Ammonium-Acetate Is Sensed by Gustatory and Olfactory Neurons in Caenorhabditis elegans
(A) Diagram of the assay. Droplets of attractant and negative control solutions were placed on opposite sides of plate at the locations indicated by the eccentric black dots. To manipulate effective NH4Ac concentrations, rather than changing NH4Ac concentration we changed the droplet volumes as indicated in panels B and C. NH4Ac concentration was 7.5 M and adjusted to pH = 6.0 with acetic acid. Sodium-azide was added to immobilize worms reaching either location. Worms were placed at the center of plate and allowed to move for one hour after which worms in zones A, B, and C were counted and the chemotaxis index (C.I.) was computed as shown. (B) Chemotaxis index vs. droplet volume for NH4Ac placed directly on the assay plate immediately before the assay. (C) Chemotaxis index vs. droplet volume for NH4Ac suspended from the Petri plate lid immediately before the assay. (D) Chemotaxis index for equal volumes (10 µL) of different attractants suspended from the lid. In all panels, H2O refers to a negative control in which only water was spotted on the plate. The concentration of NH4Ac in the droplets was 7.5 M (pH = 6.0). Each bar represents the mean of at least 8 independent assays. Statistics: * p<0.05 and ** p<0.01 in a one way ANOVA with Dunnet's post test comparing all means to the negative control (H2O at both spots).