While Acidophilus serves the small intestines, Bifidus is the friendly bacteria for the large intestine. As the digestive system's primary "mover and shaker", the large intestine reabsorbs the water from our food and passes the remaining waste out of the body. When it functions properly, the large intestine can help prevent gas, bloating and diarrea. Bifidus helps repopulate the large intestine with friendly bacteria, restoring the healthful environment it needs to do its job well.