Most species of this non-spore-forming bacterium ferment glucose into lactose, hence the name Lactobacillus. The most common application of Lactobacillus is industrial, specifically for dairy production. This genus also contains several bacteria that make up part of the natural flora of the GI tract and vagina. Because of their ability to derive lactic acid from glucose, these bacteria create an acidic environment which inhibits growth of many bacterial species which can lead to urogenital infections. Lactobacillus acidophilus (L. acidophilus) is the most commonly used probiotic, or "friendly" bacteria. Other potential probiotics include a variety of Lactobacillus species, such as the casei, GG, rhamnosus, NCFM, DDS-1, and johnsonii strains.

L. acidophilus preparations consist of dried or liquid cultures of living bacteria. These cultures are usually grown in milk but can sometimes be grown in milk-free cultures. L. acidophilus is available in freeze-dried granules, powders and capsules, and in liquid preparations, which must be kept refrigerated.

As with many other bacteria, it can be decimated by the use of antibiotics, and many health professionals recommend probiotics such as Lactobacillus to counter this side effect.