Bacteriophages direct several aspects of bacterial behavior and, considering the diversity and prevalence of the means described to date, we predict that the discovery of novel ways in which phages shape biological interaction networks will continue. As phages have been found that can impact carbon acquisition and metabolism, phages likely have roles in other key metabolic bacterial processes, such as nitrogen fixing. The ability of phages to alter bacterial survival in adverse conditions leads us to surmise that they may have roles in other specific behaviors such as chemotaxis and other adaptations in challenging environments, e.g. to heavy metal poisoning and exposure to irradiation.
Phages can modify bacterial behaviors either by directly introducing additional functions or by indirectly by regulating bacterial genes, e.g. by phage-encoded sigma factors. This paper presents several examples of how phages could increase cells defense, virulence, or survival in particular environments. The agr quorum sensing (QS) system is known to promote many of the behaviors and phenotypes discussed in this article, including toxin production, biofilm formation, motility, and sporulation. Alternatively, the phage QS genes may be a form of informing an expanded population of the same lysogen, (and therefore the phage), of its density within the environment with implications for induction and phage dynamics.
Bacteriophage behavioral ecology: How phages alter their bacterial host’s habits. Bacteriophage (2014) 4: e29866. doi: 10.4161/bact.29866
Bacteriophages have an essential gene kit that enables their invasion, replication, and production. In addition to this “core” genome, they can carry “accessory” genes that dramatically impact bacterial biology, and presumably boost their own success. The content of phage genomes continue to surprise us by revealing new ways that viruses impact bacterial biology. The genome of a Clostridium difficile myovirus, phiCDHM1, contains homologs of three bacterial accessory gene regulator (agr) genes. The agr system is a type of quorum sensing (QS), via which the phage may modify C. difficile interactions with its environment. Although their mechanism of action is unknown, mutants in bacterial versions of these genes impact sporulation and virulence. To explore how phage QS genes may influence C. difficile biology, we examine the main categories of bacterial behavior that phages have been shown to influence and discuss how interactions via QS could influence behavior at a wider level.