Figure 3. B cell amplification (growth) as a function of toxin adsorption probability for different values of toxin production and toxin diffusion rate.

Toxin adsorption probability (horizontal axis) indicates the probability that a toxin molecule will attach to a C cell when they occupy the same patch; the x = 0 point corresponds to the situation with no toxin. Vertical axis (amplification) is the fold-increase in number of B cells between the beginning and end of the simulation cycle. Toxin production is the number of toxin molecules produced per simulation time step by a B cell, provided it has sufficient energy; toxin diffusion rate is the number of patches that a toxin moves (in a randomly chosen direction) each time step. The dynamic range was highest for the larger diffusion rate and corresponds to an overall 2.78× increase. The simulations were initialized with a 1 : 1 ratio of randomly distributed C to B cells (200 cells each). Other model parameters were toxin duration (the number of simulation time steps that a toxin molecule will remain viable; 3 steps), toxicity (the reciprocal of the number of attached toxin molecules needed to kill a C cell; 1/3), nutrient units per patch (12), nutrient units available per killed cell (.5), simulation time (350 steps). A step corresponds to 3 min.