Definition: A family of anaerobic to facultatively anaerobic, ordinarily nonmotile bacteria (order Eubacteriales) containing straight or curved, gram-positive rods that usually occur singly or in chains; motile cells are peritrichous. These organisms have complex organic nutritional requirements; they produce lactic acid from carbohydrates. They are found in fermenting animal and plant products where carbohydrates are available; they are also found in the mouth, vagina, and intestinal tract of various warm-blooded animals, including humans. Only a few species are pathogenic. The type genus is Lactobacillus, which contains 56 species.