Team:Groningen/Template/MODULE/home/overview/overview2

Lactococcus lactis is well-known in basic microbiology, genetics, molecular biology, as well as in food science and biotechnology. Lactococcus lactis, is currently very important for industrial fermentations, especially dairy products. In 1909 this bacterium became also known as Streptococcus lactis. And only until recently it was renamed and clearly separated from the genera of streptococci again¹.

L. lactis is generally known to be safe for human consumption², and they have never been identified as a cause for infectious disease. Because of this fact, this bacterium is used in large quantities in the dairy industries in the production of many different products like cheese and buttermilk.

L. lactis is a gram-positive bacterium with non-motile, round-shaped cells which does not form spores. Depending on their growth conditions they typically appear to be 0.5-1.5µm in size. A characteristic of the L. lactis that makes them different then members of the Streptococcus genus, is that these species grow in pairs or in short chains, unlike the long chains that the Streptococcus species form.

Lactococci are found associated with plant material, mainly grasses, from which they are easily inoculated into milk. In order to be able to grown inside dairy products L. lactis relies on the degradation of dairy proteins into peptides. This bacterium uses enzymes to degrade the proteins to produce energy molecules (ATP) from lactose (or other dairy proteins). The byproduct of this process, lactic acid, is very important in fermentation and cheese productions. Also the lactic acid produced by the bacterium lowers the pH of the product and preserves it from the growth of unwanted bacteria and molds².

Furthermore L. lactis is capable of producing nisin, an antibiotic-like substance, called a bacteriocin. It is a natural antimicrobial agent with activity against a wide variety of Gram-positive bacteria, including food-borne pathogens such as Listeria, Staphylococcus and Clostridium by targeting the cell membrane. Nisin is a natural preservative present in cheese and it is also used as a preservative in heat processes and low pH foods³.

L. lactis was chosen for multiple reasons. To begin with we want to use the bacteria inside the active layer in the bandage, for this reason it is very important that the bacteria does not form spores since those can not be killed and escape our bandage. The second beneficial feature is that some strains in nature already produce nisin, a bacteriocin that can kill gram-positive bacteria. Thirdly it is considered a safe microorganism, and already widely used in food products. This increases the social acceptance of the use of a bacteria to fight other bacteria.

Also there is a group at molecular genetics within our university working with L. lactis, therefore it was possible to seek advice when needed.

At last we doubted about the use of L. lactis in our bandage because of the lactic acid production but after doing some research we even found some benefits in this. For example lactic acid is used to preserve food, which means it has an antimicrobial effect as mentioned before. This might help us fight the pathogens. To support this theory we found that wounds tolerate certain lactic acid concentrations without disturbing the wound healing⁴. Furthermore we found that lactic acid bacteria can even stimulate wound healing by up regulating certain neuropeptides⁵. Shortly said it seemed like the perfect bacteria/chassis for our bandage.