Lactobacillus acidophilus (meaning acid-loving milk-bacterium) is a species in the genus Lactobacillus. L. acidophilus is a homo-fermentative species, fermenting sugars into lactic acid, which grows readily at rather low pH values (below pH 5.0) and has an optimum growth temperature of 30 Â°C (86 Â°F). L. acidophilus occurs naturally in the human and animal gastrointestinal tract, mouth, and vagina. Some strains of L. acidophilus may be considered to have probiotic characteristics. These strains are commercially used in many dairy products, sometimes together with S. salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in the production of acidophilus-type yogurt.