Microbial Interaction

We may think of ourselves as a highly evolved species of conscious individuals, but we are all far less human than most of us appreciate. Scientists have long recognized that the bacterial cells inhabiting our skin and gut outnumber human cells by ten-to-one.

Indeed, Princeton University scientists compared the approximately 30,000 human genes found in the average human to the more than 3 million bacterial genes inhabiting us, concluding that we are at most one percent human. We are only beginning to understand the sort of impact our bacterial companions have on our daily lives.

Moreover, these bacteria have been implicated in the development of neurological and behavioral disorders. For example, gut bacteria may have an influence on the body=s use of vitamin B6, which in turn has profound effects on the health of nerve and muscle cells. They modulate immune tolerance and, because of this, they may have an influence on autoimmune diseases, such as multiple sclerosis.

They have been shown to influence anxiety-elated behavior, although there is controversy regarding whether gut bacteria exacerbate or ameliorate stress related anxiety responses. In autism and other pervasive developmental disorders, there are reports that the specific bacterial species present in the gut are altered and that gastrointestinal problems exacerbate behavioral symptoms. A newly developed biochemical test for autism is based, in part, upon the end products of bacterial metabolism.

Regardless of how these intestinal guests exert their influence, these studies suggest that brain-directed behaviors, which influence the manner of interaction with the external world, may be deeply influenced by the relationship with the microbial organisms living in the gut. And the discovery that gut bacteria exert their influence on the brain may have important implications for developmental brain disorders.  Read more…