<p6><i>Listeria monocytogenes </i> 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. <i>L.monocytogenes</i> can often grow in soft cheeses, making many varieties of cheese unavailable to those who are immunosuppressed. Man-Cheester aims to modify <i>Lactococcus lactis</i>, a common bacterium in cheese manufacture. We will transform <i>L. lactis</i> in a cheese starter culture to detect AIP, a key quorum signalling molecule produced by <i>L. monocytogenes</i>. This will be done by expressing the agr quorum-sensing system used by <i>L.monocytogenes</i> in <i>L. lactis</i>. 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 <i>L. monocytogenes</i>  contamination such as meats and vegetables to prevent as many cases of listeriosis as possible.</p6>