Bacteriophages of Bacteroides

Area of Science:

• Microbiology
• Virology
• Bacteriology

Background:

• Bacteroides species are significant anaerobic bacteria in the human gut microbiome.
• Accurate identification of Bacteroides species is crucial for clinical and research purposes.
• Bacteriophages (phages) are viruses that infect bacteria and have potential applications in diagnostics.

Purpose of the Study:

• To isolate and characterize bacteriophages specific to various Bacteroides species.
• To evaluate the feasibility of using these bacteriophages for the identification of Bacteroides species, particularly Bacteroides fragilis.
• To investigate the phenomenon of phage-carrier state (pseudolysogeny) in Bacteroides-phage interactions.

Main Methods:

• Isolation of bacteriophages from sewage samples targeting nine species of Bacteroides.
• Morphological characterization of isolated phages.
• Testing phage susceptibility of over 200 bacterial strains, including 144 strains of Bacteroides fragilis.
• Conducting blind trials for species identification using B. fragilis-specific phages.
• Detailed study of the phage-carrier state using Bacteroides fragilis phage Bf-1.

Main Results:

• Sixty-eight bacteriophages were isolated, with four distinct morphological types, three previously undescribed.
• Attempts at transduction using these phages on Bacteroides fragilis were unsuccessful.
• A phage identification scheme correctly identified 78% of Bacteroides fragilis strains within 24 hours.
• A phage-carrier state (pseudolysogeny) was observed in most phage-host systems.
• Bacterial capsules were implicated in resistance to phage infection and perpetuation of the carrier state.

Conclusions:

• Bacteriophages can be effectively used to develop a diagnostic scheme for identifying Bacteroides species, achieving high accuracy for Bacteroides fragilis.
• The phage-carrier state is a common phenomenon in Bacteroides-phage interactions, potentially influenced by bacterial capsule presence.
• Bacterial capsules may contribute to the virulence of Bacteroides strains by conferring resistance to phage predation.