Aging flies are simply crawling with bacteriaboth inside and outbut their microbial infestations dont seem to hasten the insects toward death, according to a new study in the August issue of the journal Cell Metabolism, a publication of Cell Press. The findings suggest that the energy the flies expend to fight their burgeoning bugs comes without a longevity trade-off, the researchers said.

Its a surprise, said John Tower of the University of Southern California. Even though the flies were accumulating so much bacteria and a robust immune response to that bacteria, its not limiting how long the flies live. The question is, if its not bacteria that limit life span, then what is it" Weve reduced the number of possibilities.

Towers interest in the problem stemmed in part from the fact that humans and some bacteria are known to have mutually beneficial relationships. People gain nutrients and energy with the aid of bacteria, and the microbes are provided with a buffered environment, carbohydrates, and other nutrients, the researchers noted. Since immune function is impaired with age, it might be expected that bacterial load would increase or be otherwise altered as people grow older. Indeed, studies have found shifts in humans intestinal bacteria with age and evidence that bacteria may blossom in the prostate and other organs of the elderly.

To explore the consequences of such changes in bacteria with age in greater detail, the researchers looked to flies. Drosophila flies are emerging as an ideal model system in which to study most aspects of immunity, including innate immune pathwayswhich represent the bodys first line of defensecellular immunity, and the metabolic effects of infection, Towers group said.

The researchers showed that the insects exhibited dramatic increases in many types of bacteria during aging, both inside the body and on the surface. It was gradual across their life span, Tower said. It went from virtually u
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Contact: Erin Doonan
edoonan@cell.com
617-397-2802
Cell Press
7-Aug-2007