Bacillus subtilis mutation blocking irreversible binding of bacteriophage SPP1

Area of Science:

• Microbiology
• Virology
• Bacteriophage Research

Background:

• Bacteriophages are viruses that infect bacteria, playing crucial roles in microbial ecosystems.
• Understanding phage-host interactions is vital for applications in biotechnology and medicine.
• Bacillus subtilis is a model organism for genetic and molecular studies.

Purpose of the Study:

• To isolate and characterize Bacillus subtilis mutants resistant to bacteriophage SPP1 infection.
• To investigate the mechanism of phage resistance at the adsorption and infection stages.
• To map the genetic locus responsible for the observed phage resistance.

Main Methods:

• Isolation of Bacillus subtilis 168 mutants resistant to bacteriophage SPP1.
• Adsorption assays to confirm phage binding to mutant cells.
• Infection assays to determine the success of phage replication.
• Phage recovery experiments to assess infectivity post-adsorption.
• Genetic mapping using PBS1 transduction and cotransduction analysis with ald-1.

Main Results:

• Mutants were isolated that permitted SPP1 phage adsorption but inhibited subsequent infection.
• Recovered phages from these mutants retained their infectivity.
• The resistance phenotype was specific to SPP1 and related phages (41c, 22a, p15, SF6).
• The mutation, designated pha-2, was mapped with high cotransduction frequency (95%) to the ald-1 locus.

Conclusions:

• The pha-2 mutation confers resistance to SPP1 infection in Bacillus subtilis by blocking a post-adsorption step.
• This resistance mechanism is specific and does not affect phage adsorption.
• The genetic mapping provides a basis for further molecular characterization of the resistance mechanism.