Biophysical and microbiological aspects of the interaction between Yersinia pestis PsaA and bacteriophage L-413C

There has been a great interest in developing the phage-containing remedy against plague caused by antimicrobial resistant strains of Yersinia pestis, which have been increasingly isolated in recent years from sick humans and animals. Studies thus are under way to develop a "phage cocktail", which is expected to be effective against a wide range of pathogenic strains. Our paper sheds light on the role of Y. pestis antigen PsaA in reception of the phage L-413C, which might be a possible component of such a "cocktail". Using optical trapping (OT) and atomic force microscopy (AFM), we showed that PsaA-positive cells and PsaA-coated beads or cantilevers bound more effectively to a substrate coated with L-413C rather than Pokrovskaya phage. Comparing two isogenic strains of Y. pestis (EV and EV∆psaA), we found that when bacteria and phages are co-incubated under slightly acidic pH, as if in a eukaryotic cell, PsaA-positive cells bound the phage L-413C more effectively. There is good evidence to say that L-413C may become a component of a new anti-plague therapy due to its high ability to interact with the pili-forming protein PsaA from the outer membrane of Y. pestis.