Isolation of thermophilic Actinobacteria from compost and identification of bioactive compounds with antimicrobial properties

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To combat the problem of antimicrobial resistance, we are testing the hypothesis that thermophilic Actinobacteria produce novel antimicrobials at higher temperatures, with potential activity against life-threatening infections like invasive aspergillosis caused by the fungus Aspergillus fumigatus. Samples from “windrows” at a green waste processing facility yielded 36 potential thermophilic Actinobacterial strains isolated at 50oC, as well as strains of A. fumigatus. The phylogeny and identities of the bacterial strains were determined by 16S rDNA sequencing. Three strains - DJT 15 Streptomyces thermoviolaceus subsp. apingens, DJT 32 Saccharomonospora viridis and DJT 36 Saccharomonospora glauca - have shown inhibitory activity in bioassays against the ESKAPE pathogens, two of which (DJT 32 and 36) also inhibited the growth of the fungal pathogen Aspergillus fumigatus isolated from the same compost. Strain DJT 32 has also been shown to have an inhibitory effect against azole resistant human pathogenic strains of A. fumigatus. Whole genome Sequencing data of DJT 15 and 32 have been used to identify possible biosynthetic gene clusters for antimicrobial compounds (novel or otherwise) through AntiSmash analysis. Alongside this, bioactive compounds have been extracted from broth cultures of each strain using HP-20 Resin method, and the metabolites will be identified using LC:MS combined with metabolic profiling. Extraction and identification of novel metabolites will provide a path for the development of new antimicrobials for clinical use. This study has shown that thermophilic Actinobacteria produce antimicrobial compounds at higher temperatures, against Staphylococcus aureus and against the highly pathogenic fungus, A. fumigatus.