FIG 3.
The ΔpaaK1 ΔpaaK2 mutant is more virulent than the wild type in C. elegans and has higher proteolytic activity. (A) Slow-killing assays with C. elegans over a period of 7 days show that the ΔpaaK1 ΔpaaK2 mutant kills C. elegans in a similar time frame as the wild type, whereas the nematodes exposed to the ΔpaaABCDE mutant have increased survival (n = ∼70 to 100 nematodes per strain). The increased killing ability of the ΔpaaK1 ΔpaaK2 mutant compared to that of the wild type was determined as significant according to a log rank test (P < 0.001). Three biological replicates were performed. (B) Proteolytic activity was measured as the area of the zone of clearance (excluding colonies) on agar containing 2% skim milk with or without the addition of 2 mM phenylalanine. The error bars represent the standard deviations of three independent experiments. *, P < 0.05; **, P < 0.01 (comparing results to those with the wild type).