Bacterial Cheaters Evade Punishment by Cyanide

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

doi:10.1016/j.isci.2019.07.015

Bacterial Cheaters Evade Punishment by Cyanide

iScience. 2019 Sep 27:19:101-109. doi: 10.1016/j.isci.2019.07.015. Epub 2019 Jul 16.

Authors

Parker Smith¹, Jamison Cozart¹, Bryan K Lynn², Erin Alberts¹, Emanuela Frangipani³, Martin Schuster⁴

Affiliations

¹ Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA.
² Department of Integrative Biology, Oregon State University, Corvallis, OR 97331, USA.
³ Department of Biomolecular Sciences, University of Urbino "Carlo Bo", 61029 Urbino (PU), Italy.
⁴ Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA. Electronic address: martin.schuster@oregonstate.edu.

Abstract

In 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.

Keywords: Biological Sciences; Evolutionary Biology; Genetics; Microbiology.