colon, however, it provides the most suitable atmosphere for
these bacteria—and the concentration of microbes there
shoots up to 10^11 bacteria per gram. It’s the Miami of the GI
tract.
Part of the reason these bacteria are so high in number in
the large intestine is that that’s where your “tenants” expect
to find an abundant source of sustenance. You see, the gut
microbiome is composed of a kind of bacteria called
commensals, which comes from the Latin word
commensalis, meaning “sharing a table.” They’ve earned
this name because every time we eat, they wait silently to be
fed, like thirty trillion obedient dogs. But what do they eat?
Thrown into a modern restaurant, commensal bacteria
would skip the menu entirely and head straight for the salad
bar. It’s there that these little critters would find the food that
they love to chow down on: plant fibers. These fibers
provide a form of carbohydrate that is inaccessible to us and
passes through the stomach and small intestine undigested.
When those fibers finally make it down to the large
intestine, the microbes get to experience the equivalent of a
Thanksgiving dinner!
MEAT AND THE MICROBIOME
A study published a couple of years ago sent shock waves
down the spine of many a health-conscious meat eater.
Researchers studying mice found that some species of gut
bacteria consume the amino acid carnitine, found in red