Regulation of Chromosome Replication in Bacillus subtilis

Sequential replication of bacterial chromosomes has been suggested from the pattern of DNA synthesis after amino acid deprivation from amino acid requiring mutants of E. coli (Maaløe, 1961). More direct evidence has recently been reported in different systems. In the Bacillus subtilis transformation system, the replication of different markers in B. subtilis does not occur in random-in-time fashion but has a regular oriented pattern (Yoshikawa and Sueoka, 1962, 1963a, 1963b). Nagata (1962, 1963) reported evidence of sequential replication of the E. coli chromosome by studying the pattern of duplication of λ prophage in synchronized cultures of Hfr strains of E. coli K12. The unidirectional replication of E. coli chromosomes was also demonstrated from a radioautographic study by Cairns (1963).