Synergistic interaction between cell wall degrading enzymes and membrane affecting compounds

A number of cell wall degrading enzymes (CWDEs) and cell membrane affecting compounds (MACs) that alter cell membrane structure or permeability have been assayed in vitro against phytopathogenic fungi and bacteria. Osmotin, gramicidin, valinomycin, phospholipase B, trichorzianine A1, trichorzianine B1, gliotoxin, flusilazole, and miconazole were tested in combination with three endochitinases, four exochitinases, and one glucan 1,3-beta-glucosidase from fungi, bacteria, or plants. Every combination of MAC + CWDE showed a high level of inhibition against Botrytis cinerea and Fusarium oxysporum and the interaction between the two kinds of compounds was of a synergistic nature. Different levels of synergism were obtained among the compound combinations depending upon the antifungal activity of the enzyme. When the enzyme treatment was applied subsequent to the MAC, the level of synergism was lower, indicating that degradation of the cell wall is needed to establish the synergistic interaction. The synergism with MACs was also present when the fungal cell wall was altered in a non-enzymatic manner by including L-sorbose in the growth media. The sensitivity of bacterial strains to the two trichorzianines depended upon the nature of their cell wall and could be synergistically enhanced by partial digestion of the wall. Some of the combinations showed a high level of synergism, suggesting that the interaction between MACs and CWDEs could be involved in biocontrol processes and plant self-defense mechanisms