When you look at a carton of yogurt or a bottle of capsules, the probiotics listed are usually Lactobacillus acidophilus and possibly other lactobacilli along with one or more bifidobacterium species. However, a probiotic bacteria is any bacteria that is helpful to its host. Some help with digestion and some colonize to take up space that might be used by harmful bacteria. Some also make vitamins, and the friendly version of E. coli is one of these. You should not depend on your own bacteria to make enough of each vitamin to meet all your daily requirements, but they can help.
There are 2 types of natural vitamin K. K1 is made by plants. K2 in humans is made by bacteria in the large intestine and is essential for blood clotting. Your body can use both K1 and K2, and healthy people can get enough of these from their food and their own bacteria. Other forms of vitamin K are synthetic and are used medically as a substitute for the natural vitamins.
Biotin is considered one of the B complex vitamins. Its function in your body is to assist enzymes to metabolize fat and carbohydrates and to assimilate some amino acids. All life forms require biotin. It can only be formed by bacteria, yeasts, molds, algae and some plants. It has now been established that you can absorb some of the biotin made by your own intestinal bacteria.
Folic acid is another B complex vitamin that is produced by intestinal bacteria. Neural tube birth defects are associated with folic acid deficiency during pregnancy. Folic acid is essential for the synthesis of RNA and DNA as well as for the formation of red blood cells. A type of anemia results from deficiency of folic acid. This vital nutrient is abundant in leafy green vegetables.
Natural vitamin B12 is only made by bacteria. Your own probiotic bacteria produces some. You also can consume vitamin B12 made by bacteria in animals and distributed in their meat or milk. Its function in your body is the maturation of red blood cells and with folic acid in the folate form, to synthesize DNA. Deficiency results in a serious form of anemia.