Fig. 2. The C. rodentium bottleneck is defined by a fractional relationship between dose and founders.

a Models for the relationship between dose and founding population. In the absence of a bottleneck, all bacteria from the inoculum become founders. If the inoculum contracts due to the limited availability of finite nutrients or niches (e.g. iron, sugar, binding sites), the diversity of the population and thus the size of the founding population will remain fixed once those nutrients are saturated. If increasing dose increases the number of founders, then the underlying mechanism is not due to a limited resource; instead, the bottleneck acts proportionally on the inoculum by eliminating potential founders. b, c C57BL/6 J mice were inoculated with doses ranging from 10⁷ to 10¹⁰ CFU of STAMP-CR253 and the C. rodentium population was monitored in the feces (geometric means and standard deviations; ND not detected counted as 0.5). Additional shedding analysis in Supplemental Fig. 2. c The bottleneck impeding B6 colonization is described 5 days post inoculation by comparing dose and founders with a linear regression of the log₁₀-transformed data (regression line with 95% confidence intervals; not detected counted as 0.8; x-intercept “ID₅₀” 10^7.2–10^7.9 CFU). 4–8 animals per dose. Source data are provided as a Source Data file.