When most people think of bacteria, they picture disease-causing organisms and the need to fight infection. Although there are many types of harmful bacteria, the body contains many forms of helpful or "friendly" bacteria in the intestinal tract. Known as intestinal flora, these organisms consist of bacteria, fungi, protozoa and yeast, and have specific purposes that help the body.
The gastrointestinal tract is a complex system that allows the body to digest and absorb food while moving wastes for excretion. For the intestinal tract to function properly, normal flora must be present. Intestinal flora are types of microorganisms known as probiotics that live normally as part of the intestinal tract. These organisms have several functions that help the body, but also gain benefits from their hosts. For example, these microbes reside in the intestinal tract, where they receive nutrients for growth. Intestinal flora are found in both the large and small intestines.
Intestinal flora might aid in food digestion to form other components. For example, Lactobacillus acidophilus creates lactic acid and hydrogen peroxide in the intestine during the digestive process as it breaks down food, according to the University of Maryland Medical Center. The resulting products might serve other purposes as well, such as for immunity. Additionally, some intestinal flora might help with digestion by breaking down proteins or helping the body digest dairy products.
Some types of normal intestinal flora work to protect the body against certain kinds of infection. This may be through inhibiting the growth of harmful organisms that can cause infection. For example, Lactobacilli are intestinal flora and are considered "friendly" bacteria. These organisms inhibit the growth of Candida albicans, a type of yeast that can cause infection. Alternatively, some types of intestinal flora prevent infection by creating an intestinal barrier. For example, Bifidobacteria generate substances that restrain the growth of some types of gram-negative and gram-positive bacteria.
Not only do intestinal flora work to help the body break down and digest foods, they also are responsible for synthesizing some types of vitamins and nutrients. For example, normal intestinal flora help the body create vitamin K. They also provide assistance with mineral absorption and work to change some types of starches and sugars into sources of energy for the body.