Lysobacter - Mechanisms of Antagonism

Mechanisms of Antagonism

Originally characterized as a biological control agent for plant diseases, L. enzymogenes strain C3 is unique in that it expresses a wide range of mechanisms contributing to microbial antagonism and biological control that are not shared by all strains of the species. The strain produces numerous extracellular enzymes that contribute to biocontrol activity, including multiple forms of β-1,3-glucanases and chitinases. The strain also has been demonstrated to induce systemic resistance in certain plants, protecting them from pathogen infection. In addition, recent studies have indicated important roles for secondary metabolites with antibiotic activity and biosurfactant activity in fungal antagonism. Several of these traits are globally controlled by a regulator encoded by the clp gene. Mutations in clp are intriguing for two reasons. First, the mutant phenotype implies that a broad range of genes is involved in secreted antimicrobials associated with the clp regulon, many of which remain unidentified. The second is that mutations in clp result in significant loss of extracellular enzyme activities and antimicrobial activity displayed by L. enzymogenes strain C3. These activities normally are phenotypically overwhelming and often lead to masking of other phenotypes in standard assays, making mutation effects of non-related genes difficult or nearly impossible to evaluate. However, strains harboring clp gene mutations provide a means to separate clp-regulated phenotypes from others (such as that describe below), thus making their evaluation feasible. Biological control and mode of actions of disease suppression by Lysobacter spp. has been reviewed Islam 2011