Lactococcus

Lactococcus, from Latin lac, meaning "milk", and Ancient Greek κόκκος (kókkos), meaning "berry", is a genus of lactic acid bacteria that were formerly classified as Lancefield group N streptococci. They are known as homofermenters meaning that they produce a single product, lactic acid in this case, as the major or only product of glucose fermentation. Their homofermentative character can be altered by adjusting environmental conditions such as pH, glucose concentration, and nutrient limitation. They are gram-positive, catalase-negative, non-motile cocci that are found singly, in pairs, or in chains. The genus contains strains known to grow at or below 7˚C.

Taxonomy

The type species of the genus is Lactococcus lactis. The List of Prokaryotic names with Standing in Nomenclature (LPSN) recognizes 16 species with validly published and correct names in Lactococcus:

Lactococcus intestinalis is treated as a later heterotypic synonym of L. muris.

A genome-based revision divided the genus into two phylogenetic groups and introduced the genus Pseudolactococcus for one of them. Although Pseudolactococcus was validly published, LPSN currently treats it as a heterotypic synonym of Lactococcus.

Uses

These organisms are commonly used in the dairy industry in the manufacture of fermented dairy products such as cheeses. They can be used in single-strain starter cultures, or in mixed-strain cultures with other lactic acid bacteria such as Lactobacillus and Streptococcus.