| Secondary metabolites are small molecules produced by microbes to deal with environmental stresses. They are of interest for their physiological importance to the producing organism and for applied use in medicine and agriculture. The traditional method to identify new secondary metabolites involves cultivation of microbes under various growth conditions and screening for desired biological activity. Therefore, discovery of new secondary metabolites is predicated on identification of specific production conditions and the sensitivity of the detection method. While many compounds have been discovered in this manner, it is now clear that the same secondary metabolites are frequently rediscovered. An alternative approach is using whole-genome bioinformatics to predict the potential of an organism for secondary metabolism and access previously unrecognized secondary metabolites.;Most sequenced organisms contain the potential to produce one secondary metabolite and several have the potential to make many more. In those microbes with robust metabolic potential, generally only one of every five potential metabolites has been described. Because the elements necessary to biosynthesize a secondary metabolite are usually clustered and that biosynthesis normally occurs in a predictable fashion, it is often possible to assign a metabolite structure to a given biosynthetic cluster. Characterization of these undescribed metabolites will allow scientists to better understand the physiology and ecology of the producing organism and enlarge the pool of natural products available for pharmaceutical development.;I have focused on the plant pathogen Pseudomonas syringae. These organisms are prolific producers of secondary metabolites and often require strain-specific metabolites for full virulence. Three strains, isolated from tomato, snap bean and Phaseolus bean, have been analyzed in this work, allowing strain-to-strain comparison of secondary metabolic potential. Each isolate has the potential to produce several as-yet uncharacterized metabolites, many of which are unique to a given strain.;This genomics approach to secondary metabolite discovery combines bioinformatics, genetics, biochemistry and analytical chemistry to elucidate metabolic pathways that remained unrecognized using traditional techniques. I have used this multidisciplinary method successfully to discover, isolate and characterize a previously unrecognized biosurfactant secondary metabolite. I have further applied this method to validate production of achromobactin and characterize several enzymes involved in its biosynthesis. |
