Lactococcus lactis

Lactococcus lactis are bacteria that live on plants, animal skin and hair. They are also used extensively in the production of buttermilk and cheese because they curdle and perfume milk.

Lactococcus lactis are nonsporulating, nonmotile, Gram-positive cocci that group in pairs and short chains. Their typical size is 0.5 - 1.5 µm in length. When fermenting milk, they produce large quantities of lactic acid.

Lactococcus lactis subsp. lactis is used in the early stages for the production of the following cheeses: Brie, Camembert, cheddar, Colby, Gruyère, Parmesan and Roquefort.

The use of Lactococcocus lactis in diary factories is not without issues. Phages specific to Lactococcus lactis are causing important losses each year by preventing the bacteria from taking over the milk subsrate. Several epidemiologic studies showed that the phages mainly responsible for these losses are from the species 936, c2 and P335.