Your Own Personal Microbes

The new issue of THE ECONOMIST includes an article that just blew me away.  It's about the latest research on all the microbes that live in your gut.  

Your body harbors 100 trillion bacteria, ten times the number of cells you grew from your DNA, containing 3 million genes.  And they are yours: Humans differ vastly, it turns out, in the composition of this microbiome.  Some people have more of one kinds of microbes, other people have more of other kinds.  This has vast implications for health, most of which are just beginning to be explored.  Some findings so far:

Overweight people have more Firmicutes and fewer Bacteroidetes than thin people.  The later suppress the making of a hormone that facilitates fat storage, which is part of why Sally can eat a pint of Haagen-Dasz and not gain an ounce and Molly puts on three pounds looking at a picture of one M&M.  

Twin studies carried out by the Washington University School of Medicine in St. Louis show that even on the exact same diet, one twin can develop malnutrition and the other not, depending on their individual gut bacteria.

Formic acid produced by gut bacteria can contribute to heart disease, because formic acid signals to the kidneys how much salt to absorb back into the body or to excrete with urine.  Too much salt can damage arteries.

Scientists are also investigating possible links between gut bacteria and diabetes type 2, MS, and even autism.

Most amazing to me is the case of C. difficile, a bug that causes severe diarrhea, killing about 14,000 Americans each year.  Many strains have evolved resistance to even last-ditch antibiotics like vancomycin and metronidazole.    Worse, when these are tried, they kill off most of the patient's gut microbiome.  But at the Baptist Medical Center in Oklahoma City, doctors have come up with a successful--if gross--way to combat resistant C. difficile.  They give patients enemas with feces from healthy adults.  The new bacteria take over the gut and kill off the infection.

I have written stories about the evolution of disease microbes (including "Evolution," in my mini-collection THE BODY HUMAN, from Phoenix Pick).  The bacteria have an advantage in the medical arms race: They can evolve a new generation every twenty minutes, swapping plasmids to beef up each other's resistance to our drugs.  But we have brains on our side.  Despite the recent terrible onslaught of hospital-bred infections at NIH, there is lots of room for hope.  This excellent article illustrates why.