A Microbial Biorealm page on the genus Lactococcus lactis
Higher order taxa
Bacteria, Firmicutes, Bacilli, Lactobacillales, Streptococcacaeae, Lactococcus
Description and significance
Lactococcus lactis is a rod shaped, Gram-positive bacteria used widely for industrial production of fermented dairy products like milk, cheese, and yogurt. These are important food supply for many people, so extensive research has been done on the microorganism’s metabolic pathway to increase its efficiency for dairy production. Due to its important application, simple metabolism and limited biosynthetic capabilities, its genome is sequenced to help researchers understand genes that are responsible for its fermentation pathway. Furthermore, scientists study DNA recombination to improve its survival and resistance to antibiotics and to manipulate its metabolic pathways to be better used for industrial production. (10) Aside from its high use in industrial application, it can also be found in the wild on plants and some body parts of cows. It is believed that in nature, L. lactis stays dormant on plant surface awaiting to be ingested along with the plant into animal gastrointestinal tract, where it becomes active and multiplies intensely (1). Not only it is important in dairy production, it also has potential of use as oral vaccine, foreign protein production and metabolite through genetic engineering to manipulate L. lactis in researchers’ favor (2). Lactococcus lactis has two subspecies with few phenotype and genotype difference, Lactococcus lactis subsp. lactis and subsp. cremoris, where subsp lactis is preferred for making soft cheese while subsp. cremoris is for hard cheese (1). These organisms were originally classified under the genus Streptococcus, but in 1985, it was assigned to the current genus (3). Recently, one method of distinguishing between the two subspecies was announced. Observation of glutamate decarboxylase (GAD) can be found in the subspecie lactis, but not in subspecie cremoris. “GAD catalyzes the irreversible decarboxylation of glutamate to -aminobutyric acid” with the glutamate-GABA antiporter (GABA) (4). The gene that encodes GAD in L. lactis subsp. cremoris is inactivated by a frameshift mutation resulting in a nonfunctioning protein.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.
Edited by student of Rachel Larsen and Kit Pogliano