the determinants for nisin production and immunity to two components of a starter culture for Gouda cheese manufacture. Both production and immunity were transferred to the citrate-utilising component, L.lactis subsp. lactis (biovar. diacetylactis) and immunity only to L. lactis subsp. cremoris. Cheese made with these starters showed increased protection against the development of C. tyrobutyricum and Staphylococcus aureus throughout ripening