Gut Flora

The gut flora are the bacteria that normally live in the digestive tract and can perform a number of useful functions for their hosts. Also known as the intestinal microflora, the gut flora is made up of about 100 trillion bacteria, that is to say about ten times the number of cells the average human body consists of. There's an estimate of about 500 different bacterial species in the intestine. The metabolic activity performed by these bacteria is equal to that of a virtual organ making the gut bacteria termed as a forgotten organ.

The relationship between gut flora and humans is a mutualistic, symbiotic relationship. These microorganisms perform a host of useful functions, such as fermenting unused energy substrates, training the immune system, preventing growth of harmful species, regulating the development of the gut, producing vitamins for the host such as biotin and vitamin K, and producing hormones to direct the host to store fats. However, in certain conditions, some species are thought to be capable of causing disease or increasing cancer risk for the host.

Although the acid in the stomach, as well as bile and pancreatic secretions, hinder colonization of most bacteria in the stomach and proximal small intestine, most of the gut flora are found in the distal small intestine and in the cecum and ascending colon. In the small intestine there are Gram-positive cocci (bacteria), while those in the colon are mostly Gram-negative. The first part of the colon is mostly responsible for fermenting carbohydrates, while the latter part mostly breaks down proteins and amino acids. Bacterial growth is rapid.