Editing Lactococcus lactis (section)

{{Short description|Species of bacterium}}
{{cs1 config|name-list-style=vanc}}
{{Speciesbox
| image = Lactococcus_lactis.jpg
| image_caption = 
| genus = Lactococcus
| species = lactis
| authority = ([[Joseph Lister, 1st Baron Lister|Lister]] 1873)<br/>Schleifer ''et al.'' 1986
| subdivision_ranks = Subspecies
| subdivision = ''L. l. cremoris''<br />
''L. l. hordniae''<br />
''L. l. lactis''<br />
''L. l. lactis bv. diacetylactis''<br />
''L. l. tructae''
}}

'''''Lactococcus lactis''''' is a [[gram-positive]] [[bacterium]] used extensively in the production of [[buttermilk]] and [[cheese]],<ref name="Brock">{{cite book |author= |title=Brock Biology of Microorganisms |publisher=Prentice Hall |year=2005 |isbn=978-0-13-144329-7 |editor-last=Madigan |editor-first=Michael T. |edition=11th |editor-last2=Martinko |editor-first2=John M.}}</ref> but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease.<ref>{{cite journal |vauthors=Braat H, Rottiers P, Hommes DW, Huyghebaert N, Remaut E, Remon JP, van Deventer SJ, Neirynck S, Peppelenbosch MP, Steidler L |title=A phase I trial with transgenic bacteria expressing interleukin-10 in Crohn's disease.|journal=Clin Gastroenterol Hepatol |volume=4 |issue=6 |pages=754–759 |year=2006|pmid=16716759 |doi=10.1016/j.cgh.2006.03.028 }}</ref> ''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&nbsp;[[micrometre|μm]]. ''L. lactis'' does not produce spores ([[Endospore|nonsporulating]]) and are not motile ([[Motility|nonmotile]]). They have a homofermentative metabolism, meaning they produce lactic acid from sugars. They've also been reported to produce exclusive <small>L</small>-(+)-[[lactic acid]].<ref>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}}</ref> However,<ref>{{cite journal |last1=Åkerberg |first1=C. |last2=Hofvendahl |first2=K. |last3=Zacchi |first3=G. |last4=Hahn-Hägerdal |first4=B. |year=1998 |title=Modelling the influence of pH, temperature, glucose and lactic acid concentrations on the kinetics of lactic acid production by Lactococcus lactis ssp. Lactis ATCC 19435 in whole-wheat flour |journal=Applied Microbiology and Biotechnology |volume=49 |issue=6 |pages=682–690 |doi=10.1007/s002530051232 |s2cid=46383610}}
</ref> reported <small>D</small>-(−)-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.<ref>[http://www.ebi.ac.uk/integr8/QuickSearch.do?action=doOrgSearch&organismName=Lactococcus+lactis Integr8 – Species search results:<!-- Bot generated title -->]</ref> Based on its history in food fermentation, ''L. lactis'' has [[generally recognized as safe]] (GRAS) status,<ref>{{cite web |url=https://www.fda.gov/Food/FoodIngredientsPackaging/GenerallyRecognizedasSafeGRAS/GRASSubstancesSCOGSDatabase/ucm084142.htm|archive-url=https://web.archive.org/web/20090709190627/http://www.fda.gov/Food/FoodIngredientsPackaging/GenerallyRecognizedasSafeGRAS/GRASSubstancesSCOGSDatabase/ucm084142.htm|url-status=dead|archive-date=July 9, 2009|title=History of the GRAS List and SCOGS Reviews |author=FDA |publisher=FDA |access-date=11 May 2012}}</ref><ref>{{cite journal |vauthors= Wessels S, Axelsson L, Bech Hansen E, De Vuyst L, Laulund S, Lähteenmäki L, Lindgren S, etal |title= The lactic acid bacteria, the food chain, and their regulation. |journal= Trends in Food Science & Technology |volume=15 |issue=10 |pages=498–505 |date=November 2004 |doi=10.1016/j.tifs.2004.03.003}}</ref> with few case reports of it being an opportunistic pathogen.<ref>{{cite journal |vauthors=Aguirre M, Collins MD |title=Lactic acid bacteria and human clinical infection |journal=Journal of Applied Bacteriology |volume=75 |issue=2 |pages=95–107 |date=August 1993 |pmid=8407678 |doi= 10.1111/j.1365-2672.1993.tb02753.x}}</ref><ref>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</ref><ref>{{cite journal |vauthors=Mannion PT, Rothburn MM |title=Diagnosis of bacterial endocarditis caused by Streptococcus lactis and assisted by immunoblotting of serum antibodies |journal=J. Infect. |volume=21 |issue=3 |pages=317–8 |date=November 1990 |pmid=2125626 |doi= 10.1016/0163-4453(90)94149-T}}</ref>

''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 ([[Adenosine triphosphate|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 [[curd]]s that are used to produce cheese.<ref>{{Cite web |title=Bacteria Genomes - LACTOCOCCUS LACTIS |url=http://www.ebi.ac.uk/2can/genomes/bacteria/Lactococcus_lactis.html |archive-url=https://web.archive.org/web/20080112035410/http://www.ebi.ac.uk/2can/genomes/bacteria/Lactococcus_lactis.html |archive-date=2008-01-12 |website=2Can Karyn's Genomes}}</ref> 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.<ref>{{Cite web |last1=Shurtleff |first1=William |last2=Aoyagi |first2=Akiko |date=2004 |title=History of Fermented Soymilk and Its Products |url=https://www.soyinfocenter.com/HSS/fermented_soymilk.php |access-date=2024-01-14 |website=www.soyinfocenter.com}}</ref> ''L. lactis'' is one of the best characterized low GC Gram positive bacteria with detailed knowledge on genetics, metabolism and biodiversity.<ref>{{cite journal |vauthors= Kok J, Buist G, Zomer AL, van Hijum SA, Kuipers OP |title= Comparative and functional genomics of lactococci. |journal= FEMS Microbiology Reviews |volume=29 |issue=3 |pages=411–33 |year=2005 |pmid=15936843|doi= 10.1016/j.femsre.2005.04.004|doi-access=free }}</ref><ref name="van2006">{{cite journal |vauthors=van Hylckama Vlieg JE, Rademaker, JL, Bachmann H, Molenaar D, Kelly WJ, Siezen RJ |title=Natural diversity and adaptive responses of ''Lactococcus lactis'' |journal=Current Opinion in Biotechnology| volume=17 |issue=2 |pages=183–90 |year=2006 |doi=10.1016/j.copbio.2006.02.007 |pmid=16517150}}</ref>

''L. lactis'' is mainly isolated from either the dairy environment, or plant material.<ref>{{cite journal|vauthors=Kelly WJ, Ward LJ, Leahy SC |title=Chromosomal diversity in Lactococcus lactis and the origin of dairy starter cultures.|journal=Genome Biology and Evolution| volume=2|pages=729–44|year=2010| doi=10.1093/gbe/evq056|pmid=20847124|pmc=2962554}}</ref><ref>{{cite journal|vauthors=Passerini D, Beltramo C, Coddeville M, Quentin Y, Ritzenthaler P, Daveran-Mingot ML, Le Bourgeois P |title=Genes but Not Genomes Reveal Bacterial Domestication of Lactococcus Lactis.|journal=PLOS ONE| volume=5|issue=12|pages=e15306|year=2010| doi=10.1371/journal.pone.0015306|pmid=21179431|pmc=3003715|bibcode=2010PLoSO...515306P|doi-access=free}}</ref><ref>{{cite journal|vauthors=Rademaker JL, Herbet H, Starrenburg MJ, Naser SM, Gevers D, Kelly WJ, Hugenholtz J |title= Diversity analysis of dairy and nondairy Lactococcus lactis isolates, using a novel multilocus sequence analysis scheme and (GTG)5-PCR fingerprinting.|journal=Applied and Environmental Microbiology|volume=73|issue=22|pages=7128–37|year=2007| doi=10.1128/AEM.01017-07|display-authors=etal|pmid=17890345|pmc=2168189|bibcode= 2007ApEnM..73.7128R}}</ref> 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 downregulated.<ref name="van2006"/><ref>{{cite journal|vauthors=Siezen RJ, Starrenburg MJ, Boekhorst J, Renckens B, Molenaar D, van Hylckama Vlieg JE |title=Genome-scale genotype-phenotype matching of two ''Lactococcus lactis'' isolates from plants identifies mechanisms of adaptation to the plant niche.|journal=Applied and Environmental Microbiology| volume=74|issue=2|pages=424–36|year=2008| doi=10.1128/AEM.01850-07|pmid=18039825|pmc=2223259|bibcode=2008ApEnM..74..424S}}</ref> This process, called genome erosion or [[reductive evolution]], has been described in several other [[lactic acid bacteria]].<ref>{{cite journal|vauthors=Bolotin A, Quinquis B, Renault P, Sorokin A, Ehrlich SD, Kulakauskas S, Lapidus A, etal |title=Complete sequence and comparative genome analysis of the dairy bacterium ''Streptococcus thermophilus''.|journal=Nature Biotechnology| volume=22|issue=12|pages=1554–8|year=2004| doi=10.1038/nbt1034|pmid=15543133|pmc=7416660|doi-access=free}}</ref><ref>{{cite journal|vauthors=van de Guchte M, Penaud S, Grimaldi C, Barbe V, Bryson K, Nicolas P, Robert C |title=The complete genome sequence of ''Lactobacillus bulgaricus'' reveals extensive and ongoing reductive evolution.|journal=Proceedings of the National Academy of Sciences of the United States of America| volume=103|issue=24|pages=9274–9|year=2006| doi=10.1073/pnas.0603024103|display-authors=etal|pmid=16754859|pmc=1482600|bibcode=2006PNAS..103.9274V|doi-access=free}}</ref> 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 downregulating genes that are dispensable in milk and the upregulation of peptide transport.<ref>{{cite journal|vauthors=Bachmann H, Starrenburg MJ, Molenaar D, Kleerebezem M, van Hylckama Vlieg JE |title=Microbial domestication signatures of ''Lactococcus lactis'' can be reproduced by experimental evolution.|journal=Genome Research| volume=22|issue=1|pages=115–24|year=2012| doi=10.1101/gr.121285.111|pmid=22080491|pmc=3246198}}</ref>

Hundreds of novel [[small RNA]]s 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]].<ref>{{Cite journal|last1=Meulen|first1=Sjoerd B. van der|last2=Jong|first2=Anne de|last3=Kok|first3=Jan|date=2016-03-03|title=Transcriptome landscape of Lactococcus lactis reveals many novel RNAs including a small regulatory RNA involved in carbon uptake and metabolism|journal=RNA Biology|volume=13|issue=3|pages=353–366|doi=10.1080/15476286.2016.1146855|issn=1547-6286|pmid=26950529|pmc=4829306}}</ref>