Herd immunity, a process in which resistant individuals limit the spread of a pathogen among susceptible hosts has been extensively studied in eukaryotes. Even though bacteria have evolved multiple immune systems against their phage pathogens, herd immunity in bacteria remains unexplored. Here we experimentally demonstrate that herd immunity arises during phage epidemics in structured and unstructured Escherichia coli populations consisting of differing frequencies of susceptible and resistant cells harboring CRISPR immunity. In addition, we develop a mathematical model that quantifies how herd immunity is affected by spatial population structure, bacterial growth rate, and phage replication rate. Using our model we infer a general epidemiological rule describing the relative speed of an epidemic in partially resistant spatially structured populations. Our experimental and theoretical findings indicate that herd immunity may be important in bacterial communities, allowing for stable coexistence of bacteria and their phages and the maintenance of polymorphism in bacterial immunity.
We are grateful to Remy Chait for his help and assistance with establishing our experimental setups and to Tobias Bergmiller for valuable insights into some specific experimental details. We thank Luciano Marraffini for donating us the pCas9 plasmid used in this study. We also want to express our gratitude to Seth Barribeau, Andrea Betancourt, Călin Guet, Mato Lagator, Tiago Paixão and Maroš Pleška for valuable discussions on the manuscript. Finally, we would like to thank the editors and reviewers for their helpful comments and suggestions.
Payne P, Geyrhofer L, Barton NH, Bollback JP. CRISPR-based herd immunity can limit phage epidemics in bacterial populations. eLife. 2018;7. doi:10.7554/eLife.32035
Payne, P., Geyrhofer, L., Barton, N. H., & Bollback, J. P. (2018). CRISPR-based herd immunity can limit phage epidemics in bacterial populations. ELife, 7. https://doi.org/10.7554/eLife.32035
Payne, Pavel, Lukas Geyrhofer, Nicholas H Barton, and Jonathan P Bollback. “CRISPR-Based Herd Immunity Can Limit Phage Epidemics in Bacterial Populations.” ELife 7 (2018). https://doi.org/10.7554/eLife.32035.
P. Payne, L. Geyrhofer, N. H. Barton, and J. P. Bollback, “CRISPR-based herd immunity can limit phage epidemics in bacterial populations,” eLife, vol. 7, 2018.
Payne P, Geyrhofer L, Barton NH, Bollback JP. 2018. CRISPR-based herd immunity can limit phage epidemics in bacterial populations. eLife. 7, e32035.
Payne, Pavel, et al. “CRISPR-Based Herd Immunity Can Limit Phage Epidemics in Bacterial Populations.” ELife, vol. 7, e32035, eLife Sciences Publications, 2018, doi:10.7554/eLife.32035.
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