Construction of A Replicon-deficient Plasmid of Two-component Food-grade Selectable Marker for Lactococcus lactis
XU Bo, CAO Yu-Sheng, ZHOU Yan-Qin
1.College of Biology Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China;2.Key Laboratory of Food Science, Ministry of Education, Jiangxi-OAI Joint Research Institute, Nanchang University, Nanchang 330047, China
The two-component food-grade selectable marker for Lactococcus. lactis NICE system (the nisin-controlled expression system) has the advantages of dominant and complementation markers. One component is a replicon-deficificient companion plasmid, which carries an erythromycin resistance gene (Emr) as a selectable marker and it’s replication is depended on the other food-grade cloning vector which carries the functional replicon, is entirely made up of L.lactis DNA and has no selection marker. The pMG36e and pRAF800 are the sources of Emr and rep for the pEmr:rep. The rep B-deficient companion plasmid can be constructed by enzyme digestion, deficiency and ligation and coexisting with the theta replicon only.