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Phosphate repression of phage protein synthesis during infection by choleraphage phi 149
Abstract:
A synthetic medium for choleraphage phi 149 growth, in which the concentration of phosphate ions plays a significant role, has been defined. Upon infection, choleraphage phi 149 DNA binds to the cell membrane at three to four sites. The host macromolecular syntheses are shut off by 10 min after infection and the synthesis of phage-specific DNA is detectable after 20 min of infection. The phage utilizes primarily the host DNA degradation products for its own DNA synthesis. When added during the first 20 min of infection both nalidixic acid and novobiocin inhibit phage growth. The effects of these antibiotics are not pronounced when added late during infection. Pulse labeling of ultraviolet-irradiated infected cells at different times during infection has allowed identification of about 50 phage-specific proteins of which 19 are structural proteins. These proteins appear during the infection cycle in two distinct phases, early and late. When infection is carried out in high-phosphate medium, none of the late proteins is synthesized. Eleven of the 26 early proteins detected are DNA-binding proteins.
Insights
Choleraphage phi 149 DNA binds to host cell membranes, utilizing host DNA for replication. Phosphate levels and early antibiotic treatment significantly impact phage protein synthesis and growth.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Bacteriophages, viruses that infect bacteria, are crucial tools in molecular biology research.
- Understanding phage-host interactions is key to deciphering viral replication strategies.
- Choleraphage phi 149 offers a model system to study infection dynamics in Vibrio cholerae.
Purpose of the Study:
- To define a synthetic growth medium for choleraphage phi 149.
- To elucidate the molecular mechanisms and temporal events of choleraphage phi 149 infection.
- To identify phage-specific proteins and their roles during the infection cycle.
Main Methods:
- Defined a synthetic medium for choleraphage phi 149 cultivation, optimizing phosphate ion concentration.
- Utilized pulse labeling and UV irradiation of infected cells to identify phage-specific proteins.
- Administered antibiotics (nalidixic acid, novobiocin) at different infection stages to assess their impact on phage growth.
Main Results:
- Choleraphage phi 149 DNA binds to host membranes; host macromolecular synthesis ceases by 10 min post-infection.
- Phage DNA synthesis begins at 20 min, utilizing host DNA degradation products.
- Antibiotics inhibit phage growth when added early but not late in infection.
- Identified approximately 50 phage-specific proteins, including 19 structural proteins, appearing in early and late phases.
- High-phosphate medium prevents synthesis of late phage proteins; 11 early proteins are DNA-binding.
Conclusions:
- Phosphate concentration critically regulates choleraphage phi 149 infection, particularly late protein synthesis.
- The phage employs host DNA degradation products for its replication.
- Early-acting antibiotics interfere with essential phage replication steps.
- Characterized the temporal expression of phage proteins, distinguishing between early and late functions.