Jeffrey Gordon

I heard a talk by Dr. Jeffrey Gordon, not Jeff Gordon, for those of you wondering. I was pretty excited about the talk because Dr. Gordon has been putting out some very interesting work concerning the human microbiome and the role of microbial communities in our gut in determining how the host responds to its environmental conditions and diseases.

The talk was very well attended, a testament to the interest in this new field. Dr. Gordon, as seems to be the custom nowadays, introduced the concept that we are more bacterial than eukaryotic, at least by sheer number of cells. I think he mentioned we are 90% microbial and 10% “us” and referred to the collective organism as a supra-organism.

The largest diversity of microorganisms living in our body are located in our gastrointestinal tract. Dr. Gordon alluded to the fact that the modern world with the ability to travel from one place to another, the exposure to many different kinds of foods and the 60 years in which humans have been regularly using antibiotics can really affect the diversity of bacteria in our gut.

2 out of the 100 phyla of bacteria known dominate. These are the firmicutes and the bacteroidetes. There are 8 others in smaller proportion. There is at least one Archaeon. There might be more phages than bacteria in our gut!

There are many unknowns like what is the geography lengthwise and depthwise. What things affect diversity? How robust are the communities to new bacteria introduced and how much functional redundancy is there in the supra-organism?

Are these bacteria passed down from parents to kids? It seems from his work with mice that yes. Siblings share a much more common bacterial signature.

Testing feces in humans shows bacterial diversity is controlled by at least two effects which are the legacy effect (bacteria are passed down by families, so you can track these movements) and the host-gut environment (shown by moving zebrafish microbes into germfree mice and moving mouse bacteria into germfree zebrafish. In the first case the mouse had a mouselike microbiome even though very different proportions were originally introduced. The zebrafish also had very zebrafish-like microbiomes even though they had mouse bacteria put into them!).

Another interesting vignette I remember from the talk dealt with the Archaeon, a methane consuming bacteria, that lives in the gut. It somehow interacts with B. theta and a microbial food web is set up. B. theta alters its foraging habits in the presence of the Archaeon. I think B. theta consumes a completely different set of polysaccharides from mucus creating a different environment in the host. The application? Instead of trying to alter the delicate balance of firmicutes and bacteroidetes, Gordon suggested that in the absence of the Archaeon the body would not have the same metabolites to pick up and could make a big difference in weight loss! I think the details are a bit fuzzy but I’m sure you can read more about it on his site!