Phage t: a group T plasmid-dependent bacteriophage.

Area of Science:

• Microbiology
• Virology
• Bacteriology

Background:

• Bacteriophages (phages) are viruses that infect bacteria.
• Plasmids are extrachromosomal DNA elements that can confer various traits to bacteria, including antibiotic resistance.
• Incompatibility group T plasmids are a specific class of bacterial plasmids.

Purpose of the Study:

• To isolate and characterize a novel bacteriophage from sewage.
• To determine the host range and specific requirements for infection of the isolated phage.
• To investigate the phage's interaction with bacterial plasmids, particularly those of incompatibility group T.

Main Methods:

• Isolation of bacteriophage from sewage samples.
• Plaque assays on various bacterial strains, including Escherichia coli and Salmonella typhimurium, with and without specific plasmids.
• Determination of phage growth and lysis in different host strains.
• Plasmid transfer experiments (conjugation) to assess phage sensitivity acquisition.
• Electron microscopy for phage morphology and adsorption studies.

Main Results:

• A bacteriophage, designated Phage T, was isolated from Pretoria sewage.
• Phage T exclusively formed plaques on Escherichia coli and Salmonella typhimurium strains harboring incompatibility group T plasmids.
• Visible lysis was observed on R+ host strains carrying five out of six tested group T plasmids.
• While Rts1 plasmid-carrying strains supported phage growth, they did not show visible lysis.
• Phage adsorption was observed on the pili determined by T plasmids.

Conclusions:

• Phage T exhibits specific host tropism, dependent on the presence of T-incompatibility group plasmids.
• The phage's interaction with plasmids, including adsorption to pili, highlights a unique phage-host-plasmid relationship.
• This phage serves as a valuable tool for studying T plasmid biology and phage-bacteria interactions.