Occurrence and nature of antibacterial substances in plants affecting Bacillus thuringiensis and other entomogenous bacteria

Abstract

Antibacterial substances that inhibit the growth of Bacillus thuringiensis var. thuringiensis were found in leaves of 22 plants belonging to pinaceae, Taxaceae, Fagaceae, Salicaceae, Hamamelidaceae, and Leguminosae. These antibacterial substances in leaves of pitch pine, Pinus rigida, Virginia pine, Pinus virginiana, and loblolly pine, Pinus taeda, that were studied in more detail, were found throughout the year. Both old and new growth contained antibacterial substances. It was found that expressed juice from pitch pine foliage inhibited the growth in vitro of all entomogenous bacteria that were tested. In a study of the chemical nature of antibacterial substances in plants, a simplified qualitative analytical method was developed in which pitch pine and Bacillus thuringiensis var. thuringiensis were used as test organisms. Purification and complete separation of the antibacterial material from expressed juice was obtained by ion-exchange column chromatography. A combination of strongly acidic and strongly basic ion-exchange resins were used. Separation of inhibitory material, obtained from ion-exchange chromatography, into five antibacterial substances was achieved by thin-layer chromatography. Silica gel H and solvent system: ethyl acetate, methyl ethyl ketone, formic acid, and distilled water in the ratio 5:3:1:1 were employed. Infrared and ultraviolet spectra and other evidence indicate that these antibacterial substances in pitch pine foliage are possibly hydroxy carboxylic acids.