Formation of biofilms under phage predation: considerations concerning a biofilm increase

Abstract

Bacteriophages are emerging as strong candidates for combating bacterial biofilms. However, reports indicating that host populations can, in some cases, respond to phage predation by an increase in biofilm formation are of concern. This study investigates whether phage predation can enhance the formation of biofilm and if so, if this phenomenon is governed by the emergence of phage-resistance or by non-evolutionary mechanisms (eg spatial refuge). Single-species biofilms of three bacterial pathogens (Pseudomonas aeruginosa, Salmonella enterica serotype Typhimurium, and Staphylococcus aureus) were pretreated and post-treated with species-specific phages. Some of the phage treatments resulted in an increase in the levels of biofilm of their host. It is proposed that the phenotypic change brought about by acquiring phage resistance is the main reason for the increase in the level of biofilm of P. aeruginosa. For biofilms of S. aureus and S. enterica Typhimurium, although resistance was detected, increased formation of biofilm appeared to be a result of non-evolutionary mechanisms.

Keywords:

• biofilm
• spatial refuge
• host-parasite
• bacteriophage therapy
• coevolution
• spatial heterogeneity

Acknowledgments

This work is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC Strategic Research Network on Bioactive Paper-SENTINEL) and the Canada Research Chairs (CRC) program. M. Elimelech (Yale University) is acknowledged for providing P. aeruginosa PAO1, and C. O’May (McGill University) is thanked for technical advice and valuable feedback on the manuscript.