The Human Ecosystem

We've written before about the microbiome and fecal transplants. Carl Zimmer has a great piece in the New York Times about the human body as an ecosystem for microbes and the various ways we interact with them: "How Microbes Defend and Define Us". A snippet:

Some microbes can only survive in one part of the body, while others are more cosmopolitan. And the species found in one person’s body may be missing from another’s. Out of the 500 to 1,000 species of microbes identified in people’s mouths, for example, only about 100 to 200 live in any one person’s mouth at any given moment. Only 13 percent of the species on two people’s hands are the same. Only 17 percent of the species living on one person’s left hand also live on the right one.

Read the whole thing.

[h/t: Why Evolution is True]

Off with their Heads!

I've written before about a possible beneficial side effect to circumcision - the reduction in HIV infection risk.

In an effort to identify other changes in circumcised penises (other than the obvious), and to drum up business for the local mohel, scientists have examined differences in the penis microbiome in a recent paper published in PLoS ONE. They conclude:

The anoxic microenvironment of the subpreputial space may support pro-inflammatory anaerobes that can activate Langerhans cells to present HIV to CD4 cells in draining lymph nodes. Thus, the reduction in putative anaerobic bacteria after circumcision may play a role in protection from HIV and other sexually transmitted diseases.

While the main thrust of the paper is the reason for the previously mentioned HIV risk reduction, there are some other interesting outcomes for the reduced numbers of an anoxic environment and the corresponding bacteria. Mike the Mad Biologist has more:

This seems to be a much more compelling finding: circumcision might reduce bacterial vaginosis. While bacterial vaginosis isn't dangerous except in very limited circumstances, it still is a nuisance. To me, that's the compelling finding, although vaginas probably make news editors giggle, so that's probably why vaginosis wasn't covered.

Somehow I still don't think people will be queueing up...

Coprophagia & the human microbiome

I found this interesting article on the evolution of symbiotic bacteria in the human gut in PLoS. A good summary article accompanies it. Some interesting implications of the work are that considerations for the evolution of 'our' bacterial genomes should be considered when looking at human evolution. In fact a hot topic in the blogosphere is the possibility of a human microbiome project. (check out this link for sure.) Without these bacterial communities we would not be able to acquire much of the energy from cellulose that we get when we eat plant material. I would assume then, and it is mentioned in the summary, that perhaps the makeup of the bacteria in the human gut would be influenced by the hosts diet. Would a vegatarian then have more bacteria able to break down cellulose for example thus making the host a more efficient user of plant energy? Since we humans lack the complex digestive system of the ruminant, as we are evolved to be omnivorous, perhaps vegetarians should consider eating their own feces to more efficiently extract energy from plant matter.
Coprophagia, or eating your own poop, is a term first brought to my attention by fellow bayblabite, Alfred Russel Wallace. My pet bunny practices this behavior, however, I have, thankfully, rarely noticed it doing this. One of the best sites I have seen on the subject of bunny poop eating is a must see and informative. For example, the site points out, if you overfeed your bunny you might inhibit coprophagia and malnurish your pet. The disgustingly cute animated gifs add to the atmosphere of this site.