FIG 5.

Examples of virulence phenotypes observed in the D. discoideum amoeba model. Bacteria (10⁸ CFU) were plated on petri dishes containing HL5 agar with D. discoideum at variable concentrations and examined at day 6. (A) E. coli 536 with 10³ amoebae. Amoebae did not form lysis plaque, indicating a grazing-resistant phenotype. (B) E. coli ErtS with 10³ amoebae. Amoebae did not form lysis plaque. (C) E. coli ErtR with 10³ amoebae. Amoebae did not form lysis plaque. (D) E. coli B REL 606 with 10² amoebae. Amoebae fed on the lawn of bacteria, forming large lysis plaques, in agreement with a grazing-sensitive phenotype.