|Hassan, Karl -|
|Paulsen, Ian -|
Submitted to: Australian Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: April 8, 2010
Publication Date: July 4, 2010
Citation: Hassan, K., Loper, J.E., Paulsen, I. 2010. Genomic basis of plant pathogen suppression by biocontrol Pseudomonas species. Australian Society for Microbiology Meeting Program Book. Technical Abstract: Various plant commensal bacterial species, which naturally colonize the plant rhizosphere, are able to suppress fungal, bacterial, viral and even insect plant pathogens. These biocontrol activities are elicited primarily through the production of secreted exoenzymes and secondary metabolites that may function as antibiotics, biocides, signaling molecules and/or siderophores. Rhizosphere Pseudomonas spp. are amongst the most prolific secondary metabolite producers and display great promise as agriculturally applicable biocontrol agents. Effective biocontrol relies on the coordinated expression of numerous biocontrol elements and is sensitive to both environmental conditions and the physiological state of the organism. To study the regulatory pressures dictating expression of biocontrol elements, we developed a whole genome microarray for the model biocontrol pseudomonad, Pseudomonas fluorescens Pf-5. This microarray was used to examine the transcriptomic responses of knockout mutations to known secondary metabolism regulators such as the gacA response regulator. In addition to modulating secondary metabolite and exoenzyme expression, disruption of the gacA gene effected pathways involved in important cellular functions, such as iron homeostasis and stress responses, highlighting the interconnectivity of biocontrol expression and basic cellular physiology. We have recently determined genome sequences for seven additional biocontrol Pseudomonas spp. These organisms display diverse biocontrol phenotypes, e.g., differential capacities to control specific plant pathogens in particular plant systems. We are mining the genomes of these bacteria to identify the molecular elements, such as secondary metabolite gene clusters, that may explain the distinct phenotypes of these organisms. This information, in combination with the results of our regulatory analyses, is being used to build whole genome systems views of biocontrol in Pseudomonas spp.