Two Restriction and Modification Systems in Staphylococcus aureus NCTC8325

Abstract
The presence of 2 distinct host specificities in S. aureus strain NCTC8325 was revealed by the isolation of [DNA] restriction- and modification-deficient mutants. The 2 host specificity systems, designated S1 and S2, are active on phage 80.mu..alpha. but are not additive in their restricting activity. Restriction-deficient, modification-proficient mutants were invariably affected in both restriction systems. The functional relationship between these 2 systems is discussed.