Love Me, Love My Bugs

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Love Me, Love My Bugs


ScienceDaily (Dec. 3, 2010) — Could the bacteria that we carry in our bodies decide who we marry? According to a new study from Tel Aviv University, the answer lies in the gut of a small fruit fly.

Prof. Eugene Rosenberg, Prof. Daniel Segel and doctoral student Gil Sharon of Tel Aviv University's Department of Molecular Microbiology and Biotechnology recently demonstrated that the symbiotic bacteria inside a fruit fly greatly influence its choice of mates.

The research was done in cooperation with Prof. John Ringo of the University of Maine, and was recently published in the Proceedings of the National Academy of Sciences (PNAS).

Love, marriage and fruit flies

Based on a theory developed by Prof. Rosenberg and Dr. Ilana Zilber-Rosenberg, the scientists propose that the basic unit of natural selection is not the individual living organism, plant or animal, but rather a larger biological milieu called a holobiont. This milieu can include plant or animal life as well as their symbiotic partners. In the case of animals, these partners tend to be microorganisms like intestinal bacteria.

"Up to now, it was assumed that the host organism undergoes evolution on its own, while its symbiotic bacteria undergo their own evolution," Prof. Rosenberg says. "The mechanism that we discovered enables evolution to occur more rapidly in response to environmental changes. Since a generation is shorter for bacteria than for multicellular organisms, they genetically adjust more quickly to changes in the holobiont," says Prof. Rosenberg.

Conducting their experiments on the rapidly-reproducing fruit fly, the scientists were able to test this new theory. The first experiment repeated a study carried out two decades ago by a Yale University researcher, in which a fly population was divided in half and fed different diets -- malt sugar versus starch. A year later, when the flies were re-integrated as one group, those who had been fed starch preferred starch-fed mates, while the sugar-fed flies preferred mates of a similar nutritional background. The repeat experiment carried out by the Tel Aviv University researchers shows that this dietary influence takes effect within just a generation or two rather than over an entire year.

In their second experiment, the Tel Aviv University team repeated the first, but with the addition of an antibiotic, which killed the bacteria and eliminated the specific mate preference. The mating process became random, with no dietary influence.

In subsequent experiments, the researchers successfully isolated the bacterial species responsible for reproductive isolation in flies with diet-related mating preferences, and found the bacteria Lactobacillus plantarum to be present in greater numbers in starch-fed fruit flies than in sugar-fed flies. When L. plantarum was reintroduced into the antibiotic-treated flies, the preferential mating behavior resumed -- proving that this bacterial species is at least partly responsible for the mating preference.

Rewriting Darwin?

Finally, in cooperation with Prof. Avraham Hefetz of Tel Aviv University's Department of Zoology, the team analyzed the sexual pheromones produced by the fruit flies. There turned out to be differences in pheromone levels between the two groups of flies -- differences that again disappeared after administering antibiotics.

"The finding indicates that pheromone alterations are a mechanism by which we can identify mating preferences. We therefore hypothesize that it is the bacteria that are driving this change," Prof. Rosenberg says. He adds that these discoveries have implications for our entire understanding of natural selection -- something which may even lead to the development of a new theory of evolution.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.



"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck

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Fascinating and entirely

Fascinating and entirely plausible.  I remember some of the people I have met with vastly different diets from mine - they smelled funny.  And I have a varied diet, liking and partaking of cuisine from a number of different cultures.

But I don't think it would rewrite Darwin or evolutionary theory.  After all, Darwin did not understand genetics and his theory does not address it specifically.  All he said was something would cause a mate preference - some factor that would make that species member more attractive.  I don't see why it couldn't be - at least in part - diet and/or bacteria/parasite loading.  It doesn't change the fact that the more attractive members of the species are the ones to get their genes into the next generation.


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I married

I guess I could tell my ex-wife "Did you know we married each other for our germs ?,".  LOL.

Interesting article, but can you see the implications ?

New advertisement : find the partner that has the right bacteria for you !

“It is proof of a base and low mind for one to wish to think with the masses or majority, merely because the majority is the majority. Truth does not change because it is, or is not, believed by a majority of the people.”
― Giordano Bruno