Figure 1.

Temperate phages’ contributions to host bacterial pathogenicity. There are three major ways that temperate phages increase the pathogenicity of their host. (a) Firstly, temperate phages can transfer the virulence genes encoding for toxins and adhesion proteins to their hosts (leftmost panel). (b) Secondly, temperate phages can transfer ARGs originally located within the phage genome or from exogenous sources (host chromosome and plasmids), contributing to the emergence of antibiotic-resistant strains (middle panel). The mechanisms of phage-mediated transfer of ARGs are further demonstrated in detail (bottom panel): (b1) The temperate phage can carry ARGs and then introduce the genes to a new bacterial host genome after phage integration. (b2) During the induction of a temperate phage, the host cell lyses and releases an intact ARG-containing plasmid, which can enter a new bacterial cell through transformation. (b3) In some cases, an ARG-containing plasmid can mistakenly be packaged in a phage capsid and subsequently transferred to a new bacterial cell by phage transduction. (b4) The temperate phage can collect ARGs from the bacterial chromosome by generalized or specialized transduction. (c) Finally, gene transfer by temperate phages can promote bacterial biofilm formation through either their integration into or excision out of the host genome, increasing the host’s resistance to antimicrobial treatments (rightmost panel). Abbreviations: OMVs, outer membrane vesicles; ARG, antibiotic resistance genes.