A mutant bacteriophage evolved to infect resistant bacteria gained a broader host range

Area of Science:

• Microbiology
• Virology
• Evolutionary Biology

Background:

• Bacteriophages (phages) are ubiquitous and play crucial roles in microbial ecosystems.
• Understanding phage host range expansion is vital for microbial ecology and phage therapy.
• The coevolution of Bacillus subtilis and phage SPO1 provides a model for studying host-phage interactions.

Purpose of the Study:

• To investigate the mechanisms by which bacteriophages acquire new hosts.
• To analyze the coevolutionary dynamics between Bacillus subtilis and phage SPO1.
• To understand how phage mutations enable the expansion of host range.

Main Methods:

• Co-cultivation of Bacillus subtilis and phage SPO1 to observe evolution.
• Isolation and characterization of phage-resistant bacterial mutants.
• Genomic analysis of evolved phages to identify mutations.
• Functional assays to determine phage-host binding and infection capabilities.

Main Results:

• Phage-resistant Bacillus subtilis mutants were defective in glycosylated wall teichoic acid (WTA) production.
• An evolved SPO1 phage mutant acquired the ability to infect resistant bacteria.
• Mutations in phage genes encoding baseplate and fibers were identified.
• The evolved phage demonstrated an expanded host range, infecting non-host Bacillus species by adhering to the conserved WTA backbone.

Conclusions:

• Phage evolution can lead to host range expansion by altering surface attachment proteins.
• Loss of dependency on specific glycosylation patterns facilitates crossing species barriers.
• The study provides insights into the molecular basis of phage adaptation and host jumping.