Synthesis of DNA in phage-infected Bacillus subtilis

Bacteriophages of Bacillus subtilis.

“…Two phage-related enzymes involved in metabolizing thymine nucleotides, thymidine triphosphate nucleotidehydrolase (dTTPase; 257) and deoxythymidylate nucleotidehydrolase (d-TMPase; 8) are also synthesized shortly after infection, but it is not clear whether these enzymes play an essential role in phage production (72, 232). Since host DNA replication stops 6 to 8 min after phage addition (123,258), it was once thought that the two hydrolases might deplete the dTTP pool, thereby causing an inhibition in the synthesis of host DNA. However, it now appears that replication of the host genome is blocked by some other mechanism and the hydrolases may function to prevent incorporation of thymine into phage DNA.…”

“…When temperature-sensitive mutants of Oe having a heat-labile dTTPase infect thymine auxotrophs of B. subtilis at 45 C, exogeneous thymine is incorporated. However, host DNA replication is blocked and the thymine is actually polymerized into phage DNA (189,258). Although the phage DNA replication enzymes apparently cannot distinguish between thymine and HMU nucleotides, the native host enzymes can, as shown by the fact that HMU is not incorporated into the DNA of thymine-requiring auxotrophs ofB.…”

“…Two types of phage-directed proteins were thought to contribute to this depletion, an inhibitor of thymidylate synthetase (119), and hydrolases capable of degrading dTIP (257). This idea has been abandoned because suppression of host DNA replication occurs in cells infected with dTTPase-less phage mutants (258). A second hypothesis is that virus-related nucleases might degrade the host genome in a manner similar to that seen in coliphage infections.…”

Phage, Colicins, and Macroregulatory Phenomena

“…Host DNA synthesis stops a few minutes after infection with phage (pe. Roscoe (7) was able to show that the host DNA remains intact or, at least, that doublestrand breaks do not occur in detectable numbers. The enzymatic interference with the synthesis of thymidine triphosphate (dTTP) can be bypassed by using thymine-requiring host bacteria in the presence of thymine and by using phage mutants defective in dTTPase.…”

TRANSCRIPTION OF THE GENOME OF φ29. ANALYSIS OF mRNA SYNTHESIZED IN UV-IRRADIATED, INFECTED BACILLUS SUBTILIS

“…Also, the synthesis of all 029-specific RNA molecules requires a host RNA polymerase that is sensitive to rifampicin (9). Thus, in contrast to the large, virulent phages such as the T-even coli-phages (13,14) or B. subtilis phages ~z5e and SPOI (15,16) which strongly affect host-cell functions, 029 does not appreciably interfere with host-cell metabolism (6,9). For this reason, it is rather difficult to analyze ¢29 RNA transcripts in detail in infected cells unless host DNA transcription is repressed.…”