Secondary metabolites from broth cultures of fungi associated with dung beetle exoskeletons

Rearing dung beetles in controlled environments is occasionally compromised by growth of entomopathogenic fungi. The communities of such fungi in Australia have not received much attention in the literature; thus, we isolated fungi adhered to the exoskeletons of dung beetles from a laboratory colony as well as those collected from the field.
Fungi from at least 10 taxonomic groups were isolated from Bubas bison, Onthophagus taurus and O. vacca dung beetles, and cultured on potato dextrose broth for 31 days and sampled at 10 and 31 days for metabolic profiling via LC-MS QToF mass spectrometry. Mycelia collected from broth cultures were also extracted separately at 31 days to assess the differences between secreted metabolites and those associated with the fungal intracellular environment.
Broth samples contained chemically diverse secondary metabolites known to be produced by fungi as well as other metabolites associated with other eukaryotic organisms. Mycelial samples typically possessed greater concentrations of metabolites. Metabolic profiles varied greatly with fungal species and to a lesser extent with colony age and intracellular vs extracellular compartments. Among the key metabolites recovered were compounds known to be produced by entomopathogenic species in the genera Penicillium and Samsoniella (e.g., penifulvin A, samsoniellain 2, citrinin and roquefortine C). Further analysis of the rich array of novel and interesting fungal metabolites from the sampled fungal isolates is ongoing.