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Phage Phenomics: Physiological Approaches to Characterize Novel Viral Proteins
Published on: June 11, 2015
Characterization of group H streptococcal temperate bacteriophage phi 227
Journal of Virology
|March 1, 1977
Summary
This study characterizes phi 227, a temperate phage from Streptococcus sanguis. Optimized propagation yielded high titers, and biophysical analysis revealed its DNA and protein composition, offering novel insights into streptococcal phages.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Streptococcus sanguis harbors temperate phages, but detailed characterization of their biological and biophysical properties is limited.
- Understanding phage-host interactions is crucial for microbial genetics and potential therapeutic applications.
Purpose of the Study:
- To propagate and characterize phi 227, a temperate phage from group H Streptococcus.
- To determine optimal conditions for phage yield and purification.
- To elucidate phage adsorption, replication, and biophysical properties.
Main Methods:
- Vegetative propagation of phi 227 in Streptococcus sanguis strain Wicky 4-EryR.
- Optimization of phage yield using multiplicity of infection, incubation time, and diatomaceous earth treatment.
- Characterization of phage adsorption, infectious center formation, and single-step growth.
- Analysis of phage replication sensitivity to metabolic inhibitors.
- Biophysical characterization including buoyant density, protein composition, and DNA molecular weight and GC content.
Main Results:
- Optimized propagation achieved titers of 1-2 x 10(10) PFU/ml with efficient purification.
- Calcium was essential for infectious center formation, and the phage receptor on cell walls resisted trypsin and heat.
- Single-step growth revealed a latent period of 39 min and burst size of 100 PFU/infectious center, with temperature affecting these parameters.
- Phage replication was sensitive to host metabolic inhibitors, suggesting phi 227 does not encode a resistant RNA polymerase.
- Biophysical analysis identified phi 227 as a type B phage with a buoyant density of 1.50 g/cm³, five proteins, and duplex linear DNA (MW 23.2 x 10^6 Da, 42.3% GC content).
Conclusions:
- Phi 227 propagation and purification can be optimized for high yields.
- Calcium-dependent mechanisms are involved in phi 227 infection, and its receptor has specific properties.
- Phage replication relies on host metabolic pathways, and its genetic material is double-stranded DNA.
- This study provides the first comprehensive biophysical characterization of a streptococcal phage, establishing a foundation for future research.
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