Lactococcus lactis

Taxobox
color = lightgrey
name = "Lactococcus lactis"

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image_width = 250px
image_caption =
regnum = Bacteria
divisio = Firmicutes
classis = Bacilli
ordo = Lactobacillales
familia = Streptococcaceae
genus = "Lactococcus"
species = "L. lactis"
binomial = "Lactococcus lactis"
binomial_authority = (Lister 1873)
Schleifer "et al." 1986
subdivision_ranks = Subspecies
subdivision = "L. l. cremoris"
"L. l. hordniae"
"L. l. lactis"
"L. l. lactis bv. diacetylactis"

"Lactococcus lactis" is a Gram-positive bacteria used extensively in the production of buttermilk and cheese.cite book | author = Madigan M, Martinko J (editors). | title = Brock Biology of Microorganisms | edition = 11th ed. | publisher = Prentice Hall | year = 2005 | isbn = 0-13-144329-1 ] "L. lactis" are cocci that group in pairs and short chains,and depending on growth conditions appears ovoid with typically 0.5 - 1.5 µm in length. "L. lactis" do not produce spores (non-sporulating) and are not motile (non-motile). Cultured in the laboratory, "L. lactis" colonies appear bright orange on nutrient agar. They have a homo-fermentative metabolism and have been reported to produce exclusively 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, [AKERBERG, C.; HOFVENDAHL, K.; ZACCHI, G. and HAHN-HAGERDAL, B. Modeling the influence of pH, temperature, glucose and lactic acid concentration on the kinetics of lactic acid production by "Lactococcus lactis" ssp. lactis ATCC 19435 in whole-wheat flour. Applied Microbiology and Biotechnology, 1998, vol. 49, no. 6, p. 682-690] reported that D(-) lactic acid can be produced when cultured at low pH. The capability to produce lactic acid is one of the reasons why "Lactococcus lactis" is one of the most important micro-organisms involved in the dairy industry [ [http://www.ebi.ac.uk/integr8/QuickSearch.do?action=doOrgSearch&organismName=Lactococcus+lactis Integr8 - Species search results: ] ] . Generally, it has been considered as an opportunistic pathogen [Aguirre M, Collins MD. Lactic acid bacteria and human clinical infection. J Appl Bacteriol 1993;75:95-107] . Even though, the number of clinical cases associated with infections by these microorganisms has increased in the last decade in both humans and animals [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] [Mannion PT, Rothburn MM. Diagnosis of bacterial endocarditis caused by Streptococcus lactis and assisted by immunoblotting of serum antibodies. J Infect 1990;21:317-8] . "L. lactis" is a bacterium which has a crucial importance for manufacturing dairy products such as buttermilk, yogurt or cheese. When "L. lactis" ssp. lactis is added to milk, the bacterium uses enzymes to produce energy molecules, called 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 and whey [ [http://www.ebi.ac.uk/2can/genomes/bacteria/Lactococcus_lactis.html Lactococcus_lactis ] ] .

Other uses that have been reported for this bacteria include the production of pickled vegetables, beer or wine, some breads and other fermented food-stuffs such as soymilk kefir, buttermilk, ... [ [http://www.soyinfocenter.com/HSS/fermented_soymilk.php Lactococcus lactis uses] ] . Nowadays, researchers believe that understanding the physiology and genetic make-up of this bacterium will provide food manufacturers as well as the pharmaceutical industry with invaluables benefits [ [http://www.genoscope.cns.fr Site du Genoscope ] ] [Steidler L, Rottiers P., Therapeutic drug delivery by genetically modified Lactococcus lactis, Ann N Y Acad Sci 2006; 1072, 176-186]

Cheese production

"L. lactis" subsp. "lactis" (formerly "Streptococcus lactis" [cite journal |author=Chopin MC, Chopin A, Rouault A, Galleron N |title=Insertion and amplification of foreign genes in the Lactococcus lactis subsp. lactis chromosome |journal=Appl. Environ. Microbiol. |volume=55 |issue=7 |pages=1769–74 |year=1989 |pmid=2504115 |url=http://aem.asm.org/cgi/reprint/55/7/1769?view=long&pmid=2504115 | format = PDF] ) is used in the early stages for the production of many cheeses including Brie, Camembert cheese, cheddar, Colby, Gruyère, Parmesan, and Roquefort.cite journal | author=Coffey A, Ross RP | title=Bacteriophage-resistance systems in dairy starter strains: molecular analysis to application | journal=Antonie Van Leeuwenhoek | year=2002 | pages=303–21 | volume=82 | issue=1–4 | pmid=12369198 | doi=10.1023/A:1020639717181]

The use of "L. lactis" in dairy factories is not without issues. Bacteriophages specific to "L. lactis" cause significant economic losses each year by preventing the bacteria from fully metabolizing the milk substrate. Several epidemiologic studies showed that the phages mainly responsible for these losses are from the species "936", "c2" and "P335".cite journal | author=Madera C, Monjardin C, Suarez JE | title=Milk contamination and resistance to processing conditions determine the fate of "Lactococcus lactis" bacteriophages in dairies | journal=Appl Environ Microbiol | year=2004 | pages=7365–71 | volume=70 | issue=12 | pmid=15574937 | url=http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=535134&blobtype=pdf | format=PDF | doi=10.1128/AEM.70.12.7365-7371.2004]

References