Figure 2.

C. elegans prefers M. xanthus to buffered agar. We tested potential effects of living or dead M. xanthus on the position of worms presented with choices between either two circular patches of M. xanthus (A,B) or between a half-plate lawn of M. xanthus versus a half plate of bacteria-free agar (C,D). For both experiments, we report the mean fraction of C. elegans populations that left the plate (A,C) and the choices made by the worms that remained on the plate (B,D). In panel B, positive vs. negative values reflect attraction to the first- vs. second-listed type of bacteria, respectively. In panel D, positive vs. negative values reflect attraction to the inoculated vs. uninoculated half of the plate, respectively. Each large dot is the mean of five biological replicates (shown as transparent blue dots). Error bars represent 95% confidence intervals. In some instances (B), 95% confidence intervals extend outside the range of what is biologically possible, [−1,1], so we restricted them to reflect the biological reality. ** p < 0.01.