Killing by Type VI secretion drives genetic phase separation and correlates with increased cooperation.
By nature of their small size, dense growth and frequent need for extracellular metabolism, microbes face persistent public goods dilemmas. Genetic assortment is the only general solution stabilizing cooperation, but all known mechanisms structuring microbial populations depend on the availability of free space, an often unrealistic constraint. Here we describe a class of self-organization that operates within densely packed bacterial populations. Through mathematical modelling and experiments with Vibrio cholerae, we show how killing adjacent competitors via the Type VI secretion system (T6SS) precipitates phase separation via the 'Model A' universality class of order-disorder transition mediated by killing. We mathematically demonstrate that T6SS-mediated killing should favour the evolution of public goods cooperation, and empirically support this prediction using a phylogenetic comparative analysis. This work illustrates the twin role played by the T6SS, dealing death to local competitors while simultaneously creating conditions potentially favouring the evolution of cooperation with kin.
Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK.|Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK.
Luke
L
McNally
School of Biological Sciences, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Eryn
E
Bernardy
School of Biological Sciences, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Jacob
J
Thomas
School of Physics, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Arben
A
Kalziqi
School of Biological Sciences, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Jennifer
J
Pentz
School of Biological Sciences, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Sam P
0000-0003-1892-9275
SP
Brown
School of Biological Sciences, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Brian K
BK
Hammer
School of Physics, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
Peter J
PJ
Yunker
School of Biological Sciences, Georgia Institute of Technology. Atlanta, Georgia 30332, USA.
William C
WC
Ratcliff
D000898:Antibiosis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005075:Biological Evolution; D019295:Computational Biology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D016680:Genome, Bacterial / Q000502:physiology; D008954:Models, Biological; D010802:Phylogeny; D000069376:Type VI Secretion Systems / Q000502:physiology*; D014734:Vibrio cholerae / Q000502:physiology*
D001426:Bacterial Proteins; D000069376:Type VI Secretion Systems