COLONIC MICROFLORA are the bacteria which reside in the large bowel of humans.
The human body, consisting of about 100 trillion cells, carries about ten times as many microorganisms in the intestinal tract. Bacteria make up most of the flora in the colon and 60% of the dry mass of faeces. Over 99% of the bacteria in the gut are anaerobes and live in the absence of oxygen.
Intestinal flora and humans have a mutually beneficial symbiotic relationship. Though people can survive without their large bowel flora (and some people do after surgery), the microorganisms perform many useful functions for the host.
These functions promote optimal health and include salvaging energy which would otherwise be lost in the faeces, reducing water loss, promoting normal immune function, preventing the growth of harmful bacteria, regulating the development of the gut, producing vitamins for the host (such as biotin and vitamin K), and producing hormones that help the host to store fats.