Lactobacillus is a genus of gram-positive bacteria within the Lactobacillaceae family. Members of the genus are aerotolerant anaerobes or microaerophilic, rod-shaped, and do not form endospores. Until 2020, the genus Lactobacillus comprised 261 phylogenetically, ecologically, and metabolically diverse species; a taxonomic revision of the genus reassigned many former Lactobacillus species to 25 genera (see § Taxonomy below).
Lactobacillus species constitute a significant component of the human and animal microbiota at a number of body sites, such as the digestive system and female genital system. Lactobacillus species are normally a major part of the vaginal microbiota. Lactobacillus forms biofilms in the vaginal and gut microbiota, allowing them to persist in harsh environmental conditions and maintain ample populations. Lactobacillus exhibits a mutualistic relationship with the human body, as it protects the host against potential invasions by pathogens, and in turn, the host provides a source of nutrients. Lactobacilli are among the most common probiotics found in food such as yogurt, and the bacteria are diverse in their application in maintaining well-being, by helping to treat diarrhea, vaginal infections, and skin disorders such as eczema.
Metabolism
Lactobacilli are homofermentative, i.e., hexoses are metabolized by glycolysis to lactate as the major end product, or heterofermentative, i.e., hexoses are metabolized by the phosphoketolase pathway to lactate, CO2, and acetate or ethanol as major end products. Most lactobacilli are aerotolerant and some species respire if heme and menaquinone are present in the growth medium. Aerotolerance of lactobacilli is manganese-dependent and has been explored (and explained) in Lactiplantibacillus plantarum (previously Lactobacillus plantarum). Lactobacilli generally do not require iron for growth.
The Lactobacillaceae are the only family of the lactic acid bacteria (LAB) that includes homofermentative and...
