The ''Lactobacillaceae'' are a family of

lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bacte ...

. It is the only family in the lactic acid bacteria which includes homofermentative and heterofermentative organisms; in the ''Lactobacillaceae,'' the pathway used for hexose fermentation is a genus-specific trait. ''Lactobacillaceae'' include the homofermentative lactobacilli ''Lactobacillus'', ''Holzapfelia'', ''Amylolactobacillus'', ''Bombilactobacillus'', ''Companilactobacillus'', ''Lapidilactobacillus'', ''Agrilactobacillus'', ''Schleiferilactobacillus'', ''Loigolactobacillus'', ''Lacticaseibacillus'', ''Latilactobacillus'', ''Dellaglioa'', ''Liquorilactobacillus'', ''Ligilactobacillus'', and ''Lactiplantibacillus''; the heterofermentative lactobacilli ''Furfurilactobacillus'', ''Paucilactobacillus'', ''Limosilactobacillus'', ''Fructilactobacillus'', ''Acetilactobacillus'', ''Apilactobacillus'', ''Levilactobacillus'', ''Secundilactobacillus'', and ''Lentilactobacillus,'' which were previously classified in the genus ''

Lactobacillus ''Lactobacillus'' is a genus of Gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...

''; and the heterofermentative genera ''Convivina'', ''Fructobacillus'', ''Leuconostoc'', ''Oenococcus'', and ''Weissella'' which were previously classified in the ''Leuconostocaceae''. The ''Lactobacillaceae'' are also the only family of the lactic acid bacteria which does not include pathogenic or opportunistic pathogenic organisms although some species, particularly ''Lacticaseibacillus rhamnosus'' and ''Weissella'' spp. can cause rare infections in critically ill patients. With the exception of ''Lactococcus lactis'', ''Streptococcus thermophilus'' and ''Tetragenococcus halophilus'', most food fermenting lactic acid bacteria are now classified in the ''Lactobacillaceae''. The

grandfathered A grandfather clause, also known as grandfather policy, grandfathering, or grandfathered in, is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from t ...

term lactobacilli refers to all bacteria classified in Lactobacillaceae prior to 2020, i.e. ''Lactobacillus'' ''

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

'' (pre-split), ''

Pediococcus ''Pediococcus'' is a genus of gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera ''Aerococcu ...

'', and '' Sharpea''. Some authors use ''lactobacilli'' to refer to ''Lactobacillus'' ''sensu lato'' only.

Leuconostocaceae

At one point five genera (''Convivina'', ''Fructobacillus'', ''Leuconostoc'', ''Oenococcus'' and ''Weissella'') were considered a separate family called ''Leuconostocaceae''. These three genera are non-spore-forming, round or elongated in shape, and anaerobic or aerotolerant. They usually inhabit nutrient-rich environments such as milk, meat, vegetable products, and

fermented drink This is a list of fermented foods, which are foods produced or preserved by the action of microorganisms. In this context, Fermentation in food processing, fermentation typically refers to the fermentation of sugar to ethanol, alcohol using yeas ...

Lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natur ...

is the main end product of their characteristic heterofermentative carbohydrate metabolism. In 2020 Leuconostocaceae was synonymized with Lactobacillaceae.

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature o ...

and the phylogeny is based on whole-genome sequences.

References

Lactobacillales Bacteria families {{Lactobacilli-stub