Examine Chemoavoidance Behavior in Transgenic Worms Using Osmotic Avoidance Assay

For the osmotic avoidance assay, divide a food-free NGM plate into normal and trap zones, by creating an 8 molar glycerol line in the middle. Then, spread a 200-millimolar sodium azide line at around 1 centimeter away from the glycerol line to paralyze the nematodes crossing through the glycerol barrier into the trap zone.

Transfer around 200 nematodes each onto the normal zone of three replicate plates for each group. Then, add a drop of 1% butanedione onto the trap zone to attract the nematodes. Cover the lid of the Petri dish immediately, and incubate at 23 degrees Celsius for 90 minutes.

Score the number of nematodes on both the zones under a microscope, and calculate the avoidance index.