Models / Tripartite dynamics (pH & resource)

Tripartite population model with pH and resource dynamics

SFB MibiNet logo Unpublished work done in MibiNet consortium

This model is an unpublished extension of the tripartite Public/Cheater/Private community model. Instead of constant growth rates, each strategy's growth now follows Monod kinetics on an explicit resource: the public metabolizer and private metabolizer grow on sucrose (S), while the cheater grows on extracellular glucose (G) that the public metabolizer releases as a byproduct of sucrose processing.

Every growth rate is additionally scaled by a per-species Gaussian response to environmental pH, fi,H(H) = exp(-(H - Hopt,i)² / (2σH,i²)), so each strategy has its own pH optimum and tolerance width. Dragging the pH slider away from a strategy's optimum suppresses its growth relative to the other two, shifting which strategy dominates the community.

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Simulation parameters

Environmental pH 6
Public max. sucrose growth rate 0.2
Private max. sucrose growth rate 0.18
Cheater max. glucose growth rate 0.2
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Initial conditions

Public Metabolizer 100000
Cheater 100000
Private Metabolizer 100000
Sucrose 20
analytics

Analyses

Time course

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Ecological outcome

Community outcome at t = 50 h

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Model Details

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Generated LaTeX Code

\begin{align*}
  \frac{d \text{Public}}{dt} &= (1 - r) \cdot \mu_{P,S} \cdot \text{Public} \\
  & - \alpha \cdot \text{Public} \cdot \text{Cheater} \\
  & - \beta \cdot \text{Public} \cdot \text{Private} \\
  & - \eta \cdot \text{Public} \cdot \text{Public} \\ 
  \frac{d \text{Cheater}}{dt} &= \mu_{C,G} \cdot \text{Cheater} \\
  & - \nu \cdot \text{Cheater} \cdot \text{Cheater} \\ 
  \frac{d \text{Private}}{dt} &= \mu_{M,S} \cdot \text{Private} \\
  & + \beta \cdot \text{Public} \cdot \text{Private} \\
  & - \gamma \cdot \text{Private} \cdot \text{Private} \\ 
  \frac{d S}{dt} &= - \frac{\mu_{P,S} \cdot \text{Public}}{Y_{P,S}} \\
  & - \frac{\mu_{M,S} \cdot \text{Private}}{Y_{M,S}} \\ 
  \frac{d G}{dt} &= r \cdot \frac{\mu_{P,S} \cdot \text{Public}}{Y_{P,S}} \\
  & - \frac{\mu_{C,G} \cdot \text{Cheater}}{Y_{C,G}}
\end{align*}

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SettingValue
Fit backend
Function evaluations per progress update
Maximum total function evaluations
Stop once residual norm reaches
Curriculum learning (advanced)

Every bar shares one fixed step budget. Drag a divider to move a cutoff, drag a bar's top edge (or focus it and use the arrow keys) to change its share — the final stage isn't draggable, it always gets whatever's left. Double-click a bar or use its + to split it, use a divider's × (or Delete/Backspace while it's focused) to remove it.

Split into equal stages:
min viable
1000 it. (final)
t=0 t=100
StageData cutoffIteration budget
1 (final)full data1000 iterations (runs to convergence within this)

Data

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ParameterFitLog-spaceInitial guess / fixed value Fitted value
Environmental pH —
Public max. sucrose growth rate —
Private max. sucrose growth rate —
Cheater max. glucose growth rate —
Public sucrose half-saturation —
Private sucrose half-saturation —
Cheater glucose half-saturation —
Public pH optimum —
Cheater pH optimum —
Private pH optimum —
Public pH-response width —
Cheater pH-response width —
Private pH-response width —
Public glucose-release fraction —
Cheater burden on Public —
Transfer rate —
Public self-limitation —
Cheater self-limitation —
Private self-limitation —
Public sucrose yield —
Private sucrose yield —
Cheater glucose yield —

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