Many beneficial soil and plant endophyte microbes of the Actinobacteria phylum are known for their ability to produce bioactive secondary metabolites. For example, this includes metabolites with antibiotic properties against other microbes such as phytopathogens (1,2,3). However, genome sequencing has revealed these bacteria have far greater potential to produce bioactive compounds than was previously thought based on traditional in vitro bioactivity assays (3,4). It is predicted that these “undetected” compounds may account for up to 90% of Actinobacteria chemical potential (1). This vast hidden potential can be tapped for the discovery of new biopesticides which are needed for the replacement of an increasing number of chemical pesticides that are no longer used owing to 1) toxicity, 2) increasing regulation or 3) increased incidence of resistance in pathogen and pest populations. A collection of Actinobacteria isolated from soils and plant roots from south-west Western Australian environments was curated (5,6). A subset of the collection was screened for inhibitory activity against a diverse panel of fungal phytopathogens with a focus on necrotrophic phytopathogens for which no or limited host resistance has been described. These phytopathogens included members of the Fusarium genus, Verticillium genus, and the broad host range pathogens Rhizoctonia solani and Sclerotinia sclerotiorum; causal agents of Rhizoctonia root and hypocotyl rot, and Sclerotinia stem rot respectively. Coupled with whole genome sequencing and prediction of biosynthetic gene clusters (7), diverse chemical potential was discovered within the selected Actinobacteria strains. Metabolomics and transcriptomics approaches are being combined with the genomics outputs to identify potentially new antifungal secondary metabolites for biopesticide applications.
ACKNOWLEDGEMENTS
Financial support for this work was provided by CSIRO.