Submitted to: Medical Mycology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2008
Publication Date: 2/28/2009
Citation: Losada, L., Ajayi, O., Frisvad, J.C., Yu, J., Nierman, W.C. 2009. Effect of Competition on the Production and Activity of Secondary Metabolites in Aspergillus species. Medical Mycology. 47(S1):S88-S96 Interpretive Summary: Aspergilli are opportunistic fungal pathogens most commonly associated with diseases of crops and human and animal systems. Each Aspergillus species can produce a range of secondary metabolites, including aflatoxins associated with fungal growth and development. The mechanisms that regulate production of secondary metabolites are not well understood. It has been shown that several environmental variables have an impact on their production. Apart from environmental signals, competition between different fungal species also modulates production of secondary metabolites. Anti-fungal activities of these secondary metabolites could be used to control fungal infection and to reduce aflatoxin contamination in crops.
Technical Abstract: Secondary metabolites are of intense interest to humans due to their pharmaceutical and/or toxic properties. Aspergillus species secrete these metabolites by themselves and in the presence of other fungal species. Here, we have performed co-cultivation competition assays among different Aspergillus species to determine the fitness of species and to analyze the presence and possible anti-fungal activity of secondary metabolites in extracts. We determined that species fitness depends on competitors, but A. fumigatus and A. terreus are poor competitors in general, while A. flavus is generally a good competitor. Metabolites extracted from the mono-cultivation of A. terreus and A. fumigatus at 30°C and 37°C, and from the co-cultivation of A. clavatus with A. terreus, A. fumigatus, or N. fischeri had the strongest antifungal activities against other Aspergillus species. It appears that different species can act either synergistically or adversarially to produce metabolites with anti-fungal activity. Using gas chromatography, we determined that the composition of extracts changed due to competition. These findings indicate that co-cultivation could be a method for inducing and characterizing novel anti-fungal compounds produced by Aspergillus.