ADDITIVE EFFECTS OF 2 DIFFERENT PLASMID-LINKED RESTRICTION AND MODIFICATION SYSTEMS IN LACTOCOCCUS

Two plasmids, pND801 and pND802, encoding different restriction and mo dification systems were isolated from Lactococcus lactis ssp. lactis L L42-1 and Lactococcus lactis ssp. cremoris LC14-1, respectively. pND80 2 contained one Sphl restriction enzyme site and the whole plasmid was cloned into the Sphl site of the streptococcal/E.coli shuttle vector pSAB generating the plasmid pND803. pND803 was stably maintained in L. lactis MG1363 harbouring pND801.The combination of the two R/M systems within L.lactis MG1363 resulted in an additive resistance towards bot h isometric phage and prolate phage.