Lactobacillicus Acidophillus live primarily in the human's small intestines, mouth, and vagina. This bacteria can also be found in aminal disgestive tracts and in milk products, soil, air, and in animal stool. It has a normal pH of 3.5. This bacteria survives best at about 32 degrees celcius. The picture below shows the stomach, and below that the pink tubes that are squished together are the small intestine.