Bacteria and people: In it together

June 12, 2012 By Faye Flam

Next time your digestive system malfunctions in some embarrassing way, you can always blame man's best friend - not the dog, but the bacterial cells that live in your intestines. Not everyone has a dog but we all have enormous communities of bacteria that help us digest food. They don't always do a perfect job, but without them we'd have a tough time surviving.

In fact, our bodies have about 10 times as many bacterial cells as , said David Artis, a at the University of Pennsylvania. "Some people have even joked that if one considers the meaning of life," he said, "it could boil down to us being vessels to carry around bacteria."

Artis has been studying our relationship to our resident microbes, the vast majority of which live in our intestines. Recently, he's focused on how they know to be so friendly and refrain from spreading around the body and making us sick.

He's found these so-called commensal bacteria aren't friendly by nature. If that enormous load of intestinal got out into other parts of the body, "they could kill us," he said. Luckily, our immune systems have evolved the ability to police these bugs, keeping them from spreading beyond the intestines, he said. It's a constant process of negotiation between our cells and theirs. When that symbiotic harmony breaks down, can escape and make us sick.

All animals carry around , said Rob Knight, an at the University of Colorado, Boulder. Bacteria are good at living with other organisms, and the roots of that relationship probably predated the origin of the some 600 million years ago.

But now, we humans and our resident microbes are facing an unprecedented evolutionary situation, he said. First there was agriculture, which led to a radical change in the human diet, and then, more recently, the switch to an industrialized diet of refined foods. And in the 20th century we changed our internal ecology with antibiotics. Bacterial communities we've lived with for millennia are changing or breaking down, he said.

Several years ago, Knight was part of a study suggesting that delivering babies by caesarian section had the unintended consequence of changing their internal biota. In a small pilot study, he and researchers from the University of Puerto Rico found that vaginally delivered babies were colonized mostly by bacteria they picked up from mom on the trip out, while c-section babies were full of staph that had come from the environment.

Knight said he anticipates the ability to learn much more about our microscopic friends thanks to a $160 million effort to sequence their DNA known as the human microbiome project. By cataloging the microbial ecosystems of about 250 individuals, he said, scientists will be able to figure out what constitutes a normal mix of bacteria types and how our bacteria might signal disease.

Penn's Artis said there are a number of studies that connect microbial changes with diseases, including obesity, diabetes, asthma, and even possibly autism. In some cases where people have chronic infections such as hepatitis C, bacteria that belong in the have migrated out to the spleen and liver, he said, where they may be doing harm. There's also evidence that friendly microbes have migrated to harmful locations in people with a chronic digestive disorder known as inflammatory bowel disease. He considers these "good bugs gone bad."

By studying mice, he and collaborators have identified the immune cells that keep our good bugs from straying. Called innate lymphoid cells, they are part of the ancient that we share with insects and fish.

In a series of experiments, he and collaborators disabled those cells in mice and found that, indeed, helpful intestinal bacteria escaped to other parts of the body. That situation leads to chronic inflammation. The results were published last week in the journal Science as part of a special series devoted to our resident microbes.

Many interesting questions remain, including whether abnormalities in our bacterial colonies are causing disease, or whether conditions such as diabetes are disrupting our . We and our are in this together, our evolution forever linked to theirs.

Explore further: Good bugs gone bad: Gut immune cells keep beneficial microbes in their place

Related Stories

Good bugs gone bad: Gut immune cells keep beneficial microbes in their place

June 6, 2012
The healthy human intestine is colonized with over 100 trillion beneficial, or commensal, bacteria of many different species. In healthy people, these bacteria are limited to the intestinal tissues and have a number of helpful ...

Gut microbe makeup affected by diet: study

September 2, 2011
( -- A new study in the US has shown that the type of "good" bacteria that predominate in human stools varies with the diet.

Recommended for you

Magnetically applied MicroRNAs could one day help relieve constipation

January 17, 2018
Constipation is an underestimated and debilitating medical issue related to the opioid epidemic. As a growing concern, researchers look to new tools to help patients with this side effect of opioid use and aging.

Researchers devise decoy molecule to block pain where it starts

January 16, 2018
For anyone who has accidentally injured themselves, Dr. Zachary Campbell not only sympathizes, he's developing new ways to blunt pain.

Scientists unleash power of genetic data to identify disease risk

January 16, 2018
Massive banks of genetic information are being harnessed to shed new light on modifiable health risks that underlie common diseases.

Blood-vessel-on-a-chip provides insight into new anti-inflammatory drug candidate

January 15, 2018
One of the most important and fraught processes in the human body is inflammation. Inflammatory responses to injury or disease are crucial for recruiting the immune system to help the body heal, but inflammation can also ...

Molecule produced by fat cells reduces obesity and diabetes in mice

January 15, 2018
UC San Francisco researchers have discovered a new biological pathway in fat cells that could explain why some people with obesity are at high risk for metabolic diseases such as type 2 diabetes. The new findings—demonstrated ...

Obese fat becomes inflamed and scarred, which may make weight loss harder

January 12, 2018
The fat of obese people becomes distressed, scarred and inflamed, which can make weight loss more difficult, research at the University of Exeter has found.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jun 14, 2012
DVM Dermatologist has long recognized that Antibiotics / Poor Diet / NSAIDs / Illness > Severely Disrupt the delicate MicroBiome Balance / Health of our DOGs.

But many PET Parents Do Not Realize is that UnLess the GUT is Pro-Actively ReClaimed / ReSeeded & Repaired following Antibiotics .. the GUT is ReOccupied / Dominated by Pathogenic BAD Bacteria which not only compromises overall Absorb & BreakDown .. But over Time begin to compromise the GUT Lining Integrity > Leading to passage of "Stuff" into the Blood where it is Attacked > Leading to a LifeTime Slippery Slope of BAD Health.

To Address this Major Health Issue > Dr Kristin has Formulated GOO GUT RESCUE > Which RESCUE's Your DOG's GUT from Pathogenic BAD Bacteria > RESTORE's your animal's GUT with Beneficial Pre & Probiotic Strains > REPAIRs your Animal's GUT Lining / Integrity > RETAINs your animal's Beneficial MicroBiome AND RESOLVEs FOOD Issues related to 7 Provocative FOODs > Beef, Chicken, Lamb, Pork, Wheat, Corn & Soy.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.