Biological validation of identified genes.

Wild-type (N2) and mutant C. elegans strains were grown on the four bacterial isolates and absolute fitness (λ) and time to death for 50% of the individuals in a population (TD50 in days) was measured. P-values are shown for contrasts between environments within strain for λ and TD50. Standard error (s.e.m.) is given in parenthesis. + indicates a significant (P<0.05) increase relative to wild type and − indicates a significant (P<0.05) decrease of the mutant relative to wild-type.