There are several varieties of bacteria that thrive in acid environments. These include Bifidus (mother''s milk bacteria) and Acidophilus (healthy intestinal bacteria). These are helpful in digestive upsets, as treatments for certain vaginal disorders, and as treatments in skin care.Acidophilus is lactic bacteria that are one-celled micro-organisms essential in the digestive tract for performing many functions necessary to promote immunity and proper nutrition. (Read Acidophilus More Info..)