The mammalian lower intestine contains up to 10¹² bacteria per gram of intestine. The normal microbiota* are essential to maintain appropriate homeostatic (balanced) conditions, providing energy in form of short-chain fatty acids and nutrients like vitamins K and B12., and protection against colonization by pathogenic bacteria. The bacterial flora accounts in great parts for the maturation of our immune system. They are tightly intertwined with the mucosal lining of the gut.
And we should not forget about the fact that the first sip we take in life consists of billions of bacteria. And we survive. So, they accompany us from the very beginning of our life without doing us any harm.And bacteria make up most of the flora in the colon and 60% of the dry mass of feces. Somewhere between 300 and 1000 different species live in the gut, with most estimates at about 500. However, it is probable that 99% of the bacteria come from about 30 or 40 species. Fungi and protozoa also make up a part of the gut flora, but little is known about their activities.
If this microenvironment is loosing its balance than the way for infections may be paved. Typical is the increase of shingles in elderly people partly due to an imbalance and loss of bacterial activities in the gut’s flora. Our gut is such a powerful organ, we should care about it a lot.
*The microorganisms that typically inhabit a bodily organ or part; flora
Source: Fujihashi K, Kiyono H: Mucosal immunosenescence: new developments and vaccines to control infectious diseases. Trends in Immunol. July 2009 Vol. 30:7, 334-343
