Representative time-courses of the survival of wild-type N2 worms (closed squares) and dbl-1(nk3) mutants (open squares) grown under standard conditions on OP50 and transferred at the L4 stage to plates containing 400 microgrammes/ml 5-fluoro-2'deoxyuridine (FUDR), which blocks DNA synthesis and prevents bacterial replication, spread with OP50. 50 worms were used for each test.