Phages I alpha and I2-2: IncI plasmid-dependent bacteriophages

Area of Science:

• Microbiology
• Virology
• Bacteriology

Background:

• Bacteriophages (phages) are viruses that infect bacteria and can be specific to certain bacterial strains or plasmids.
• Understanding phage-host interactions is crucial for potential applications in biotechnology and medicine.

Purpose of the Study:

• To isolate and characterize novel bacteriophages from environmental sources.
• To determine the host range, morphology, and adsorption properties of the isolated phages.

Main Methods:

• Isolation of phages from sewage samples.
• Plaque assays to determine host range and efficiency of plating.
• Electron microscopy for phage morphology.
• Resistance assays to chloroform and RNAase.

Main Results:

• Phage I alpha, an RNA phage with hexagonal symmetry, was isolated from Windhoek sewage and infects Escherichia coli and Salmonella typhimurium strains carrying I1 plasmids, adsorbing to I1 pili.
• Phage I2-2, a filamentous DNA phage sensitive to chloroform, was isolated from Pretoria sewage and infects strains with I2 plasmids, though its adsorption site was not identified.
• Both phages exhibited distinct plaque morphologies and host specificities.

Conclusions:

• The characterization of phages I alpha and I2-2 expands the knowledge of phage diversity and their specific interactions with bacterial plasmids.
• These findings contribute to the understanding of phage biology and could inform future phage-based applications.