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Changes in macromolecular synthesis in Xanthomonas oryzae infected with bacteriophage XP-12
Abstract:
Phage XP-12, which has complete substitution of the cytosine residues in its DNA with 5-methylcytosine residues, was shown to inhibit incorporation of uracil into host DNA and RNA during the latent period. This apparent inhibition of host macromolecular synthesis was not accompanied by extensive degradation of the host chromosome. Phage DNA synthesis in infected cells occurred at a faster rate than host DNA synthesis in analogous uninfected cells. However, phage DNA synthesis could not be accurately monitored by incorporation of [methyl-3H]thymidine into DNA because, soon after infection, there was a marked inhibition of utilization of exogenous thymidine for DNA synthesis. Phage infection conferred upon a thymine auxotrophic host the ability to synthesize thymine nucleotides for phage DNA synthesis. It is suggested that a phage-induced thymidylate synthetase activity is partially responsible for the inhibition of thymidine incorporation.
Insights
Phage XP-12 inhibits uracil incorporation into host DNA and RNA, yet supports its own DNA synthesis by inducing thymine nucleotide production. This phage also impairs thymidine utilization in the host.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Bacteriophage XP-12 possesses DNA with 5-methylcytosine instead of cytosine.
- Phage infection impacts host macromolecular synthesis during its latent period.
Purpose of the Study:
- To investigate the effects of bacteriophage XP-12 infection on host DNA and RNA synthesis.
- To understand the mechanisms behind phage DNA replication and thymidine metabolism in infected hosts.
Main Methods:
- Monitoring uracil and thymidine incorporation into host and phage DNA/RNA.
- Assessing host chromosome integrity post-infection.
- Evaluating thymine nucleotide synthesis in auxotrophic hosts.
Main Results:
- Phage XP-12 inhibits uracil incorporation into host DNA and RNA without significant host chromosome degradation.
- Phage DNA synthesis is rapid but difficult to track with [methyl-3H]thymidine due to inhibited thymidine utilization.
- Infected thymine auxotrophic hosts gain the ability to synthesize thymine nucleotides for phage DNA.
Conclusions:
- Phage XP-12 actively manipulates host metabolism, inhibiting uracil incorporation and inducing thymine synthesis.
- A phage-induced thymidylate synthetase likely contributes to the observed inhibition of thymidine incorporation.