Lactobacillus salivarius (L. salivarius) is a gram-positive, non-spore forming bacillus bacteria. It is a homofermentative organism (only produces one byproduct of metabolism—lactic acid) that is found occurring naturally in the human oral cavities, intestines, and vagina. It is considered to be non-pathogenic and is sometimes used to produce lactic acid in fermented foods and is used as a probiotic to help prevent infections by other microorganisms. L.salivarius also produces lactase enzyme as well as bacteriocins, proteins or peptides that are toxic to some other types of bacteria. While L.salivarius has been challenging to grow in culture for production purposes, it is quite prolific in the gut, and is therefore able to soon out compete many other bacteria, including many pathogens. L. salivarius is a facultative anaerobe, meaning that it can grow in the presence or absence of oxygen; it grows best in the small intestine, but the live bacteria can be found in feces as well. L. salivarius is somewhat unique among probiotics in that it is capable of growth in less than ideal conditions. It is one of only a few that can grow in high salt conditions. This makes L. salivarius an ideal probiotic for reducing the amounts of undesirable or pathogenic gut bacteria.