Figure 8.

Mutants of the Xanthomonas oryzae pv. oryzae (Xoo) chemotaxis component exhibit altered siderophore production and sensitivity to streptonigrin (SNG). (A) Representative photographs of siderophore production assay by different strains of Xoo. Siderophore production is indicated by the presence of an extended halo around the colony grown on peptone–sucrose agar (PSA) plates containing chrome azurol sulphonate (CAS) + 50 µm 2,2′‐dipyridyl (PSA‐CAS + DP). (B) Quantification of siderophore production. The average ratio of siderophore halo to colony diameter for different strains of Xoo grown on PSA‐CAS‐DP plates. (C) SNG sensitivity plate assay. Different strains of Xoo were grown in peptone–sucrose (PS) medium at a density of 1 × 10⁹ cells/mL. Cultures (4 μL) from each serial dilution were spotted onto PSA plates containing 0.02 μg/mL SNG. Plates were incubated for 72 h at 28 °C to observe bacterial growth. Data are shown as the mean ± standard deviation (SD) (n = 3). *^,**Statistically significantly different values compared with the wild‐type strain (Student’s t‐test; *P < 0.01, **P < 0.001). The experiments were repeated at least three times. [Colour figure can be viewed at wileyonlinelibrary.com]