Evidence for the production of similar toxins by Pseudomonas syringae pv. glycinea and Pseudomonas syringae pv. phaseolicola

Abstract

Systemic chlorotic mottling of trifoliate leaves of soybean cultivars developed following inoculation of unifoliate leaves with strains of Pseudomonas syringae pv. glycinea. This symptom could not be reproduced by application of coronatine, a toxin previously isolated from this bacterium, but resembled systemic symptoms that were produced on bean (Phaseolus vulgaris) by inoculation with P. syringae pv. phaseolicola or by application of toxic principles derived from this pathovar. Attempts to isolate a second toxin from pv. glycinea culture fluids using methods employed for the isolation of phaseolotoxin from pv. phaseolicola were not successful. Evidence was obtained for the presence of inhibitory material that interfered with assays for toxin with Escherichia coli K12 as the test organism. Partial separation of the toxin from the inhibitor and other substances was achieved by high-performance liquid chromatography of culture fluids and further purification was effected by ion exchange, partition, and thin-layer chromatography. Biological activity of the pv. glycinea toxin preparation was similar to a toxin prepared from pv. phaseolicola. Both toxins produced similar systemic symptoms on soybean leaves, inhibited E. coli (reversed by arginine, citrulline, and certain tripeptides), inhibited ornithine carbamoyl transferase, and caused the accumulation of ornithine in soybean leaves, as has been reported for phaseolotoxin. There were small differences between the pv. glycinea and pv. phaseolicola toxins in chromatographic behaviour. It is concluded that, in addition to coronatine, pv. glycinea produces a second toxin that is similar to that produced by pv. phaseolicola.