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Abortive replication of choleraphage phi 149 in Vibrio cholerae biotype el tor
R Chowdhury1, S K Biswas, J Das
1Biophysics Division, Indian Institute of Chemical Biology, Calcutta.
Abstract:
Choleraphage phi 149 adsorbed irreversibly to Vibrio cholerae biotype el tor cells, and 50% of the injected phage DNA bound to the cell membrane. Although no infectious centers were produced at any time during infection, the host macromolecular syntheses were shut off and the host DNA underwent chloramphenicol-inhibitable degradation. Synthesis of monomeric phage DNA continued similar to that observed in the permissive host. However, the concatemeric DNA intermediates produced were unstable and could not be chased to mature phage DNA. Pulse-labeling of UV-irradiated infected cells at different times during infection allowed identification of phage-specific proteins made in this nonpermissive host. Although most of the early proteins were made, only some of the late proteins were transiently synthesized.
Insights
Choleraphage phi 149 irreversibly binds Vibrio cholerae, halting host synthesis and degrading DNA. Phage DNA synthesis occurs, but unstable intermediates prevent mature phage production in this nonpermissive host.
Area of Science:
- Bacteriology
- Virology
- Molecular Biology
Background:
- Bacteriophages are viruses that infect bacteria.
- Understanding phage-host interactions is crucial for controlling bacterial infections.
- Choleraphage phi 149 is a bacteriophage that infects Vibrio cholerae.
Purpose of the Study:
- To investigate the infection mechanism of Choleraphage phi 149 in Vibrio cholerae biotype el tor.
- To characterize the molecular events occurring during this nonpermissive infection.
- To identify phage-specific proteins synthesized in the nonpermissive host.
Main Methods:
- Irreversible adsorption assays.
- Phage DNA binding studies.
- Host macromolecular synthesis inhibition assays.
- Chloramphenicol inhibition studies.
- Pulse-labeling and UV irradiation of infected cells.
- Analysis of phage DNA intermediates and protein synthesis.
Main Results:
- Choleraphage phi 149 irreversibly adsorbed to Vibrio cholerae, with 50% of injected phage DNA binding to the cell membrane.
- No infectious centers were produced, host macromolecular syntheses were shut off, and host DNA degraded in a chloramphenicol-inhibitable manner.
- Monomeric phage DNA synthesis occurred, but concatemeric intermediates were unstable, preventing mature phage DNA formation.
- Early phage proteins were synthesized, but only some late proteins were transiently produced in UV-irradiated infected cells.
Conclusions:
- Choleraphage phi 149 establishes a nonpermissive infection in Vibrio cholerae biotype el tor.
- The phage effectively shuts down host synthesis and degrades host DNA.
- Phage DNA replication is initiated but blocked at the stage of mature DNA formation due to unstable intermediates.
- Differential synthesis of phage proteins suggests regulatory mechanisms controlling gene expression in nonpermissive infections.