An Engineered R-Type Pyocin Is a Highly Specific and Sensitive Bactericidal Agent for the Food-Borne Pathogen Escherichia coli O157:H7

Abstract

Some strains of Pseudomonas aeruginosa produce R-type pyocins, which are high-molecular-weight phage tail-like protein complexes that have bactericidal activity against other Pseudomonas strains. These particles recognize and bind to bacterial surface structures via tail fibers, their primary spectrum determinant. R-type pyocins kill the cell by contracting a sheath-like structure and inserting their hollow core through the cell envelope, resulting in dissipation of the cellular membrane potential. We have retargeted an R-type pyocin to Escherichia coli O157:H7 by fusing a tail spike protein from an O157-specific phage, V10, to the pyocin tail fiber. The V10 tail spike protein recognizes and degrades the O157 lipopolysaccharide. This engineered pyocin, termed AVR2-V10, is sensitive and specific, killing 100% of diverse E. coli O157:H7 isolates but no other serotypes tested. AVR2-V10 can kill E. coli O157:H7 on beef surfaces, making it a candidate agent for the elimination of this pathogen from food products. All rare AVR2-V10-resistant mutants isolated and examined have lost the ability to produce the O157 antigen and are expected to have compromised virulence. In addition, E. coli O157:H7 exposed to and killed by AVR2-V10 do not release Shiga toxin, as is often the case with many antibiotics, suggesting potential therapeutic applications. The demonstration that a novel R-type pyocin can be created in the laboratory by fusing a catalytic tail spike from the family Podoviridae to a tail fiber of a member of the family Myoviridae is evidence that the plasticity observed among bacteriophage tail genes can, with modern molecular techniques, be exploited to produce nonnatural, targeted antimicrobial agents.

The xnp1 P2-Like Tail Synthesis Gene Cluster Encodes Xenorhabdicin and Is Required for Interspecies Competition

“…Similarly, the pts cluster required for the production of photorhabdicin in P. luminescens contains multiple fiber genes in the same location (10). Variation at the C terminus of fiber proteins created by DNA inversion or recombination, or replacement of the native fiber gene with one from a related strain, alters the spectrum of activity of the respective R-type bacteriocins (24,27,40). Recombination between the C-terminal domain of xnpH1 and tail fiber genes adjacent to xnpH1 in a subpopulation of cells could expand the range of xenorhabdicin activity and enhance the ability of X. nematophila to compete against other Xenorhabdus and Photorhabdus strains and possibility less related bacteria.…”

“…They are composed of an outer sheath, an inner tube, and associated tail fibers. R-type pyocins bind via tail fibers to lipopolysaccharide (LPS) receptors on the surface of sensitive bacteria (18,24,27,40). It has been shown that recombination of tail fiber proteins broadens R-type bacteriocin specificity (24).…”

Bacteriocin-mediated competition in cystic fibrosis lung infections

“…The soluble S-type is similar to colicins of E. coli and is composed of killing and immunity genes. While the R and F type are phage-derived and have different killing and resistance mechanisms, where both consist of only a killing component with no specified immunity that neutralizes the toxin but instead resist via alteration or absence of cell-surface receptors [2,[9][10][11][12][13][14][15].…”

Mycoviruses: future therapeutic agents of invasive fungal infections in humans?

“…The generated chimeric tail fibers that formed active pyocins resulted from many trials of empirically chosen fusion sites between prf15 and portions of bacteriophage tail/spike fibers. The engineered fusions between N-terminal portions of the pyocin tail fiber and various C-terminal portions of the bacteriophage tail/spike fibers resulted in pyocin host range expansion from Pseudomonas to Yersinia and various E. coli strains [70,71]. Scholl et al further envisage that an unlimited amount of chimeric pyocins can be created based on the presence of a vast number and diversity of bacteriophage tail fibres combined with the application of phage display techniques.…”