Stochastic assembly produces heterogeneous communities in the Caenorhabditis elegans intestine
(A) Adult AU37 worms fed for 8 d on a 50/50 mixture of dsRed and YFP-labeled E. coli over a range of concentrations from 106–109 CFU/mL show a transition from bimodal to unimodal community composition. Data are pooled from two to three independent experiments (n = 48–56 worms). (B) The transition to bimodality in (A) is confirmed by calculation of the bimodality coefficient (see Methods) for these data (bootstrap confidence intervals over 10,000 runs; red dashed line indicates BCcrit = 0.55) and by direct observation of intestinal communities via fluorescence microscopy. Grey area represents mean ± 1 SD of GSSA simulations exploring the effects of parameter uncertainty (K = (30000, 300000); b = (0.1, 0.6); d = (0.1, 0.5); b > d; see Methods). (C) The transition to bimodality is also observed in an immune-competent strain of C. elegans (glp-4, n = 31–45 worms). This strain possesses the same temperature-sensitive sterile mutation as AU37 but lacks the mutation to immune system function (sek-1). See S1 Data.