Taxonomy-guided microbial biodiscovery

Resolution of a microbial culture to the basic taxonomic unit, a species, is often not clear-cut. Strains once considered as robust species have subsequently been shown to be species groups sharing a common phenotype and conserved gene sequences. Increasingly, microbial secondary metabolites are becoming important tools in unravelling microbial biodiversity and taxonomy. As each secondary metabolite is the product of many discrete enzymes, a typical co-metabolite profile represents a significant sub-sample of the functional microbial genome. Comparative analysis of these unique chemical fingerprints offers a rapid and reliable means to identify novel microbial species. In search of novel Australian Aspergilli, we conducted a survey of forest and scrub soils in the South Burnett Region of Queensland. From the ~200 Aspergillus isolates recovered, the phenotype of three strains presented with atypical morphological features with respect to known species in subgenus Circumdati section Circumdati, and were tagged as putative novel species. Significantly, all three isolates had unique secondary metabolite profiles when searched against our in-house database (COMET) of HPLC-DAD traces from >5,000 known or talented fungal species. This presentation will focus on the chemotype of one of these new species, Aspergillus hancockii, isolated from soil in peanut fields near the town of Kumbia. When cultivated on rice as an optimal substrate, A. hancockii produced an extensive array of 69 secondary metabolites. Eleven of the 15 most abundant secondary metabolites, constituting 90% of the total area under the curve of the HPLC trace of the crude extract, were novel.