diacetylactis L. l. tructae Lactococcus lactis is a gram-positive bacterium used extensively in the production of buttermilk and cheese,[1] but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease.

[2] L. lactis cells are cocci that group in pairs and short chains, and, depending on growth conditions, appear ovoid with a typical length of 0.5 - 1.5 μm.

[5] Based on its history in food fermentation, L. lactis has generally recognized as safe (GRAS) status,[6][7] with few case reports of it being an opportunistic pathogen.

[11] Other uses that have been reported for this bacterium include the production of pickled vegetables, beer or wine, some breads, and other fermented foodstuffs like soymilk kefir, buttermilk, and others.

Bacteriophages specific to L. lactis cause significant economic losses each year by preventing the bacteria from fully metabolizing the milk substrate.

[27] The legislation was introduced in November 2009 as Assembly Bill 556 by Representatives Hebl, Vruwink, Williams, Pasch, Danou, and Fields; it was cosponsored by Senator Taylor.

It is suggested that the L. lactis supernatant mainly affects Salmonella motility through disruption of flagellar rotation rather than through irreversible damage to morphology and physiology.

Lactose fermentation by L. lactis produces acetate that reduces the intracellular pH of Salmonella, which in turn slows the rotation of their flagella.

[38] A study by Lothar Steidler and Wolfgang Hans[39] shows that in situ synthesis of IL-10 by genetically engineered L. lactis requires much lower doses than systemic treatments like antibodies to tumor necrosis factor (TNF) or recombinant IL-10.

Another route involves L. lactis being taken up by M cells because of its bacterial size and shape, and the major part of the effect may be due to recombinant IL-10 production in situ in intestinal lymphoid tissue.

In principle, this method may be useful for intestinal delivery of other protein therapeutics that are unstable or difficult to produce in large quantities and an alternative to the systemic treatment of IBD.