Bacteria and Sexual Desire

Drosophila melanogaster, mating couple. Male i...
Sex, fruit flies and their bacteria. We are affected too. Image via Wikipedia

Most of us know that we have lots of organisms in our guts to help us digest food (and if we forget it, Jaime Lee Curtis is willing to tell us in her Activia commercials!) The microorganisms are so important that termites cannot digest wood without their gut bacteria and we cannot break down all our food without the human kind.  What you might not know is that we have hundreds of trillions of organisms especially along our GI tract, respiratory system and skin.  And they do a lot more than digest.  They fight infections, create certain vitamins, form a living wallpaper on the intestinal wall to protect our bloodstreams from debris.  Some help make us fat or thin.  But did you know that our bacteria might affect our sex drive?  At least they do for white fruit flies, known as Drosophilia.  If you kill off their gut bacteria, they won’t mate the same way.

In the February 2011 issue of Surgery News, Lazar Greenfield wrote:

It has long been known that Drosophila raised on starch media are more likely to mate with other starch-raised flies, whereas those fed maltose have similar preferences. In a study published online in the November issue of the Proceedings of the National Academy of Sciences, investigators explored the mechanism for this preference by treating flies with antibiotics to sterilize the gut and saw the preferences disappear (Proc. Nad. Acad. Sci. U.S.A. 2010 Nov. 1).

In cultures of untreated flies, the bacterium  L. plantarum was more common in those on starch, and sure enough, when L. plantarum was returned to the sterile groups, the mating preference returned. The best explanation for this is revealed in the significant differences in their sex pheromones. These experiments also support the hologenome theory of evolution wherein the unit of natural selection is the “holobiont,” or combination of organism and its microorganisms, that determines mating preferences.


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