''Lactococcus'' is a
genus of
lactic acid bacteria that were formerly included in the genus ''Streptococcus'' Group N1. They are known as homofermenters meaning that they produce a single product,
lactic acid in this case, as the major or only product of
glucose fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
. Their homofermentative character can be altered by adjusting environmental conditions such as
pH, glucose concentration, and nutrient limitation. They are
gram-positive,
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 t ...
-negative, non-
motile 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 chungangensis''
*''
Lactococcus formosensis''
*''
Lactococcus fujiensis''
*''
Lactococcus garvieae''
**''L. garvieae subsp. garvieae
**''L. garvieae subsp. bovis
*''
Lactococcus hircilactis''
*''
Lactococcus lactis''
**''L. lactis'' subsp. ''cremoris''
**''L. lactis'' subsp. ''hordniae''
**''L. lactis'' subsp. ''lactis''
**''L. lactis'' subsp. ''tructae''
*''
Lactococcus laudensis''
*''
Lactococcus nasutitermitis''
*''
Lactococcus piscium''
*''
Lactococcus plantarum''
*''
Lactococcus raffinolactis''
*''
Lactococcus taiwanensis''
These organisms are commonly used in the
dairy industry 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'' and ''
Streptococcus''. 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 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, respo ...
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
{{Taxonbar, from=Q134274
Streptococcaceae
Cheese
Bacteria genera