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The morphology of staphylococcal bacteriophage K and DNA metabolism in infected Staphylococcus aureus
Abstract:
The morphology and dimensions of bacteriophage K particles were determined by electron microscopy. This virus had an icosahedral head (approx. 70 nm diam.) and a long (210 nm) thin (15 nm) contractile tail which terminated in a complex basal appendage. The precise dimensions of the particles were dependent on the negative stain employed. The buoyant densities of the K virus particle and its DNA were 1 X 479 g/ml and 1 X 689 g/ml respectively. The DNA had a base composition of 30% G + C, a contour length of 16 X 1 micron and a calculated mol. wt. of 33 X 10(6). With Staphylococcus aureus (NCTC 9318) as host, the latent period was 25 min, the eclipse period 14 min and the average burst size 60 p.f.u./bacterium. Infection resulted in inhibition of host DNA synthesis and degradation of the bacterial DNA: the products were used for tee synthesis of phage DNA. The kinetics of DNA synthesis is infected and uninfected bacteria were examined. There was no initial cessation of DNA synthesis in the infected bacteria.
Insights
Bacteriophage K, a virus infecting Staphylococcus aureus, has a distinct structure and replicates by hijacking bacterial DNA synthesis. Its infection cycle inhibits host DNA production, redirecting resources for phage DNA creation.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Bacteriophages are viruses that infect bacteria.
- Understanding bacteriophage structure and replication is crucial for microbiology and biotechnology.
- Staphylococcus aureus is a significant human pathogen.
Purpose of the Study:
- To characterize the morphology and dimensions of bacteriophage K.
- To investigate the replication cycle and DNA metabolism during bacteriophage K infection of Staphylococcus aureus.
- To determine the physical and biochemical properties of bacteriophage K and its DNA.
Main Methods:
- Electron microscopy for morphological analysis.
- Buoyant density centrifugation for particle and DNA density determination.
- DNA extraction and analysis for base composition and contour length.
- One-step growth curve analysis to determine latent and eclipse periods and burst size.
- Measurement of host and phage DNA synthesis kinetics.
Main Results:
- Bacteriophage K possesses an icosahedral head (70 nm) and a contractile tail (210 nm x 15 nm) with a basal appendage.
- The phage DNA has a G+C content of 30%, a contour length of 16.1 µm, and a molecular weight of 33 x 10^6.
- Infection of Staphylococcus aureus resulted in a latent period of 25 min, eclipse period of 14 min, and burst size of 60 p.f.u./bacterium.
- Phage infection inhibited host DNA synthesis and degraded bacterial DNA, with products utilized for phage DNA synthesis.
- No initial cessation of DNA synthesis was observed in infected bacteria.
Conclusions:
- Bacteriophage K exhibits unique morphological characteristics and a defined replication strategy.
- The phage actively manipulates host DNA metabolism for its own replication.
- These findings contribute to the understanding of bacteriophage-host interactions and DNA replication mechanisms.