Genes affecting coliphage BF23 and E colicin sensitivity in Salmonella typhimurium

Area of Science:

• Microbiology
• Bacteriology
• Molecular Biology

Background:

• Salmonella typhimurium exhibits sensitivity to coliphage BF23.
• Coliphage resistance (bfe) mutants were isolated in S. typhimurium.
• Previous studies indicated potential interactions between phages and colicins.

Purpose of the Study:

• To investigate the genetic basis of coliphage BF23 resistance in Salmonella typhimurium.
• To determine the role of the bfe+ protein in phage and colicin interactions.
• To elucidate the mechanism of E colicin activity in S. typhimurium.

Main Methods:

• Isolation and characterization of spontaneous BF23-resistant mutants (bfe) in S. typhimurium.
• Genetic mapping of the bfe gene using phage P1 transduction.
• Colicin adsorption assays measuring the loss of killing units and direct binding of labeled colicin E2.
• Complementation studies using an F'8 gal+ episome from Escherichia coli.

Main Results:

• The bfe gene was mapped between argF and rif loci in S. typhimurium.
• S. typhimurium strains with bfe+ adsorbed both phage BF23 and E colicins (E2, E3).
• Sensitivity to colicins E1, E2, and E3 was restored in a strain carrying an F'8 gal+ episome, which complemented E. coli tolB mutations.
• Efficient E colicin killing in S. typhimurium appears to require expression of an E. coli gene, possibly tolB.

Conclusions:

• The bfe+ protein is crucial for the adsorption of both coliphage BF23 and E colicins in S. typhimurium.
• Efficient killing by E colicins in S. typhimurium necessitates the expression of a gene, potentially tolB, from E. coli.
• This study reveals a shared mechanism for phage and colicin adsorption mediated by the bfe+ protein.