In order to determine if plcD and/o

In order to determine if plcD and/or plcI code immunity proteins for PlcA, the genes were cloned individually or together in the NisA-inducible vector pNZ8048 and transformed into L. lactis NZ9000. The recombinant strain L. lactis NZ9000 – pNZPlcDI induced with nisin A displayed full resistance to PlcA while strains L. lactis NZ9000 – pNZPlcD and L. lactis NZ9000 – pNZPlcI induced with nisA showed 86 % and 62 % sensitivity against PlcA, respectively, in comparison to the activity of the bacteriocin against the control strain L. lactis NZ9000 – pNZ8048 (Figure 3b). Therefore, although both proteins individually appeared to confer partial immunity to L. lactis NZ9000 against the antimicrobial activity of PlcA, the recombinant strain was fully protected against the action of PlcA when both proteins were being produced concomitantly. Similar results have been observed with other circular bacteriocins such as carnocyclin A, where the production of the immunity protein (CclI) was not enough to confer full protection to the producer and only when CclD and CclI were co- produced did the strain show full immunity (35).