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Basic characterization of a lipid-containing bacteriophage specific for plasmids of the P, N, and W compatibility
Abstract:
Preliminary studies have shown that bacteriophages PR3 and PR4, originally isolated on Pseudomonas aeruginosa, resemble the lipid-containing phage PM2 in appearance. Their host range extends intergenerically to species carrying drug-resistance plasmids of the P and N compatibility groups. In this paper, the serological identity of the two isolates is established and it is concluded that they are the same virus, but with some differences in growth characteristics. They contain double-stranded DNA and are probably icosahedra (65 nm) with short (47 nm) noncontractile tails. Their sensitivity to chloroform and low buoyant density in CsCl(1.265 g/ml) indicate that they contain lipid which is probably located in the thickened inner layer of the capsid. A study is made of their adsorption efficiencies to sensitive and resistant bacteria, and it is found that, unlike most sex-specific phages, they adsorb directly to the cell surface and not to sex pili. Their host range is shown to include strains harboring a drug-resistance plasmid of the W compatibility group.
Insights
Two Pseudomonas aeruginosa phages, PR3 and PR4, are identified as the same lipid-containing virus. These phages adsorb directly to bacterial cell surfaces, not sex pili, and infect strains with specific drug-resistance plasmids.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Bacteriophages PR3 and PR4, isolated from Pseudomonas aeruginosa, share morphological similarities with the lipid-containing phage PM2.
- Their known host range includes species with drug-resistance plasmids from P and N compatibility groups.
Purpose of the Study:
- To establish the serological identity of bacteriophages PR3 and PR4.
- To characterize their physical, chemical, and biological properties, including adsorption mechanisms and host range.
- To compare their characteristics with known lipid-containing phages like PM2.
Main Methods:
- Serological testing to confirm viral identity.
- Electron microscopy for morphological analysis (icosahedral shape, tail structure).
- Buoyant density centrifugation in CsCl to determine lipid content.
- Adsorption assays on sensitive and resistant bacterial strains.
- Host range determination across various bacterial strains harboring different drug-resistance plasmids.
Main Results:
- Bacteriophages PR3 and PR4 are serologically identical, representing the same virus with slight growth variations.
- They possess double-stranded DNA, are likely icosahedral (65 nm) with short tails (47 nm), and contain lipids, indicated by chloroform sensitivity and low buoyant density (1.265 g/ml).
- These phages adsorb directly to the bacterial cell surface, independent of sex pili, and their host range includes strains with W compatibility group drug-resistance plasmids.
Conclusions:
- Bacteriophages PR3 and PR4 are confirmed as the same lipid-containing virus, distinct from typical sex-specific phages due to their direct adsorption mechanism.
- Their lipid content and unique adsorption strategy offer insights into phage-host interactions and potential applications in combating antibiotic-resistant bacteria.