Development of a soft cheese with integrated Listeria monocytogenes biosensor

Listeria monocytogenes is a gram-positive, rod-shaped, food-borne bacterium, capable of causing the rare but potentially fatal disease listeriosis. L.monocytogenes can replicate at temperatures as low as 0°C allowing it to survive in industrial and domestic refrigerators. L.monocytogenes can often grow in soft cheeses, making many varieties of cheese unavailable to those who are immunosuppressed. Man-Cheester aims to modify Lactococcus lactis, a common bacterium in cheese manufacture. We will transform L. lactis in a cheese starter culture to detect AIP, a key quorum signalling molecule produced by L. monocytogenes. This will be done by expressing the agr quorum-sensing system used by L.monocytogenes in L. lactis. On detection of AIP, a colour change will occur within L. lactis causing the cheese to turn purple, alerting the consumer to its contamination. Our concept could be further developed to include other sources of L. monocytogenes contamination such as meats and vegetables to prevent as many cases of listeriosis as possible.