Why Put-Up with Immunity when there is Resistance: An Excursion into the Population and Evolutionary Dynamics of Restriction-Modification and CRISPR-Cas

Bacteria can readily generate mutations that prevent bacteriophage (phage) adsorption and thus make bacteria resistant to infections with these viruses. Nevertheless, the majority of bacteria carry complex innate and/or adaptive immune systems: restriction-modification (RM) and CRISPR-Cas, respectively. Both RM and CRISPR-Cas are commonly assumed to have evolved and be maintained to protect bacteria from succumbing to infections with lytic phage. Using mathematical models and computer simulations, we explore the conditions, under which selection mediated by lytic phage will favor such complex innate and adaptive immune systems, as opposed to simple envelope resistance. The results of our analysis suggest that when populations of bacteria are confronted with lytic phage: (i) In the absence of immunity, resistance to even multiple bacteriophage species with independent receptors can evolve readily. (ii) RM immunity can benefit bacteria by preventing phage from invading established bacterial populations and particularly so when there are multiple bacteriophage species adsorbing to different receptors. (iii) Whether CRISPR-Cas immunity will prevail over envelope resistance depends critically on the length of the co-evolutionary arms race between the bacteria acquiring spacers and the phage generating CRISPR-escape mutants. We discuss the implications of these results in the context of the evolution and maintenance of RM and CRISPR-Cas and highlight fundamental questions that remain unanswered..

Medienart:

Preprint

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

bioRxiv.org - (2020) vom: 18. Jan. Zur Gesamtaufnahme - year:2020

Sprache:

Englisch

Beteiligte Personen:

Gurney, James R [VerfasserIn]
Pleska, Maros [VerfasserIn]
Levin, Bruce R [VerfasserIn]

Links:

Volltext [lizenzpflichtig]
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doi:

10.1101/487132

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

XBI000404799