Thermotolerance assay

Thermotolerance assays were performed as described previously for the single-point survival assay⁷⁶ with the following changes: previously age–synchronized L4 animals were transferred to fresh agar plates of the same bacterial strain and subsequently transferred every other day. Day-5-adults were subjected to heat shock in a water bath at 33 °C (unless otherwise indicated) for the indicated time. After heat shock, worms were shifted to an air incubator at 20 °C and surviving animals were scored after an approximate 20 hour recovery (unless otherwise indicated).

For the experiments with L. rhamnosus GG (ATCC53103) animals were grown on E. coli OP50 until L4 stage, since Lactobacillus do not support C. elegans development. L4-staged worms were treated 3 times with the mix of antibiotics (4 mg/ml carbenicillin and 0.8 mg/ml kanamycin) and then transferred to either L. rhamnosus GG or its biofilm-deficient derivative (ΔspaCBA). Consequently animals were transferred to the fresh plates with corresponding bacterial strains every day until day 5 of adulthood and plates were monitored for potential E. coli OP50 contamination. Worms were subjected to the heat-shock as described earlier.