Friday, March 14, 2014

Gut Microbial Ecology

Just in case you didn't catch what I discussed in class Thursday or wanted to know more:

The review I read stressed the importance of the microbial community structure rather than "good" and "bad" microbes (bacteria and archaea).  The community is structured by "top down" pressures from the host for functional redundancy and "bottom up" selection from resource partitioning for functional specialization.  Thus, the community is a result of coevolution between the host and the microbes.  With regard to function, diversification is continuous; the product of one microbe becomes the substrate for another.

What I found most engaging, however, was the mechanism that we acquire our gut community.  Researchers showed that we all get our initial community structure from our mothers.  Particularly, we get them from our mother's vagina and feces upon birth.  Babies born by natural birth have different colonization patterns than babies born by cesarean section.

Further support that the community isn't transmitted genetically: twins have the same level of similarity in their community as siblings.

Community is especially important for interactions with the immune system and with pathogenic communities.  The immune system regulates relative abundances of microbes not individual species and t-cells as well recognize the community not individual species.  Pathogens will interact differently with a healthy community than just a few of the "good" species.  Gut microbe community can therefore be used as a biomarker for health and susceptibility.

Furthermore, the community can influence metabolism of polysaccharides and susceptibility to obesity.  The two dominant divisions of bacteria in the gut are Bacteroidetes and Firmicutes.  Having more Firmicutes andd less Bateroidetes has been linked to obesity.  Microbial diversity in the intestine thus represents another form of heredity that could potentially be reprogrammed (maybe at birth) for a healthier society.

Ultimately, our living style (being fanatics about hygiene) could forecast our disease susceptibility in the future.  This might have huge implications for our society's prescribing of antibiotics that Abby discussed.

This is an easy to read and fascinating paper so if you have the time over break, check it out!

Ley, R. E., Peterson, D. A., & Gordon, J. I. (2006). Ecological and evolutionary forces shaping microbial diversity in the human intestine. Cell124(4), 837-848.

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