Two plasmids, pND801 and pND802, encoding different restriction and modification systems were isolated from Lactococcus lactis ssp. lactis LL42-1 and Lactococcus lactis ssp. cremoris LC14-1, respectively. pND802 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 both isometric phage and prolate phage.