Posted on Thu, Apr. 14, 2005

Scientists discover hundreds of strains of bacteria in intestines

BY GLENNDA CHUI
Knight Ridder Newspapers

SAN JOSE, Calif. - (KRT) - One hundred trillion bacteria live in your
gut - 10 microbes for every human cell in your body.

In the first comprehensive survey of this realm, Palo Alto, Calif.,
scientists found 395 strains of bacteria living in the intestines of
healthy people. Most were previously unknown to science.

They discovered that each person's collection of bugs was unique and
varied from place to place within the gut, which is more than 30 feet
long when uncoiled.

Some bacteria cling to the intestinal wall, while others hitch rides on
bits of undigested food, forming colonies that researchers jokingly
call "Whovilles."

Sounds gross, but it's actually a good thing, because we probably
couldn't live without our microbes, said Dr. Paul Eckburg, a
postdoctoral fellow at the Stanford University School of Medicine who
led the research.

They're so vital for our well-being that some researchers consider them
an organ of the human body - one that helps us digest food, inactivate
poisons and fight disease. The microbes, known as the intestinal flora,
may also help guide the normal development of our guts.

Other scientists suggest that the genes of all those bacteria
constitute a second human genome, and that we will never fully
understand the workings of our bodies until we understand them, too.

"You can regard ourselves, human beings, as a composite of species,"
said Dr. Jeffrey I. Gordon, director of the Center for Genome Sciences
at Washington University in St. Louis, who was not involved in the
study.

"We are a superorganism," he said, "composed of human cells and
microbial cells."

Taken together, the bacteria in our guts contain 100 times more genes
than our human cells do. The ecosystems they form are the densest known
in nature. Our feces are about half bacteria by weight.

Yet we know more about the microbes of the soil and the seas than we
know about these intimate companions, said Lora Hooper, an immunologist
at the University of Texas Southwest Medical Center.

Gordon said the report, published Thursday in the online edition of the
journal Science, is the first comprehensive inventory of a microbial
community so vast that it is "mind-boggling."

When the gut microbes are in balance, they help keep us well. Thrown
out of balance, they may contribute to disease.

Eckburg and his team, including Dr. David Relman of Stanford and the
Veterans Affairs Palo Alto Health Care System, have been looking at
both extremes.

In the new study they examined snippets of intestine and feces from
three healthy people from Canada. They used genetic probes to fish out
more than 13,000 gene sequences and determined that those genes
belonged to 395 species of bacteria. More than 60 percent had never
been seen before.

Once a complete inventory of these microbial genes is in hand, Relman
said, the team hopes to find patterns of gene activity that indicate
good health, illness or even the possibility that someone might get
sick soon.

The group is also looking at microbes from people with inflammatory
bowel conditions, such as ulcerative colitis and Crohn's disease.

Other members of the team are trying to determine where babies get
their intestinal bugs: From their mothers during delivery? From food,
or breast milk, or the things they're constantly putting in their
mouths?

A separate study at Washington University, reported last year, raises
the intriguing possibility that intestinal bugs may help determine if a
person is prone to getting fat.

Scientists compared germ-free mice with normal mice fed the same chow.
The normal mice had 40 percent more body fat - an indication that their
gut microbes helped them wring more nutrition from their food.

It may be that some people have more efficient gut microbes than
others, Gordon said. The more efficient they are, the more energy they
would harvest from food and store as fat, making their owner more prone
to obesity.

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INTESTINAL FLORA

Your intestinal flora, by the numbers:

One hundred trillion: Number of bacteria that live in your gut

10: Number of microbes for every human cell in your body

30: Length of the gut, in feet, when uncoiled

50: Percentage of human feces that consist of bacteria, by weight

Source: San Jose Mercury News reporting

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© 2005, San Jose Mercury News (San Jose, Calif.).