The digestive tract is the home to a majority of the human microbiota of our body. The gastrointestinal system is just one of the niches of the human body that these microbes live in. The human gut is colonized by 1014 microorganisms which is approximately ten times the number of human cells! The human gut consists of approximately 300-500 species of bacteria. The stomach and small intestine contain very little bacteria due to the hostile environment in the lumen, namely presence of acid, bile and pancreatic fluid which destroy most bacteria. Additionally, because the propulsive movements push the luminal contents towards the colon, the capacity for bacteria to colonize the stomach and small intestine is limited. However, the colon is host to numerous species of bacteria in high numbers. Though some of these may be potentially disease causing, many of them offer untold benefits to the human host.
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