The genus Lactobacillus currently contains over 180 species and encompasses a wide variety of organisms. Major species are L. casei group, and the species L. acidophilus, L. salivarius, and L. reuteri. They are a major part of the lactic acid bacteria group (i.e. they convert sugars to lactic acid). For human beings, they constitute a significant component of the microbiota of saliva and are responsible of acid production and low pH environment.