FIG 4.

Culture extracts from axenic Mycetohabitans sp. kill Protostelium aurantium. (A) The viability of P. aurantium, indicated by the diameter of the predation plaque (clearance of yeast), is significantly reduced in cultures that were exposed to 2% crude culture extract from axenically grown endosymbiotic M. rhizoxinica HKI-0454 (labeled MR) or M. endofungorum HKI-0456 (labeled ME). Incubation with solvent alone (DMSO), extract from culture medium (Ctrl), or rhizoxin-deficient M. rhizoxinica (ΔrhiG) has no effect on the viability of P. aurantium. Circles indicate independent replicated experiments (n = 3) ± 1 SEM (gray bars). One-way ANOVA with Tukey’s multiple-comparison test was performed (****, P < 0.0001; see Table S3). (B) Photographs of yeast agar plates showing the predation plaque by P. aurantium (arrowheads). (C) Liquid survival assay of P. aurantium supplemented with the bacterial rhizoxin S2. Data points represent three independent replicated experiments (n = 3) ± 1 SEM. (D) Microscopic images showing the growth of P. aurantium in the presence of rhizoxin S2. Scale bars, 20 μm.