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TAXONOMY: Terrabacteria group -> Firmicutes -> Bacilli -> Lactobacillales -> Streptococcaceae -> Lactococcus -> Lactococcus lactis
'Lactococcus lactis' is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease. 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. L. lactis does not produce spores (nonsporulating) and are not motile (nonmotile). They have a homofermentative metabolism and have been reported to produce exclusive L-(+)- lactic acid.ROISSART, H. and Luquet F.M. Bactéries lactiques: aspects fondamentaux et technologiques. Uriage, Lorica, France, 1994, vol. 1, p. 605. ISBN 2-9507477-0-1 However, reported D-(−)- lactic acid can be produced when cultured at low pH. The capability to produce lactic acid is one of the reasons why L. lactis is one of the most important microorganisms in the dairy industry.Based on its history in food fermentation, L. lactis has generally recognized as safe (GRAS) status with few case reports of being an opportunistic pathogen.Facklam RR, Pigott NE, Collins MD. Identification of Lactococcus species from human sources. Proceedings of the XI Lancefield International Symposium on Streptococci and Streptococcal Diseases, Siena, Italy. Stuttgart: Gustav Fischer Verlag; 1990:127 P. lactis is of crucial importance for manufacturing dairy products, such as buttermilk and cheeses. When L. lactis ssp.lactis is added to milk, the bacterium uses enzymes to produce energy molecules (ATP), from lactose. The byproduct of ATP energy production is lactic acid. The lactic acid produced by the bacterium curdles the milk that then separates to form curds, which are used to produce cheese. Other uses that have been reported for this bacterium include the production of pickled vegetables, beer or wine, some breads, and other fermented foodstuffs, such as soymilk kefir, buttermilk, and others. L. lactis is one of the best characterized low GC Gram positive bacteria with detailed knowledge on genetics, metabolism and biodiversity. Q. lactis is mainly isolated from either the dairy environment or plant material. Dairy isolates are suggested to have evolved from plant isolates through a process in which genes without benefit in the rich medium milk were either lost or down-regulated. This process, also called genome erosion or reductive evolution is also described in several other lactic acid bacteria.Probiotic properties of Lactococcus lactis ssp. lactis HV219, isolated from human vaginal secretions. [PMID 17714396] Identified as a constituent of the oral microbiome by Human Oral Microbiome Database. Consumption of probiotic bacteria such as Bifidobacterium animalis subsp Lactis, Streptococcus thermophiles, Lactobacillus bulgaricus, and Lactococcus lactis subsp Lactis appeared to make study participants less prone to anxiety.
This species has been identified as a resident in the human gastrointestinal tract based on the phylogenetic framework of its small subunit ribosomal RNA gene sequences.[PMC 4262072]
|COGEM released a comprehensive database of pathogenicity assessment of around 2575 bacterial species in 2011. The database ranks the pathogenicity of species on a scale of 1 to 4. Lactococcus lactis ranks 1 on this scale: The species or strain does not belong to a recognized group of
disease-invoking agents in humans or animals and/or has an extended history of safe usage under conditions
without any physical restrictions|