FIG. 3.

(A) Expression of argF in the argK mutant background. Shown is a Northern blot of total RNA from P. syringae pv. phaseolicola (Psph) and the argK mutant (UIKcat) grown in M9 medium at 18°C. The blot was hybridized with a radioactively labeled 1.2-kbp fragment of argF. 23S rRNA stained with ethidium bromide is shown as a loading control. The signal of the size expected for a monocistronic argF message is marked. Asterisk indicates the position of a secondary band of ≈2.2 kbp that also hybridizes with argF. (B) Phaseolotoxin production by the argK mutant. Phaseolotoxin produced by P. syringae pv. phaseolicola and the argK mutant grown in M9 medium at 18°C was evaluated by using the E. coli growth inhibition assay. M9, E. coli JM103 plus M9 medium; M9 + R, E. coli JM103 plus M9 medium supplemented with 10 mM arginine.