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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, meaning they produce lactic acid from sugars. They've also been reported to produce exclusive L-(+)-lactic acid. 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 it being an opportunistic pathogen.

Lactococcus 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, which then separates to form curds that 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 like 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.

L. 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 milk were lost, or down-regulated. This process, also called genome erosion or reductive evolution is also described in several other lactic acid bacteria. The proposed transition from the plant to the dairy environment was reproduced in the laboratory through experimental evolution of a plant isolate that was cultivated in milk for a prolonged period. Consistent with the results from comparative genomics (see references above) this resulted in L. lactis losing or down-regulating genes which are dispensable in milk and the up-regulation of peptide transport.

Hundreds of novel small RNAs were identified by Meulen et al. in the genome of L. lactis MG1363. One of them: LLnc147, was shown to be involved in carbon uptake and metabolism.


Effects of Heat-Killed Lactococcus lactis Strain Plasma on Skin Homeostasis-Related Genes and the Skin Microbiome among Healthy Adults: A Randomized Controlled Double-Blind Study Toshio Fujii, Takashi Fujitomo, Ryohei Tsuji, Ryuichi Kubo, Yukiko Kato, Osamu Kanauchi Microorganisms. 2021 Oct; 9(10): 2029. Published online 2021 Sep 25. doi: 10.3390/microorganisms9102029 PMCID: PMC8539941
The Effects of Dietary Supplementation of Lactococcus lactis Strain Plasma on Skin Microbiome and Skin Conditions in Healthy Subjects—A Randomized, Double-Blind, Placebo-Controlled Trial Ryohei Tsuji, Kamiyu Yazawa, Takeshi Kokubo, Yuumi Nakamura, Osamu Kanauchi Microorganisms. 2021 Mar; 9(3): 563. Published online 2021 Mar 9. doi: 10.3390/microorganisms9030563 PMCID: PMC8000884
Oral intake of heat-killed cells of Lactococcus lactis strain H61 promotes skin health in women Hiromi Kimoto-Nira, Reiji Aoki, Keisuke Sasaki, Chise Suzuki, Koko Mizumachi J Nutr Sci. 2012; 1: e18. Published online 2012 Dec 6. doi: 10.1017/jns.2012.22 PMCID: PMC4153081
PROBIOTICS - TYPES AND EFFECTS OF LACTIC ACID BACTERIA - AZ Sportivo Performance & AZSP Healing

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