Lactococcus lactis
Encyclopedia
Lactococcus lactis is a Gram-positive
bacterium used extensively in the production of buttermilk
and cheese
, but has recently 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 typically 0.5 - 1.5 µm
in length. L. lactis does not produce spores (nonsporulating
) and are not motile (nonmotile
). They have a homofermentative metabolism and have been reported to produce exclusively 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. In general, it has been considered as an opportunistic pathogen, though the number of clinical cases associated with infections by these microorganisms has increased in the last decade in both humans and animals. L. 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.
, Camembert
, Cheddar
, Colby
, Gruyère
, Parmesan, and Roquefort. The state Assembly of Wisconsin
, the number one cheese-producing state in the United States
, voted in 2010 to name this bacterium as the official state microbe. It would have been the first and only such designation by a state legislature in the nation , however the legislation was not picked up by the Senate .
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 the phages mainly responsible for these losses are from the species 936
, c2, and P335 (all from the family Siphoviridae
).
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...
bacterium used extensively in the production of buttermilk
Buttermilk
Buttermilk refers to a number of dairy drinks. Originally, buttermilk was the liquid left behind after churning butter out of cream. It also refers to a range of fermented milk drinks, common in warm climates where unrefrigerated fresh milk otherwise sours quickly...
and cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....
, but has recently 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 typically 0.5 - 1.5 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
in length. L. lactis does not produce spores (nonsporulating
Endospore
An endospore is a dormant, tough, and temporarily non-reproductive structure produced by certain bacteria from the Firmicute phylum. The name "endospore" is suggestive of a spore or seed-like form , but it is not a true spore . It is a stripped-down, dormant form to which the bacterium can reduce...
) and are not motile (nonmotile
Motility
Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...
). They have a homofermentative metabolism and have been reported to produce exclusively 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. In general, it has been considered as an opportunistic pathogen, though the number of clinical cases associated with infections by these microorganisms has increased in the last decade in both humans and animals. L. 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
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
), from lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...
. The byproduct of ATP energy production is lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
. 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.
Cheese production
L. lactis subsp. lactis (formerly Streptococcus lactis) is used in the early stages for the production of many cheeses, including BrieBrie
Brie is a historic region of France most famous for its dairy products, especially Brie cheese. It was once divided into two sections ruled by different feudal lords: the western Brie française, corresponding roughly to the modern department of Seine-et-Marne in the Île-de-France region; the...
, Camembert
Camembert (cheese)
Camembert is a soft, creamy, surface-ripened cow's milk cheese. It was first made in the late 18th century in Normandy in northern France.-Production:...
, Cheddar
Cheddar cheese
Cheddar cheese is a relatively hard, yellow to off-white, and sometimes sharp-tasting cheese, produced in several countries around the world. It has its origins in the English village of Cheddar in Somerset....
, Colby
Colby cheese
-History:Joseph F. Steinwand in 1874 developed a new type of cheese at his father's cheese factory near Colby, Wisconsin. The cheese was named after the village, which had been founded three years earlier....
, Gruyère
Gruyère (cheese)
Gruyère is a hard yellow cheese, named after the town of Gruyères in Switzerland, and originated in the cantons of Fribourg, Vaud, Neuchâtel, Jura, and Berne...
, Parmesan, and Roquefort. The state Assembly of Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
, the number one cheese-producing state in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, voted in 2010 to name this bacterium as the official state microbe. It would have been the first and only such designation by a state legislature in the nation , however the legislation was not picked up by the Senate .
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 the phages mainly responsible for these losses are from the species 936
P008
P008 is a phage specific to Lactococcus lactis, an acid lactic bacterium used in the first stage of making cheese. P008 and related species are responsible for important loss each year in cheese factories....
, c2, and P335 (all from the family Siphoviridae
Siphoviridae
Siphoviridae are a family of double-stranded DNA viruses infecting only bacteria. The characteristic features of this family is the presence of a head and non contractile tail.There are at least 256 species in this family.-Virology:...
).