Phenotypic heterogeneity implements a game theoretic mixed strategy in a clonal microbial population

Genetically identical cells in microbial populations often exhibit a remarkable degree of phenotypic heterogeneity even in homogenous environments. While such heterogeneity is often thought to be a bet-hedging strategy against unpredictable environments, evolutionary game theory also predicts phenotypic heterogeneity as a stable response to evolutionary "hawk-dove" games, in which rare strategies are favored over common ones. Here we provide experimental evidence for this game theoretic explanation in the context of the well-studied yeast GAL network. In an environment containing the two sugars glucose and galactose, the yeast GAL network displays stochastic bimodal activation. We show that genetic mutants playing the "pure" strategies of GAL-ON or GAL-OFF can each invade the opposite strategy when rare, indicating a hawk-dove game between the two. Consistent with the Nash equilibrium of an evolutionary game, the stable mix of pure strategists does not necessarily maximize the growth of the overall population. We also find that the wild type GAL network can invade populations of both pure strategists while remaining uninvasible by either. Taken together, our results provide experimental evidence that evolutionary hawk-dove games between identical cells can explain the phenotypic heterogeneity found in clonal microbial populations.

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Mutation rates in seeds and seed-banking influence substitution rates across the angiosperm phylogeny

10.1101/156398 ◽

2017 ◽

Cited By ~ 4

Author(s):

Marcel Dann ◽

Sidonie Bellot ◽

Sylwia Schepella ◽

Hanno Schaefer ◽

Aurélien Tellier

Keyword(s):

Seed Storage ◽

Branch Length ◽

Population Diversity ◽

Bet Hedging ◽

Novel Mutations ◽

Hedging Strategy ◽

Substitution Rates ◽

Unpredictable Environments ◽

Nuclear Its ◽

Selection Generation

Summary1)BackgroundSeed-banking (the ability to persist in the soil over many generations) is usually considered as a dormant stage where genotypes are “stored” as a bet-hedging strategy in response to unpredictable environments. However, seed dormancy may instead have consequences for the integrity of the DNA and generate novel mutations.2)MethodsWe address this paradox by building phylogenies based on the plastomes and nuclear ITS of species belonging to ten angiosperm clades. In each clade, the substitution rate (branch-length) of a seed-banking species is compared with that of a closely-related non-seed-banking species.3)ResultsSeed-banking species show as high or higher substitution rates than non-seedbanking species, and therefore mutations occur in dormant seeds at a rate at least as high as in above-ground plants. Moreover, seed born mutations have the same probability to reach fixation as those from above ground. Our results are robust to differences in selection, generation time, and polymorphism.4)ConclusionsMutations occurring in seeds, and thus seed-banking, affect the population diversity of plant species, and are observable at the macro-evolutionary scale. Our study has consequences for seed storage projects, since the stored seeds are likely to accumulate mutations at a higher rate than previously thought.

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Phenotypic heterogeneity is adaptive for microbial populations under starvation

10.1101/2021.04.05.438545 ◽

2021 ◽

Author(s):

Monika Opalek ◽

Bogna Smug ◽

Michael Doebeli ◽

Dominika Magdalena Wloch-Salamon

Keyword(s):

Nutrient Recycling ◽

Phenotypic Heterogeneity ◽

Microbial Populations ◽

Lag Phase ◽

Starvation Period ◽

Quiescent State ◽

Bet Hedging ◽

Quiescent Cells ◽

Variable Environments ◽

Over Time

To persist in variable environments populations of microorganisms have to survive periods of starvation and be able to restart cell division in nutrient-rich conditions. Typically, starvation signals initiate a transition to a quiescent state in a fraction of individual cells, while the rest of the cells remain non-quiescent. It is widely believed that, while quiescent cells (Q) help the population to survive long starvation, the non-quiescent cells (NQ) are a side effect of imperfect transition. We analysed regrowth of starved monocultures of Q and NQ cells compared to mixed, heterogeneous cultures in simple and complex starvation environments. Our experiments, as well as mathematical modelling, demonstrate that Q monocultures benefit from better survival during long starvation, and from a shorter lag phase after resupply of rich medium. However, when the starvation period is very short, the NQ monocultures outperform Q and mixed cultures, due to their short lag phase. In addition, only NQ monocultures benefit from complex starvation environments, where nutrient recycling is possible. Our study suggests that phenotypic heterogeneity in starved populations could be a form of bet hedging, which is adaptive when environmental determinants, such as the length of the starvation period, the length of the regrowth phase, and the complexity of the starvation environment vary over time.

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Obligate annual and successive facultative diapause establish a bet-hedging strategy of Rhagoletis cerasi (Diptera: Tephritidae) in seasonally unpredictable environments

Physiological Entomology ◽

10.1111/phen.12206 ◽

2017 ◽

Vol 42 (3) ◽

pp. 225-231 ◽

Cited By ~ 4

Author(s):

Cleopatra A. Moraiti ◽

Nikos T. Papadopoulos

Keyword(s):

Bet Hedging ◽

Hedging Strategy ◽

Unpredictable Environments ◽

Rhagoletis Cerasi

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Evolutionary Stabilization of Cooperative Toxin Production through a Bacterium-Plasmid-Phage Interplay

mBio ◽

10.1128/mbio.00912-20 ◽

2020 ◽

Vol 11 (4) ◽

Cited By ~ 1

Author(s):

Stefanie Spriewald ◽

Eva Stadler ◽

Burkhard A. Hense ◽

Philipp C. Münch ◽

Alice C. McHardy ◽

...

Keyword(s):

Cooperative Behavior ◽

Temperate Phage ◽

Phenotypic Heterogeneity ◽

Model Organisms ◽

Bet Hedging ◽

Hedging Strategy ◽

Specific Lysis ◽

Bacterial Populations ◽

Content Type ◽

Group B

ABSTRACT Colicins are toxins produced and released by Enterobacteriaceae to kill competitors in the gut. While group A colicins employ a division of labor strategy to liberate the toxin into the environment via colicin-specific lysis, group B colicin systems lack cognate lysis genes. In Salmonella enterica serovar Typhimurium (S. Tm), the group B colicin Ib (ColIb) is released by temperate phage-mediated bacteriolysis. Phage-mediated ColIb release promotes S. Tm fitness against competing Escherichia coli. It remained unclear how prophage-mediated lysis is realized in a clonal population of ColIb producers and if prophages contribute to evolutionary stability of toxin release in S. Tm. Here, we show that prophage-mediated lysis occurs in an S. Tm subpopulation only, thereby introducing phenotypic heterogeneity to the system. We established a mathematical model to study the dynamic interplay of S. Tm, ColIb, and a temperate phage in the presence of a competing species. Using this model, we studied long-term evolution of phage lysis rates in a fluctuating infection scenario. This revealed that phage lysis evolves as bet-hedging strategy that maximizes phage spread, regardless of whether colicin is present or not. We conclude that the ColIb system, lacking its own lysis gene, is making use of the evolutionary stable phage strategy to be released. Prophage lysis genes are highly prevalent in nontyphoidal Salmonella genomes. This suggests that the release of ColIb by temperate phages is widespread. In conclusion, our findings shed new light on the evolution and ecology of group B colicin systems. IMPORTANCE Bacteria are excellent model organisms to study mechanisms of social evolution. The production of public goods, e.g., toxin release by cell lysis in clonal bacterial populations, is a frequently studied example of cooperative behavior. Here, we analyze evolutionary stabilization of toxin release by the enteric pathogen Salmonella. The release of colicin Ib (ColIb), which is used by Salmonella to gain an edge against competing microbiota following infection, is coupled to bacterial lysis mediated by temperate phages. Here, we show that phage-dependent lysis and subsequent release of colicin and phage particles occurs only in part of the ColIb-expressing Salmonella population. This phenotypic heterogeneity in lysis, which represents an essential step in the temperate phage life cycle, has evolved as a bet-hedging strategy under fluctuating environments such as the gastrointestinal tract. Our findings suggest that prophages can thereby evolutionarily stabilize costly toxin release in bacterial populations.

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Generalized Replicator Dynamics as a Model of Specialization and Diversity in Societies

Advances in Complex Systems ◽

10.1142/s0219525998000211 ◽

1998 ◽

Vol 01 (04) ◽

pp. 325-359 ◽

Cited By ~ 1

Author(s):

Vivek S. Borkar ◽

Sanjay Jain ◽

Govindan Rangarajan

Keyword(s):

Mixed Strategy ◽

Replicator Dynamics ◽

Pure Strategy ◽

Evolutionary Game ◽

Payoff Matrix ◽

Theoretic Model ◽

Final States ◽

Game Theoretic ◽

Game Theoretic Model ◽

Pure Strategies

We consider a generalization of replicator dynamics as a non-cooperative evolutionary game-theoretic model of a community of N agents. All agents update their individual mixed strategy profiles to increase their total payoff from the rest of the community. The properties of attractors in this dynamics are studied. Evidence is presented that under certain conditions the typical attractors of the system are corners of state space where each agent has specialized to a pure strategy, and/or the community exhibits diversity, i.e., all strategies are represented in the final states. The model suggests that new pure strategies whose payoff matrix elements satisfy suitable inequalities with respect to the existing ones can destabilize existing attractors if N is sufficiently large, and be regarded as innovations that enhance the diversity of the community.

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