Friday, May 11, 2012

Native bacteria fight off intruders in the gut

Our bodies are home to many bacteria. In fact, there are more bacteria in our body than cells, which could make one consider human beings as mere hosts for microbes, instead of independently operating organisms. We find most of the bacteria in our gut, where they help with food digestion. It is a form of symbiosis, meaning mutual benefit, even though it would be disastrous if the bacteria end up in our bloodstream, as they would cause major infection and possibly even death. While sitting in our gut, bacteria fend off  'foreign' microbes, and scientists have revealed how this happens, which sheds light on how certain infections occur.

Native bacteria
There are about a thousand different bacterial species living in our gut, each of them leaving us unharmed when left in their natural habitat. In fact, we cannot do without them, as they are needed to correctly process our food, rendering us able to utilize the nutrients. Each human being has its own unique set of gut bacteria, even though there are about three main patterns to distinguish. Of those three, each one has its own characteristics, and it influences the way the gut functions. The set of bacteria you have can also be a factor for health problems, which makes assessing characteristics of the bacterial population an important factor when diagnosing gastro-intestinal diseases.

Every day, our body is exposed to the outside world in which bacteria are swarming around. One of the ways of getting in is through the digestive tract, but native bacteria make sure there is a healthy dose of competition for the available space. Sometimes, invaders do manage to populate the gut, causing health problems and disease. Scientists from the University of Michigan have discovered what makes foreign bacteria successful when invading our gut, and it has something to do with genes.

In an effort to gain a permanent spot in the gut, invading bacteria turn on so-called virulence genes, which allows for the production of proteins that help them attach to the cellular lining of the gut. By doing this, they gain a permanent spot, and are able to get food and reproduce themselves, outperforming the native bacteria. This results in inflammation and diarrhea, and that means the pathogens have achieved their goal. Consequently, their offspring let go of the cells they were attached to. It means they end up in the patient's faeces, allowing for more spread in the case of bad hygiene situations.
Bacteria attaching themselves to the gut lining. Left: bacteria are stained yellow, while tissue is stained blue. Right: close-up of bacteria attaching themselves.
Even though proper sanitation is the most important to prevent spread of these bacterial infections, the scientists argue it is helpful to know how pathogens function. If we can find a way to prevent them from expressing virulence genes, it may be possible to prevent certain bacterial infections. Scientists are going to experiment with different sugars in our diet, to assess whether leaving them out can reduce the success rate for pathogenic bacteria. 

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