Bacterial Cheaters Evade Punishment by Cyanide.

Parker Smith,Bryan K Lynn,Martin Schuster,Emanuela Frangipani,Jamison Cozart,Erin Alberts

doi:10.1016/j.isci.2019.07.015

Parker Smith, Bryan K Lynn + Show 4 more

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https://doi.org/10.1016/j.isci.2019.07.015

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Journal: iScience	Publication Date: Jul 16, 2019
Citations: 12	License type: cc-by

Affiliation: Oregon State University, University of Urbino

Abstract

SummaryIn all domains of life, mechanisms exist that protect cooperating groups from exploitation by cheaters. Recent observations with the bacterium Pseudomonas aeruginosa have suggested a paradigmatic cheater control mechanism in which cooperator cells punish or “police” cheater cells by cyanide poisoning. These cheater cells are deficient in a pleiotropic quorum-sensing regulator that controls the production of cooperative secretions including cyanide, and presumably also cyanide resistance. In this study, we directly tested and refuted the cyanide policing model. Contrary to the hypothesis, cheater fitness was unaffected by the presence of cyanide. Cheater mutants grew equally well in co-cultures with either cyanide-proficient or cyanide-deficient cooperators, and they were as resistant to exogenous cyanide as wild-type cells. We show that these behaviors are the result of quorum-sensing-independent and cyanide-responsive resistance gene regulation. Our results highlight the role of genetic architecture in the evolution of cooperative behavior.

Highlights

Cooperative behavior is common in all domains of life, it is intrinsically vulnerable to exploitation by non-cooperating cheats (Hamilton, 1964; Hardin, 1968)
We found that the wild-type and the two quorum sensing (QS) mutants grow more slowly in the presence of cyanide, but we found that the three strains grow well (Figure 2)
We found that cyanide has a dramatic, QS-independent effect on the expression of PA4130’-‘lacZ and PA4133’-‘lacZ (Figure 3)

Summary

Introduction

Cooperative behavior is common in all domains of life, it is intrinsically vulnerable to exploitation by non-cooperating cheats (Hamilton, 1964; Hardin, 1968). There has been great interest in identifying mechanisms that maintain cooperation. A range of different cheater control mechanisms have been described, including limited dispersal, kin discrimination, enforcement, and pleiotropy (Foster et al, 2004, 2007; Ratnieks et al, 2006; Schuster et al, 2013; Travisano and Velicer, 2004). Policing is a type of enforcement in which cooperators punish cheaters (El Mouden et al, 2010; Frank, 1995). Worker policing in the honeybee is the prototypical example. Workers suppress the reproduction of other, selfish workers by eating their eggs (Ratnieks, 1988)

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