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Proc Natl Acad Sci U S A. 2018 Jan 9;115(2):337-342. doi: 10.1073/pnas.1708954115. Epub 2017 Dec 19.

A growing microcolony can survive and support persistent propagation of virulent phages.

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Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark.
Department of Biology, University of Copenhagen, DK-2200 Copenhagen, Denmark
Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark;


Bacteria form colonies and secrete extracellular polymeric substances that surround the individual cells. These spatial structures are often associated with collaboration and quorum sensing between the bacteria. Here we investigate the mutual protection provided by spherical growth of a monoclonal colony during exposure to phages that proliferate on its surface. As a proof of concept we exposed growing colonies of Escherichia coli to a virulent mutant of phage P1. When the colony consists of less than [Formula: see text]50,000 members it is eliminated, while larger initial colonies allow long-term survival of both phage-resistant mutants and, importantly, colonies of mostly phage-sensitive members. A mathematical model predicts that colonies formed solely by phage-sensitive bacteria can survive because the growth of bacteria throughout the colony exceeds the killing of bacteria on the surface and pinpoints how the critical colony size depends on key parameters in the phage infection cycle.


bacteria; coexistence; endemic; predator-prey; spatial structure

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