So, What Else is New?

At the year's end, the media have been paying special attention to microbes.  Newspapers, radio, and TV have found microbial stories worthy of their attention.  Here is a sample:

Obesity and the gut flora. Practically everyone who listens to or reads any sort of media must know by now that someday we may be able to lose weight by modifying our gut flora.  A couple of papers from the lab of Jeffrey Gordon (A and B) point to what goes on in the bowels of both people and mice. Two bacterial groups dominate in the colon, the Gram negative Bacteroidetes (mainly Bacteroides), and the Gram positive Firmicutes (mainly Clostridium). Their ratio, however, varies with the host's heft. The F/B ratio is higher in the obese, both mice and human.  It looks like the F's are better at breaking down foodstuff and providing more energy to the host.  Studies of this sort open a lot of questions but they keep Google busy.  Enter gut flora and you get thousands of relevant sites.  We must thank Gordon and colleagues for shifting the public's attention from killer spinach to the intricacies of the interactions between microbes and humans in health, not only in disease. 

Comments

[Robert S. Fulghum]

Do bacteria in the lower gut really make fat people fat or do fat people's metabolism control the relative number of different species in the GI tract ?

W.E.C. Moore showed in the rumen of cattle (not lower GI flora) that the animal controls the fermentation rate - at least of cellulose. He had twin steers from each he removed the entire contents of the rumens, washed out the rumens, and replaced the contents of each steer's rumen in it's twins rumen.

Having previously measured the rate of the digestion of cellulose in each animal and finding a difference, he repeated the digestion experiment in the animals after the rumen contents had been replaced. He found the digestion rate was characteristic of the individual animal rather than characteristic of the rumen contents (biota) replaced in the other animal. In other words, the animal, not the biota controlled the fermentation rate of cellulose.
I don't remember if he ever published this and I have long since given away my reprint files.
And maybe - just maybe - these were unique animals. One of them learned to lick the light switch and he would turn the lights on in the barn at night !

My best regards to you, Elio.
Bob

[moselio schaechter]

Stanley is right insofar as the studies on humans go. However, in their mouse paper, the authors colonized germ-free mice with intestinal microbes from either fat or the lean mice. Their claim is that the "fat bugs" made the mice obese, the "skiny bugs" did not. Surely this is nto the last word on thsi matter

[Stanley Maloy]

But the cause vs effect question remains -- is the change in composition of gut microbes DUE TO differences in diet and metabolism that correspond to excess weight or does the change in composition of gut microbes PROMOTE the process leading to excess weight?