Deoxyribonucleic Acid Synthesis in Bacteriophage SPO1-Infected Bacillus subtilis I. Bacteriophage Deoxyribonucleic Acid Synthesis and Fate of Host Deoxyribonucleic Acid in Normal and Polymerase-Deficient Strains

The effect of bacteriophage SPO1 infection of Bacillus subtilis and a deoxyribonucleic acid (DNA) polymerase-deficient (pol⁻) mutant of this microorganism on the synthesis of DNA has been examined. Soon after infection, the incorporation of deoxyribonucleoside triphosphates into acid-insoluble material by cell lysates was greatly reduced. This inhibition of host DNA synthesis was not a result of host chromosome degradation nor did it appear to be due to the induction of thymidine triphosphate nucleotidohydrolase. Examination of the host chromosome for genetic linkage throughout the lytic cycle indicated that no extensive degradation occurred. After the inhibition of host DNA synthesis, a new polymerase activity arose which directed the synthesis of phage DNA. This new activity required deoxyribonucleoside triphosphates as substrates, Mg²⁺ ions, and a sulfhydryl reducing agent, and it was stimulated in the presence of adenosine triphosphate. The phage DNA polymerase, like that of its host, was associated with a fast-sedimenting cell membrane complex. The pol⁻ mutation had no effect on the synthesis of phage DNA or production of mature phage particles.