|De La Fuente, Leonardo|
Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2004
Publication Date: 11/30/2004
Citation: Validov, S., Mavrodi, O., De La Fuente, L., Boronin, A., Weller, D.M., Thomashow, L.S., Mavrodi, D. 2004. Antagonistic activity among 2,4-diacetylphloroglucinol-producing fluorescent pseudomonas spp.fems microbiol. lett.. Fems Immunology and Medical Microbiology. Interpretive Summary: Root diseases caused by soilborne pathogens are major yield-limiting factors in the production of food, fiber and ornamental crops. As agricultural practices become more sustainable and less dependent on chemical inputs, there is an increasing need for ecologically sound methods of disease control. Biological control, which exploits the natural antagonistic activity of certain root-colonizing bacteria against fungal pathogens, is one such approach. The activity of many biocontrol agents depends on production of the antifungal metabolite 2,4-diacetylphloroglucinol(DAPG). However, DAPG-producing strains differ in the efficiency with which they colonize roots, and only the most competitive ones have an important role in take-all decline, a natural biocontrol phenomenon in which symptoms or the wheat root disease take-all subside spontaneously after several consecutive wheat crops. Because efficient root colonization is often a bottleneck to effective biological control and more widespread grower and industry acceptance of the technology, the traits that contribute to the exceptional competitiveness of these unique strains are of great interest. This study focused on the contribution of bacteriocins (protein-containing compounds produced by certain strains of bacteria and which kill closely related strains or species) to the competitiveness of 47 DAPG-producing strains of P. fluorescens. Over 70% of the strains inhibited the growth of other isolates in laboratory assays. In studies on the roots of wheat grown in soil in the greenhouse, populations of sensitive strains declined more rapidly in the presence of antagonistic bacteriocin producers than when the sensitive strains were introduced alone. The results indicate that antagonism associated with the production of bacteriocins can influence the ability of biocontrol agents to establish and maintain effective population densities in situ.
Technical Abstract: Strains of fluorescent Pseudomonas spp. that produce 2,4-diacetylphloroglucinol (2,4-DAPG) differ in their ability to colonize roots. In this study, we screened 47 2,4-DAPG-producing strains representing 17 distinct genotypes for antagonistic activity associated with the production of bacteriocins. Upon induction, over 70% of the strains inhibited the growth of other isolates in vitro. Greenhouse assays indicated that populations of sensitive strains in wheat rhizosphere soil declined more rapidly in the presence of antagonists than when introduced alone. Antagonism can influence the ability of biocontrol agents to establish and maintain effective population densities in situ.