to place a different insect toxin, called Bt toxin, from another bacterium called Bacillus thuringeinsis, in plants. The plants make Bt toxin and when insects eat the plant they die. Unfortunately, insects may be able to become resistant to Bt. Therefore, another toxin like the one from Photorhabdus luminescens may be useful to also genetically engineer in plants.

As one researcher mentions a number of these nematodes have similar life cycles and use their resident bacteria's toxins to help them gather food. Maybe we have another source of less damaging insecticides for the future.

For more information on this nematode and Photorhabdus luminescens:

1. Genetic Engineering News
2. News from the University of Wisconsin

Did you know that nematodes can be used to control beetles that eat your roses. Go to Mark Whitlaw's article at Suite101.com.

Take Care and Think Microbiologically!

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