Phenotypic Heterogeneity and the Evolution of Bacterial Life Cycles
Fig 4
Colony expansion and cell death.
(Left) Scheme showing the sequential stages of colony fission: (1) cell death, (2) cell differentiation, (3) cell division. Red and blue cells are sticky and non-sticky cells, respectively. (Right) Competition between three genotypes that differ in the death rate of sticky cells: 0% (red line), 5% (blue line) or 10% (green line) chance of cell death. Rate of cell death of non-sticky cells is the same for all genotypes (Pd = 10%). The average frequency ± SD (n = 10) is shown for each genotype over 10.000 time steps. The average population size (black line) is shown with respect to the total carrying capacity (including surface and liquid). At onset of competition, the population in the liquid is saturated (5.000 cells) and on the surface 100 cells of each genotype are randomly placed. Population growth is characterized by two phases: (A) population growth before the inflection point (i.e. colonization stage) and (B) population growth after the inflection point (i.e. climax stage). (Lower) Representative surfaces at different stages of competition. Colours correspond to the different genotypes (red = 0% death rate, blue = 5% death rate, green = 10% death rate). The cells with grey and black outline are non-sticky and sticky cells, respectively. Simulations were performed under low migration rate from the liquid to the surface (Pm = 0.01).