Characterization of a toxin produced by a rhizobacterialPseudomonas sp. that inhibits wheat growth

Abstract

A toxin produced by a deleterious rhizobacterial pseudomonad that inhibits both winter wheat (Triticum aestivum L.) root andEscherichia coli growth was characterized. The toxin was rapidly deactivated at pH 2 and 12 and by autoclaving (121°C, 15 minutes). Less toxin was destroyed as the temperature and time of exposure decreased, and at 40°C it was stable for at least 24 hours. The toxin was extremely polar and could not be extracted from culture filtrates with organic solvents. The compound eluted after the void volume from a Sephadex G-10 column indicating a molecular weight of less than 700. The toxin adsorbed to Dowex 50W strong cation exchange resin and eluted with 2M NH4OH. Numerous thin layer chromatography solvent systems were unsuccessful at purifying the toxin. The partially purified toxin inhibited several different microorganisms while the producing strains were resistant. The toxin appears unique to toxins produced by recognized plant pathogenic bacteria.