Lactococcus Lactis

Taxonomic Classification:

Domain: Bacteria

Kingdom: Eubacteria

Phylum: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Streptococcaceae                                                   

Genus: Lactococcus

Species: L. lactis [12]


Figure 1: Lactococcus lactis, Gram stained smear; 100x              

Why does this organism belong in this Domain?

             Lactococcus lactis is a prokaryote bacteria that is unicellular and reproduces by binary fission. [16] These are some of the main characteristics of an organism in the Domain Bacteria. The organism has to be prokaryote, unicellular, and reproduce asexually like binary fission. [3] However these characteristics fit for both Domain Archaea and Bacteria, but one of the few differences between them that makes a big contrast is that Bacteria has peptidoglycan in its cell wall which is one thing Archaea is lacking. [17] In the cell wall of Lactococcus lactis, there is the presence of peptidoglycan. This component is the major component of a gram-positive bacteria such as, Lactococcus lactis. [18] They both have the same metabolic pathway, using fermentative metabolism. This organism is one of the many organisms in the lactic acid bacteria category. [12] [3] This bacteria’s fermentation is based on metabolic stability,  their resistance to the bacteriophage, and have the ability to produce compounds usually from the use of amino acids catabolism. [15] This being said, bacteria has broad topics for metabolism, containing phototrophs, lithotrophs, and organotrophs. Also, most bacteria are able to grow in a laboratory. [3] Furthermore, this organism started by being isolated  from some green plants and grown in a laboratory like a most bacteria can. One of the many places this bacteria can be found is on plants and is able to be eaten by animals. Its main function is in the food fermentation of mostly milk products and  is beneficial to the kingdom of animals. [15] The domain bacteria is most lived in symbiotic and parasitic relationships with plants and animals just like this specific organism. [3] In addition, the main location of Lactococcus lactis is in dairy products where it can perform its main function. It is not an extreme location where the organisms from the Domain Archaea would be found. [17]

General Description:

          The Lactococcus lactis is about the average length of 0.5- 1.5µm. The shape of this organism is usually found in a sphere shape found in pairs or in short chains. It is usually found with plant material and grasses, which both can be found in milk.  Their main location is found in milk and in food fermentations. [14] This organism is used for fragmentation because of its metabolic stability, with their counter affect to bacteriophage, and ability of producing amino acids in catabolism. Lactococcus Lactis is easily adaptive to its environment. When it has to adapt to environment, it quickly changes its metabolism based on their amount of carbohydrates. These elements result in gene duplication, translocation, inversion, deletion and horizontal transfer events. [15] It has become its own genus and species based on the pH, salt, and temperature tolerance for growth. Its main function is to take the ferments of milk sugar and then make it into lactic acid. When it is added to milk, the organism uses enzymes to produce ATP from the lactose. When ATP is produced, lactic acid separates and this will make curds. This organism lowers the pH of a milk product and therefore preserves it for a longer time.   

            This organism is vital to the production of cheese and whey. But also this specific organism is Gram-positive, non- motile, and is incapable of forming spores. It is part of a family of lactic acid bacteria. Other organisms similar to this one can be Lactobacillus acidophilus, and Streptococcus saliuarius. Lactococcus lactis is a beneficial bacteria that has helped the milk and cheese industry strive. [14]

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