Harmful Bacteria Live In Healthy Bodies Without Causing Disease

Depiction of the human body and bacteria that predominate     Larger Image at http://www.genome.gov/Images/press_photos/highres/20169-300.jpg(Photo credit: Wikipedia)

Somehow I always felt this to be true…

Many scientists now regard human bodies as “supra-organisms”, collections of communities made up of human and microbial cells coexisting in a whole that is more than the sum of its parts.

From the 14 June 2012 Medical News Today article

Scientists working on a huge project that has mapped all the different microbes that live in and on a healthy human body have made a number of remarkable discoveries, including the fact that harmful bacteria can live in healthy bodies and co-exist with their host and other microbes without causing disease.

This week sees the publication of several papers from the Human Microbiome Project (HMP), including two in Nature and two inPLoS ONE.

The Microbiome

The microbiome is the sum of all the microbes that colonize the body: it comprises trillions of microorganisms that outnumber human cells by 10 to 1. The microbes inhabit every nook and cranny of the body, and most of     the time the relationship is a friendly one, because they help digest food, strengthen the immune system and fight off dangerous pathogens.

Colorado University (CU)-Boulder Associate Professor Rob Knight of the BioFrontiers Institute is co-author on the two Nature papers. He told the press that the microbiome may only make up 1 to 3% of human body mass, but it plays a key role in human health.

One of the fascinating features of the microbiome is that different body sites have different communites of microorganisms that are as different from each other as the differences between microbial communities in oceans and deserts.

Knight said:

“By better understanding this microbial variation we can begin searching for genetic biomarkers for disease.”

Another of the curious features the HMP has discovered is that even healthy people carry low levels of harmful bacteria, but as long as the body remains healthy, they don’t cause disease, they just coexist alongside beneficial microbes. …

…

The HMP researchers established that more than 10,000 microbial species inhabit the human “ecosystem”. Knight said they believe they have now found between 81 and 99% of all genera of microorganisms in healthy adult Americans.

One of the key findings was the stark differences in microbial communities across the human body. For instance, the microbial communities that live on the teeth are different from those in saliva. …

…Another interesting discovery is that of the genes that influence human metabolism, most of them are in the microbiome and not in the human genome…

…gut bacteria do more than break down food and its constituents like proteins, fats and carbohydrates, they also produce beneficial compounds like vitamins and anti-inflammatories.

Related articles

• Human Microbiome Project Decodes Our 100 Trillion Good Bacteria (nytimes.com)

• Mutant Gut Bacteria Reverse Colon Cancer In Lab Models, UF Researchers Find (Medical News Today)
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