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Individual-based models of social evolution in biofilms Sara Mitri @ the Foster lab Department of Zoology University of Oxford
Individual-based models of social evolution in biofilms
Sara Mitri
@ the Foster labDepartment of ZoologyUniversity of Oxford
MSc thesis: “The co-evolution of language and behaviour in robots”
PhD thesis: “The evolution of communication in robot societies”
Postdoc proposal: “Spatial patterns and social evolution in bacterial biofilms”
Who am I?
How does evolution shape social behaviour?
What questions am I interested in?
How does evolution shape social behaviour in microbial biofilms?
How does one combine theoretical and
experimental methods to answer these questions?
What role do ecological factors play in the evolution of social
phenotypes in microbial biofilms?
How do spatial patterns in microbial biofilms
influence selection for social phenotypes?
General
Specific
How does the presence of other species in microbial
biofilms influence selection for social phenotypes?
What technology do I use?
Lab experimentsIndividual-based models
How do spatial patterns in microbial biofilms influence selection for social phenotypes?
Picioreanu et al. (2004) Appl & Env MicrobiolXavier et al. (2005) Env Microbiol
1.
Low nutrient concentration High nutrient concentration
Nadell et al. (2010) PLoS Comp Biol
The thickness of the growing edge
Nadell et al. (2010) PLoS Comp Biol
2.
Low nutrient concentration High nutrient concentration
Secretes (costly) beneficial productDoes not secrete beneficial product
Nadell et al. (2010) PLoS Comp Biol
Experiments using Pseudomonas aeruginosa
How does the presence of other species in microbial biofilms influence selection for social phenotypes?
1. “Towers” are no longer sufficient to give an
advantage to secretors.
2. Other species can insulate secretors from
non-secretors, giving them an advantage.
Mitri et al. (in press) PNAS
3. Mutualistic secretions seem unlikely to be selected for.
Mitri et al. (in press) PNAS
Motivation
Challenges
Opportunities
Thanks go to…
Kevin Foster
Carey NadellNuno OliveiraJonas SchluterMarina Caldara
João Xavier Wook Kim
Experiments using Pseudomonas aeruginosa
One species Two species
One species Two species
Two species(species 2 benefits
from secretions)
Two species(species 2 does not
benefit from secretions)
Two species(species 2 benefits
from secretions)
Two species(species 2 does not
benefit from secretions)
Why do secretors do so badlyin the presence of other species under low nutrient conditions?
Hypothesis: competition during initial growth phase
Reducing competition
Reducing competition
1. How do secretors and non-secretors farein the presence of other species?
Secretors can be outcompeted by non-secretorsdue to increased initial competition.
3 questions
2. How do secretors and non-secretors farein the presence of many other species?
3 questions
Equal proportionsof species 1 and 2
Species 2 is initially9 times more abundant
than species 1
Equal proportionsof species 1 and 2
Species 2 is initially9 times more abundant
than species 1
Why does the abundance of other species provide an advantage to secretors over non-secretors?
Hypothesis: other species insulate secretors
Measuring segregation
2. How do secretors and non-secretors farein the presence of many other species?
Secretors can outcompete non-secretorswhen competition is low (e.g., high nutrients)
because other species can separate the two phenotypes.
3 questions
3. How do secretors and non-secretors fareif other species are mutualistic partners?
3 questions
Mutualism between2 species
with self-benefit
Mutualism between2 species
without self-benefit
Mutualism between2 species
with self-benefit
Mutualism between2 species
without self-benefit
Why does mutualism not work?
Hypothesis: when cell types are segregated,
secretors and species 2 cannot benefit from each other;when cell types are mixed, non-secretors benefit
Explaining mutualism
Low nutrients
Secretors Species 2
Non-secretors Species 2
High nutrients
Secretors Species 2
Non-secretors Species 2
Explaining mutualism
3. How do secretors and non-secretors fareif other species are mutualistic partners?
3 questions
Secretors do not do well compared to non-secretorsbecause conditions that favour mutualistic interactions
also maximize benefits of non-secretors.
A case where mutualism “works”
A case where mutualism “works”
3. How do secretors and non-secretors fareif other species are mutualistic partners?
3 questions
2. How do secretors and non-secretors farein the presence of many other species?
1. How do secretors and non-secretors farein the presence of other species?
3 answers
Secretors do not do well compared to non-secretorsbecause conditions that favour mutualistic interactions
also maximize benefits of non-secretors.
Secretors can outcompete non-secretorswhen competition is low (e.g., high nutrients)
because other species can separate the two phenotypes.
Secretors can be outcompeted by non-secretorsdue to increased initial competition.
Not taken into consideration(i.e. future work)
Niche overlapCompetition between speciesRegulation of social behaviour
Competition among groupsBy-product mutualisms
Rela
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