HOST-CONTROLLED MODIFICATION AND RESTRICTION IN BACILLUS-SUBTILIS BSU168-SYSTEM AND BSUR-SYSTEM IN B-SUBTILIS 168

A Bsu168-specific restriction deficient (r168-) mutant of Bacillus subtilis Marburg 168 was transformed to be BsuR-specific restriction proficient (rR+) with B. subtilis R DNA as efficiently as the Bsu168-specific restriction proficient (r168+) parental strain (hsrM+, hsdR-). We constructed rR+mR+r168+m168+strain (ISMR 4), rR+mR+r168-m168+strain (ISR 11) and rR+mR+r168-m168-strain (ISR 6) from strain 101 (r168+m168+), strain 1012 (r168-m168+) and strain RM125 (r168-m168-), respectively by transformation with B. subtilis R DNA, and tested their restriction and modification activities on phage φ{symbol}105C. The results show that the sites recognized by Bsu168-specific restriction and modification enzymes and the sites recognized by BsuR-specific ones are not overlapping. We conclude that the Bsu168-modification and restriction system and the BsuR-modification and restriction system are controlled independently by two distinct sets of genes in the rR+mR+transformant of r168+m168+strain B. subtilis 168. © 1979 Springer-Verlag.