Bacteriophage Infection Mediated by Molecules from Susceptible Organisms

A team of Israeli molecular microbiologists has found that bacteria that are resistant to infection by bacteriophages can lose this resistance when incubated together with susceptible bacteria.

The mechanism by which bacteria that are resistant to infection by phages become susceptible had not been well studied. To elucidate this mechanism, investigators at The Hebrew University of Jerusalem investigated phage dynamics in communities harboring phage-resistant (R) and sensitive (S) Bacillus subtilis bacteria.

Using cultures of B. subtilis and its lytic phage SPP1, they demonstrated that R cells, lacking SPP1 receptor, could be lysed by SPP1 when co-cultured with S cells. This unanticipated lysis was triggered in part by phage lytic enzymes released from nearby infected cells. They also discovered that occasionally phages could invade R cells, a phenomenon they termed acquisition of sensitivity (ASEN).

The investigators reported in the January 12, 2017, issue of the journal Cell that ASEN was mediated by R cells transiently gaining phage attachment molecules from neighboring S cells and that this molecular exchange was driven by membrane vesicles. They speculated that this exchange of phage attachment molecules could even occur in an interspecies fashion, enabling phage adsorption to non-host species, providing an unexplored route for horizontal gene transfer (HGT).

"In the present study, we show for the first time how bacteria entirely resistant to a given phage become susceptible upon co-incubation with sensitive bacteria. Phage invasion into resistant cells could have a major impact on transfer of antibiotic resistance and virulence genes among bacteria. This aspect should be carefully considered when employing phage therapy, as phage infection of a given species may result in gene transmission into neighboring bacteria resistant to the phage," said senior author Dr. Sigal Ben-Yehuda, professor of microbiology and molecular genetics at The Hebrew University of Jerusalem.