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Molecular and cellular interactions between the plant protective bacterium Bacillus subtilus 49b and the plant pathogen Fusarium oxysporum causing tomato root and foot rot


Fungal attack leads to major agricultural crop losses. Use of chemical pesticides to suppress fungal pathogens forms a threat to the environment and human health since some of these pesticides are very persistent and hazardous. Development of environmental friendly disease control strategies, such as biological control based on the use of protective microorganims, is highly required.

The efficacy of biocontrol agents (when applied as an inoculant) is not always consistent. Fundamental knowledge on the inter actions between the fungus and the biocontrol bacterium is required to understand how the biocontrol bacterium functions at the cellular and molecular level, which forms the basis for the biocontrol effect, and which will contribute to an improved inoculum application.

This study will focus on the biocontrol bacterium Bacillus subtilus strain 49b, which is able to protect tomato roots against the attack of the phytopathogenic fungus Fusarium oxysporum. Bacillus bacteria are very suited for inoculum production since they form heat and drought resistant spores. One of the mechanism through which biocontrol of strain 49b might function is its production of anti fungal metabolites (antibiotics), which after a first analysis seem to be of an unknown class.

The project aims at an integrative approach of biochemical, genetic and microscopic analyses to elucidate the biocontrol mechanism(s) of B. subtilus strain b49. State of the art equipment and methods, including confocal laser scanning microscopy and microarray analysis, will be applied to study the interaction of B. subtilus with the target fungus on the tomato root.

The project will result in the identification of the anti fungal metabolites, elucidate their relevance for biocontrol, identify genes that are relevant for biocontrol ability of B. subtilus. Microscopy studies will visualize the interactions between B. subtilus strain 49b (and mutant derivates) and F. oxysporum at the cellular level.

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Rapenburg 70