Jo Handelsman discusses a paper that found gut microbiota can influence sexual fitness in an invasive pest.

The Mediterranean fruit fly is one of the most damaging agricultural pests in the world. A common strategy to reduce its population consists of releasing sterilized industrially grown flies out into the wild in the hopes that they will steal females from virile males. It turns out, however, that the sterilized males are not as lucky in getting the attention of the ladies. A recent paper—selected by F1000 Faculty Member Jo Handelsman, a microbiologist at Yale—has a surprising explanation for the altered males’ inability to attract females: their gut microbiota ( ISME J , 4:28-37, 2010).

TS: Why would intestinal microbes affect the sexual performance of an organism?

JH: We know that the gut microbiota of many organisms controls the most surprising breadths of activities and physiology. In humans we’re finding that gut...

TS: Is this the first link between gut microbes and sexual behavior?

JH: As far as I know, yes.

TS: Authors Edouard Jurkevitch and colleagues at the Hebrew University of Jerusalem had previously found that the guts of wild fruit flies are home to a predominant community of Klebsiella bacteria, which carry out nitrogen fixation and help with metabolism, among other things. In this study, they found that the sterilized flies experience a significant reduction in the Klebsiella population and an increased level of potentially harmful Pseudomonas. This suggests that the health of an organism depends on a delicate balance of commensal bacteria being maintained.

JH: In a healthy organism there is a complex community that’s balanced and functioning in a way that’s beneficial to the host. If it gets disrupted—and that disruption can be due to host factors or environmental factors—then we start to see aberrations in the physiology of the host. Those manifest in outright disease or just conditions that make the host a little less vital. In this case it looks like getting rid of the Klebsiella presents a biological void in the community for Pseudomonas to flourish.

TS: When the researchers fed the sterilized flies a live dose of Klebsiella, they were more likely to copulate with females in the wild. So it’s as simple as reconstituting the original microbe population in the gut?

JH: It seems that way. All they did was restore that one bacterial species and they seemed to restore the original sexual behavior and success. It’s entirely possible that it’s a nutritional effect and Klebsiella is perhaps a significant source of nitrogen for the host. But it’s also possible that Klebsiella is producing hormones that are affecting sexual behavior or performance. It’s been shown in other species that bacteria can produce key pheromones for mate attraction.

TS: In the future, would diets infused with live bacteria be used to treat diseases that are caused or exacerbated by an altered gut microbe composition?

JH: That’s one direction that personalized medicine is going. If we could introduce bacteria or use bacteria that would kill off other bacteria that are harmful, we might be able to restore health to a host. Another aspect of this is, because the gut microbiota affects the chemistry of the entire body, as this article shows, it’s going to be increasingly important to understand the gut microbiota in individual humans as we prescribe treatments for disease.

I don’t know if one day there are going to be microbial probiotics to change sexual attractiveness, but I think that’s something we have to wonder about after reading this article. We’re not really attracted to each other, we’re attracted to each other’s microbes.

Handelsman’s lab studies soil microbial diversity and microbes in the guts of insects. You can access her review of the paper at:

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