Soilborne and invertebrate pathogenic Paecilomyces species show activity against pathogenic fungi and bacteria

The fungal genus Paecilomyces comprises numerous pathogenic and saprobic species, which are regularly isolated from insects, nematodes, soil, air, food, paper and many other materials. Some of the Paecilomyces species have been known to exhibit capabilities for curing human diseases. Here, bioactivities of metabolites from some soil inhabitant and invertebrate pathogenic Paecilomyces species were explored against a panel of target prokaryotic and eukaryotic microorganisms. First, Petri plate assays indicated that all tested Paecilomyces species were capable of producing diffusible metabolites and volatile compounds with antifungal activities against Pyricularia oryzae and Saccharomyces cerevisiae. Subsequently, the metabolites of the Paecilomyces species were extracted and the growth inhibitory and antimitotic effects of extra-cellular metabolites were shown using the yeast S. cerevisiae as a model. Further research indicated some antibacterial activity of extra-cellular metabolites from Paecilomyces species against human pathogenic bacteria Staphylococcus aureus, Bacillus subtilis, Streptococcus pyogenes (G) and Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi (G). These findings indicate that the Paecilomyces species, either saprobic or pathogenic, have a strong arsenal of bioactive metabolites which show inhibitory or cytotoxic effects against other microorganisms, with a potential for application in agroforestry and medicine.