Heat Induction of Prophage Φ 105 in Bacillus subtilis: Bacteriophage-Induced Bidirectional Replication of the Bacterial Chromosome

摘要

A mutant of Bacillus subtilis, dna-1, which cannot initiate new rounds of DNA replication (obtained from N. Sueoka) was lysogenized with wild-type Φ 105 and with the heat-inducible mutant Φ 105 cts23. Bacteria were incubated at the permissive temperature in the presence of chloramphenicol and then shifted to the nonpermissive temperature where induction of Φ 105 cts23 occurs. DNA made after the shift was labeled with a density label, and the distribution of bacterial and phage markers in replicated and unreplicated DNA was determined. Similar experiments were performed with nonlysogenic dna-1 infected with phage Φ 105 cts23 after the temperature shift. The results show that after induction of Φ 105 cts23 prophage, bacterial markers on either side of the prophage replicate at an increased rate compared to more distant markers. No selective stimulation of bacterial DNA synthesis was observed on infection or after shifting bacteria lysogenic for noninducible phage to the higher temperature. Attempts to suppress the initiation mutation dna-1 by phage Φ 105 were unsuccessful.