NEWS of The Controversy between evolution and creationism is scarce today, so in our never-ending quest to bring you timely and tasteful information, we present to you, dear reader, some excerpts from Caltech Biologists Link Gut Microbial Equilibrium to Inflammatory Bowel Disease, a press release from the California Institute of Technology. The bold font was added by us:
We are not alone — even in our own bodies. The human gut is home to 100 trillion bacteria, which, for millions of years, have co-evolved along with our digestive and immune systems.
Great introduction! Let’s read on:
Most people view bacteria as harmful pathogens that cause infections and disease. Other, more agreeable, microbes (known as symbionts) have taken a different evolutionary path, and have established beneficial relationships with their hosts. Still other microbes may be perched somewhere in between, according to research by biologists at the California Institute of Technology (Caltech) that offers new insight into the causes of inflammatory bowel disease (IBD) and colon cancer.
A paper about their work appears in the April 22 issue of the journal Cell Host & Microbe.
Here’s the abstract: A Pathobiont of the Microbiota Balances Host Colonization and Intestinal Inflammation. We continue with the press release:
“It has been proposed that the coupled equilibrium between potentially harmful and potentially beneficial bacteria in the gut mediates health versus disease,” says Sarkis K. Mazmanian, assistant professor of biology at Caltech. “If the balance is altered,” say, by changes in diet, the effects of stress, or the use of antibiotics, “then the immune response in the intestines is also changed.” This altered host–microbe relationship, called dysbiosis, has been linked to IBD and colon cancer as well as to obesity and diabetes.
The message is clear: Avoid dysbiosis. Here’s more:
Close to a thousand different species of bacteria reside in the gut, which makes understanding the consequences of dysbiosis a challenge.
A thousand different species! Your Curmudgeon is exceedingly pleased to host such diversity. Moving along:
One way of studying the effects of a balanced host–microbe relationship, and how it arises in the first place, is to change experimentally the relative population size of the microbe. That’s exactly what Mazmanian and graduate student Janet Chow accomplished in a bacterium called Helicobacter hepaticus.
We don’t want anyone messing around with our host–microbe relationship. It’s working just fine — as it has evolved to do. Another excerpt:
Helicobacter hepaticus has an unusual modus operandi.
You can say that again! We’ll skip the next few paragraphs, and then:
“The bacteria appear to have struck a deal with their host,” Mazmanian says [Sarkis K. Mazmanian, assistant professor of biology at Caltech]. They keep their own numbers low so they don’t overwhelm the immune system, and in return, the immune system leaves them alone. “The bacteria need the secretion system to put the host in ‘don’t attack’ mode.” In return, the presence of the bacteria does not induce inflammation, as would be the case with a pathogen that has not evolved a similar “agreement.”
A most sensible arrangement. And now we come to the end:
“There has to be communication. It could be peaceful — as is the case for symbionts—or it could be an argument—as is the case for pathogens. But when this molecular dialogue breaks down, it’s probably harmful to both microbe and man,” Mazmanian says.
Disrupt that communication, and the balance gets thrown out of whack. “Inflammation leads to cancer, and this bacterium has been associated with inflammation and colon cancer in animals,” he says. Understanding if dysbiosis causes disease in humans could lead to therapies based on restoring the healthy microbial balance in the gut.
We fervently hope that the little fellows we’re hosting continue to maintain all needful lines of communication. The alternative is much too … disruptive to contemplate.
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