Dihydrorhizobitoxine, a minor product of Pseudomonas andropogonis

Abstract

A minor product of the bacterial plant pathogen ‘ Pseudomonas andropogonis’ was isolated and purified, and identified as dihydrorhizobitoxine by mass and NMR spectroscopy by comparison with authentic material. The production of dihydrorhizobitoxine from a total of five rhizobitoxine-producing strains of P. andropogonis was established by isolation and purification of the compound and comparison with authentic dihydrorhizobitoxine. In contrast, three strains of P. andropogonis that did not produce rhizobitoxine, also failed to produce dihydrorhizobitoxine. When P. andropogonis was fed 4- 13C-aspartic acid, the dihydrorhizobitoxine had a four-fold enrichment at C-4, as has been found with rhizobitoxine, and shows the specific utilization of aspartic acid in the biosynthesis of dihydrorhizobitoxine. A ∼1.8-fold enrichment at C-1 of dihydrorhizobitoxine most likely occurred by mixing of carbons 1 and 4 of aspartic acid through the action of fumarase. Implications for the biosynthesis of both rhizobitoxine and dihydrorhizobitoxine are discussed.