Parasite Supports Host By Becoming Fertility Aid (4/28/2007)

Bacteria that commonly infect insects have evolved from parasites to being a fertility aid. The bacteria could eventually be targeted as an option for pest control in order to kill common human disease carriers such as mosquitoes.

Researchers at the University of Melbourne have followed the evolution of Wolbachia bacteria and found that they have rapidly changed from being parasitic and therefore detrimental to their insect host, to engaging in a mutualistic relationship where both bacteria and insect benefit because the insects gain enhanced fertility.

Professor Ary Hoffmann and Dr Andrew Weeks from the Department of Genetics at the University of Melbourne have used the Californian fruit fly (Drosophila) as a model in their experiments.

The Wolbachia bacteria are spread from an infected male to an uninfected female. The researchers found that within 20 years, infected females have gone from having reduced fertility with a 15-20% reduction in egg production, to a 10% increase in egg production under laboratory conditions. Their results suggest that smaller, but similar changes are occurring in nature.

"This is the fastest rate of evolution for this relationship so far; we know of no previous examples where an evolutionary shift towards mutualism has been observed in a period of decades in nature" said Dr Andrew Weeks.

"Because this increased fertility seems to provide an advantage in nature, we predict that the bacteria will continue to be present in the insects for future generations and may even evolve to become essential to the host" said Professor Ary Hoffmann.

"We could take advantage of this evolving situation by killing off the bacteria inside insects such as mosquitoes. Because the bacteria increase fitness, this strategy could reduce mosquito numbers and their ability to spread diseases like malaria and dengue fever".

The research is published in the April issue of PLos Biology.

Note: This story has been adapted from a news release issued by the University of Melbourne

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