News about the human microbiome

How Microbes Defend and Define Us

This article from the New York Times, by Carl Zimmer, should be obligatory reading for anybody who wants to characterize bacteriae as either good or bad.

Some quotes:

"Dr. Khoruts mixed a small sample of her husband’s stool with saline solution and delivered it into her colon. Writing in the Journal of Clinical Gastroenterology last month, Dr. Khoruts and his colleagues reported that her diarrhea vanished in a day. Her Clostridium difficile infection disappeared as well and has not returned since. "

"In the mouth alone, Dr. Relman estimates, there are between 500 and 1,000 species. “It hasn’t reached a plateau yet: the more people you look at, the more species you get,” he said. The mouth in turn is divided up into smaller ecosystems, like the tongue, the gums, the teeth. Each tooth—and even each side of each tooth—has a different combination of species. "

"Scientists are even discovering ecosystems in our bodies where they weren’t supposed to exist. Lungs have traditionally been considered to be sterile because microbiologists have never been able to rear microbes from them. A team of scientists at Imperial College London recently went hunting for DNA instead. Analyzing lung samples from healthy volunteers, they discovered 128 species of bacteria. Every square centimeter of our lungs is home to 2,000 microbes. "

" 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. "

"One of those tasks is breaking down complex plant molecules. “We have a pathetic number of enzymes encoded in the human genome, whereas microbes have a large arsenal, ...”

"The Imperial College team that discovered microbes in the lungs, for example, also discovered that people with asthma have a different collection of microbes than healthy people. Obese people also have a different set of species in their guts than people of normal weight."

My reflection: It's going to take a LONG time before reductive science manages to make sense of the interactions between all these bacteriae and ourselves. In the mean time, we'd better approach the subject with some humility. Remember how the polio epidemic got started? It turned out that the main cause was cleanliness: People were meeting a new microbe later in life than they used to.

:-J