Team:Concordia/Lactococcus Lactis

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Lactococcus lactis

Lactococcus lactis is a spherically shaped non-motile gram-positive bacterium, commonly found on the surfaces of plants and animals (1). The bacteria are dormant as they inhabit a plant’s surface, and will remain inactive until ingested by an animal and transported to the creature’s intestinal tract. In the intestinal environment, L. lactis will multiply and colonize. L. lactis has important industrial applications as it is used in the fermentation of foods and is essential in the manufacturing of cheeses and other dairy products such as cultured butter and yoghurt. It is closely related to the lactic-acid bacterial species Streptococcus salivarus and Lactobacillus acidophilus, which reside respectively in the mouth and the intestinal tract of humans

Because of L. lactis’ prominent presence in foodstuff and its close relationship with other bacteria that reside in our bodies, the ingestion of L. lactis is not expected to cause any adverse effects and is therefore considered a GRAS (Generally Recognized As Safe) organism. We have thus envisioned using L. lactis as a genetically engineered probiotic to be safely introduced to a person’s microbiome to enhance their health and metabolism. (We will of course not perform such human trials during our iGEM project). We determined L. lactis to be a feasible choice as our chassis organism as methods for transforming the bacteria have been established and molecular techniques to manipulate and metabolically engineer it are well characterized (2).

Since we are planning on adding an extracellular scaffold to L. lactis, we will be working with a strain of L. lactis that has been engineered to be deficient in extracellular proteases, and whose signal peptides, that are responsible for the secretion of proteins into the extracellular space, have been described. This strain has the ability to secrete and display proteins ranging from 9.8 to 165 kDa on its surface (3).

References

1	Nomura, M., Kobayashi, M., Narita, T., Kimoto-Nira, H., & Okamoto, T. (2006). Phenotypic and molecular characterization of Lactococcus lactis from milk and plants. Journal of Applied Microbiology, 101(2), 396–405
2	Holo, H., & Nes, I. F. (1995). Transformation of Lactococcus by electroporation. Methods Mol Biol, 47, 195-199
3	Wieczorek, A. S. (2012). Engineering Lactococcus lactis for the scaffold protein-mediated surface display of recombinant enzymes(Doctoral dissertation, Concordia University)