Phage or foe?

In light of new evidence, we have to reassess the role of bacteriophages in microbial communities: are they always the enemy?

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Time and time again, the microbial world reveals a surprising degree of complexity. In that sense, the study of bacteriophages, viruses that infect bacteria, has proven to be no exception. The interactions between phages and their bacterial hosts display intricate patterns of mutual control and co-evolutionary  processes worthy of any predator-prey dicotomy from the macroscopic world. This article presents different facets of phage-bacteria interactions that have been recently unveiled. On the one hand, recent work confirms that phage pressure can enhance biofilm formation, virulence or antibiotic resistance in bacterial populations. This phenomenon needs to be carefully considered in the context of phage therapy. Experience from the use of antibiotics has already shown the nefarious consequences of neglecting bacterial responses and evolutionary changes when cells are under pressure from external challenges. Additionally, application of omics techniques to phage research has enabled us to start decoding the complex  responses of bacterial cells to viral infection. Moreover, some of the most recent studies have shed light on the interconnection between phage resistance and quorum-sensing signalling pathways. This finding further hints at the importance of the interplay between bacteria and bacteriophages for the development of microbial communities.  Altogether, the data obtained so far highlights the need for more research to get a clearer picture of how viral predation affects the establishment and evolution of natural microbial populations. With this in mind, the overall message of this review is that phage pressure may be deleterious for single cells but benefitial for the population at large, a fine-tuned balance that needs to be well characterized and considered in order to exploit the antimicrobial potential of bacteriophages.



Since their discovery, bacteriophages have been traditionally regarded as the natural enemies of bacteria. However, recent advances in molecular biology techniques, especially data from "omics" analyses, have revealed that the interplay between bacterial viruses and their hosts is far more intricate than initially thought. On the one hand, we have become more aware of the impact of viral predation on the composition and genetic makeup of microbial communities thanks to genomic and metagenomic approaches. Moreover, data obtained from transcriptomic, proteomic, and metabolomic studies have shown that responses to phage predation are complex and diverse, varying greatly depending on the bacterial host, phage, and multiplicity of infection. Interestingly, phage exposure may alter different phenotypes, including virulence and biofilm formation. The complexity of the interactions between microbes and their viral predators is also evidenced by the link between quorum-sensing signaling pathways and bacteriophage resistance. Overall, new data increasingly suggests that both temperate and virulent phages have a positive effect on the evolution and adaptation of microbial populations. From this perspective, further research is still necessary to fully understand the interactions between phage and host under conditions that allow co-existence of both populations, reflecting more accurately the dynamics in natural microbial communities.


Phage or foe: an insight into the impact of viral predation on microbial communities.  

Lucía Fernández, Ana Rodríguez, Pilar García.

ISME J. 2018 Jan 25. doi: 10.1038/s41396-018-0049-5. 

Lucía Fernández

Postdoctoral researcher, Instituto de Productos Lácteos de Asturias (IPLA-CSIC)