Having the Right Gut Bacteria Improves Mating Chances of Male Fruit Flies

Adjusting the mix of bacteria in the guts of sterilized male fruit flies enables them to compete successfully against native males and improves the "mass male sterilization” method of biological pest control.

The sterile insect technique (SIT) is a method of biological control whereby millions of factory reared sterile male insects are released into the field. The sterile males copulate with wild females, who will then be unable to lay fertile eggs, thus reducing the pest population. This technique is commonly used to combat the Mediterranean fruit fly (Ceratitis capitata or medfly). However, this method has not proven to be as successful as expected, since sterile medfly males are less competent than native males in attracting and mating with wild females.

A paper published in the January 2010 issue of the ISME (International Society for Microbial Ecology) Journal provided an explanation for this phenomenon and a means for correcting it. Investigators at the Hebrew University of Jerusalem (Israel) analyzed the mix of bacteria living in the guts of irradiated and sterilized male medflies and compared the results to the population found in the guts of native male flies.

They found that although the Enterobacteriaceae family remained the dominant bacterial group present in the gut, the levels of Klebsiella species decreased significantly in the days after sterilization. In addition, they detected substantial differences in some bacterial species between the irradiated Vienna 8 fly strain and the wild strain. Most notable among these were the increased levels of the potentially pathogenic Pseudomonas species in the irradiated strain.

The investigators fed irradiated flies on a high protein diet enriched with Klebsiella oxytoca bacteria. They found that this diet promoted colonization of these bacteria in the gut while resulting in decreased levels of the Pseudomonas species. Flies fed on diets containing bacteria performed significantly better than classical sterile males in copulatory tests.

Contributing author Dr. Boaz Yuval, professor of entomology at the Hebrew University of Jerusalem, said, "Successful application of this approach can be applied to a variety of plant and animal pests, as well as to organisms that transmit human disease, thus making an important, organic, and environmentally friendly approach to pest control.”

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Hebrew University of Jerusalem