Figure 2.

The concentrations of betulin for subsequent experiments were determined with a food clearance assay in Caenorhabditis elegans. Between 20 and 30 newly hatched L1 synchronized worms of N2, BZ555, or OW13 strains were incubated at 25 °C in Escherichia coli (E. coli; OD A₅₉₅ = 0.6), in a 96-well plate containing 0.02, 0.1, 0.5, or 2.5 mM of betulin, to a total volume of 60 µL. The optical density (OD) of the plate was measured daily for 6 d. (A) The OD of E. coli was recorded daily for each concentration of betulin. Data are presented as means ± standard deviations from 3 independent experiments. (B) Concentrations >2.5 mM caused death. Scale bar = 200 μm.