''Lactococcus'', from Latin 'lac', meaning "milk", and
Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
κόκκος (''kókkos''), meaning "sphere", is a
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
lactic acid bacteria
Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...
that were formerly included in the genus ''Streptococcus'' Group N1. They are known as homofermenters meaning that they produce a single product,
lactic acid
Lactic acid is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as wel ...
in this case, as the major or only product of
glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
fermentation
Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...
. Their homofermentative character can be altered by adjusting environmental conditions such as
pH, glucose concentration, and nutrient limitation. They are
gram-positive
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
The Gram stain is ...
,
catalase
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...
-negative, non-
motile
Motility is the ability of an organism to move independently using metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components.
Motility is observed in animals, mi ...
cocci that are found singly, in pairs, or in chains. The genus contains strains known to grow at or below 7˚C.
Twelve species of ''Lactococcus'' are currently recognized. They are:
*''
Lactococcus allomyrinae''
*''
Lactococcus carnosus''
*''
Lactococcus chungangensis''
*''
Lactococcus cremoris''
**''L. cremoris'' subsp. ''cremoris''
**''L. cremoris'' subsp. ''tructae''
*''
Lactococcus formosensis''
**''L. formosensis'' subsp. ''bovis''
**''L. formosensis'' subsp. ''formosensis''
*''
Lactococcus fujiensis''
*''
Lactococcus garvieae''
**''L. garvieae'' subsp. ''garvieae''
**''L. garvieae'' subsp. ''bovis''
*''
Lactococcus hircilactis''
*''
Lactococcus hodotermopsidis''
*''
Lactococcus insecticola''
*''
Lactococcus kimchii''
*''
Lactococcus lactis''
**''L. lactis'' subsp. ''hordniae''
**''L. lactis'' subsp. ''lactis''
*''
Lactococcus laudensis''
*''
Lactococcus nasutitermitis''
*''
Lactococcus paracarnosus''
*''
Lactococcus petauri''
*''
Lactococcus piscium''
*''
Lactococcus plantarum''
*''
Lactococcus protaetiae''
*''
Lactococcus raffinolactis''
*''
Lactococcus reticulitermitis''
*''
Lactococcus taiwanensis''
*''
Lactococcus termiticola''
These organisms are commonly used in the
dairy industry
A dairy is a place where milk is stored and where butter, cheese, and other dairy products are made, or a place where those products are sold. It may be a room, a building, or a larger establishment. In the United States, the word may also des ...
in the manufacture of fermented dairy products such as cheeses. They can be used in single-strain starter cultures, or in mixed-strain cultures with other lactic acid bacteria such as ''
Lactobacillus
''Lactobacillus'' is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...
'' and ''
Streptococcus
''Streptococcus'' is a genus of gram-positive spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occurs along a sing ...
''. Special interest is placed on the study of ''L. lactis'' subsp. ''lactis'' and ''L. lactis'' subsp. ''cremoris'', as they are the strains used as starter cultures in industrial dairy fermentations. Their main purpose in dairy production is the rapid acidification of milk; this causes a drop in the pH of the fermented product, which prevents the growth of spoilage bacteria. The bacteria also play a role in the flavor of the final product.
Lactococci are currently being used in the
biotechnology
Biotechnology is a multidisciplinary field that involves the integration of natural sciences and Engineering Science, engineering sciences in order to achieve the application of organisms and parts thereof for products and services. Specialists ...
industry. They are easily grown at industrial scale on whey-based media. As food-grade bacteria, they are used in the production of foreign
proteins
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, re ...
that are applied to the food industry.
Diseases
Lactococcosis refers to a group of disorders caused by the bacterium
L. garvieae. Most "Lacto" species dwell on the bodies of humans and animals, and while they do not cause serious problems in higher animals, they do cause chronic illnesses in lower animals, particularly fish.
[Rao, S, Chen, M-Y, Sudpraseart, C, et al. Genotyping and phenotyping of Lactococcus garvieae isolates from fish by pulse-field gel electrophoresis (PFGE) and electron microscopy indicate geographical and capsular variations. J Fish Dis. 2022; 45: 771– 781. https://doi.org/10.1111/jfd.13601]
References
{{Authority control
Bacteria used in dairy products
Streptococcaceae
Cheesemaking
Bacteria genera