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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. Their homofermentative character can be altered by adjusting environmental conditions such as pH, glucose concentration, and nutrient limitation. They are gram-positive, catalase-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.
Lactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has 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 a typical length of 0.5 - 1.5 µm. L. lactis does not produce spores (nonsporulating) and are not motile (nonmotile). They have a homofermentative metabolism, meaning they produce lactic acid from sugars. They've also been reported to produce exclusive 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. Based on its history in food fermentation, L. lactis has generally recognized as safe (GRAS) status with few case reports of being an opportunistic pathogen.
Viili (Finnish) is a mesophilic fermented milk product found in Finland. This cultured milk beverage is the results of microbial action of lactic acid bacteria (LAB) and a surface-growing yeast-like fungus Geotrichum candidum present in milk, which forms a velvet-like surface on viili. In addition, most traditional viili cultures also contain yeast strains such as Kluveromyces marxianus and Pichia fermentans. The lactic acid bacteria identified in viili include the acid‐producing Lactococcus lactis subsp. lactis and L. l. cremoris as well as the aroma producers L. lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteroides. Among those mesophilic LAB strains, the slime-forming Lc. lactis subsp. cremoris produce a phosphate-containing heteropolysaccharide, named viilian. Viilian is similar to kefiran produced by kefir grains. The production of exopolysaccharides (EPS) by the strain forms the consistency character of viili and it has been claimed to have various functional benefits toward the rheological properties of milk products and the health improving potential.
Fermented milk products or fermented dairy products, also known as cultured dairy foods, cultured dairy products, or cultured milk products, are dairy foods that have been fermented with lactic acid bacteria such as Lactobacillus, Lactococcus, and Leuconostoc. The fermentation process increases the shelf life of the product while enhancing its taste and improving the digestibility of its milk. There is evidence that fermented milk products have been produced since around 10,000 BC. A range of different Lactobacilli strains has been grown in laboratories allowing for many cultured milk products with different flavors and characteristics.
Nasutitermes is a genus of termites. It consists of the following species:
Kefir or kephir, is a fermented milk drink similar to a thin yogurt that is made from kefir grains, a specific type of mesophilic symbiotic culture. The drink originated in the North Caucasus, Eastern Europe and Russia, where it is prepared by inoculating cow, goat, or sheep milk with kefir grains.
Cedecea is a genus of extremely rare bacteria of the family Enterobacteriaceae. The name of this genus was derived from CDC, the abbreviation for the Centers for Disease Control where the initial members of this genus were discovered. This genus resembles no other group of Enterobacteriaceae. Cedecea bacteria are Gram-negative, bacillus in shape, motile, nonencapsulated, and non-spore-forming. The strains of Cedecea appear to be similar to those of Serratia. Both Cedecea and Serratia are lipase positive and resistant to colistin and cephalothin; however, Cedecea is unable to hydrolyze gelatin or DNA.
This bacterial growth medium was developed in 1971 for Lactococcus species isolated from milk products. It was originally called M16 medium, but in 1975 Terzaghi and Sandine added disodium-β-glycerophosphate to the medium as a buffer, and named the new growth medium M17 medium. It was later found that the addition of disodium-β-glycerophosphate inhibits the growth of many Lactobacillus species.
Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls. The system, created by Rebecca Lancefield, was historically used to organize the various members of the family Streptococcaceae, which includes the genera Lactococcus and Streptococcus, but now is largely superfluous due to explosive growth in the number of streptococcal species identified since the 1970s. However, it has retained some clinical usefulness even after the taxonomic changes, and as of 2018, Lancefield designations are still often used to communicate medical microbiological test results in the United States.
Lactococcus piscium is a known fish pathogen affecting salmonid fish, which has nevertheless been found in other sources, such as packaged beef. Its type strain is NCFB 2778. L. piscium has shown promise as a bioprotective culture in the preservation of seafood. The bacterium has exhibited the ability to prevent sensory deterioration of food and inhibit the growth of other psychrophilic bacteria that may produce spoilage.
Chryseobacterium haifense is a psychrotolerant bacteria from the genus of Chryseobacterium which has been isolated from raw milk in Israel.
Sphingobacterium alimentarium is a Gram-negative and rod-shaped bacterium from the genus of Sphingobacterium which has been isolated from a dairy environment in Germany.
Sphingobacterium lactis is a Gram-negative and rod-shaped bacterium from the genus of Sphingobacterium which has been isolated from raw milk in Bavaria in Germany.
Naumannella halotolerans is a Gram-positive and aerobic bacterium from the genus of Naumannella which has been isolated from a pharmaceutical clean room and milk products in Sachsen-Anhalt in Germany.
Camelimonas is a genus of bacteria from the family of Beijerinckiaceae.
Lactococcus hircilactis is a Gram-positive and non-spore-forming bacterium from the genus of Lactococcus which has been isolated from raw goat milk in Valtellina in Italy.
Lactococcus nasutitermitis is a bacterium from the genus of Lactococcus which has been isolated from the gut of the termite Nasutitermes hainanensis.
Lactococcus fujiensis is a Gram-positive and facultatively anaerobic bacterium from the genus of Lactococcus which has been isolated from the leaves of Chinese cabbage from Fujinomiya in Japan.
Stenotrophomonas indicatrix is a Gram-negative, rod-shaped and none-spore-forming bacterium from the genus of Stenotrophomonas which has been isolated from the surface of a milking machine in Germany.
Sporosarcina newyorkensis is a Gram-positive and endospore-forming bacterium from the genus of Sporosarcina which has been isolated from human blood and raw cow milk.
References
- 1 2 Parte, A.C. "Lactococcus". LPSN .
- 1 2 "Lactococcus laudensis". www.uniprot.org.
- ↑ "Details: DSM-28961". www.dsmz.de.
- ↑ Meucci, A; Zago, M; Rossetti, L; Fornasari, ME; Bonvini, B; Tidona, F; Povolo, M; Contarini, G; Carminati, D; Giraffa, G (July 2015). "Lactococcus hircilactis sp. nov. and Lactococcus laudensis sp. nov., isolated from milk". International Journal of Systematic and Evolutionary Microbiology. 65 (7): 2091–6. doi: 10.1099/ijs.0.000225 . PMID 25833154.
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