Identification and characterization of Talaromyces purpureogenus for antimicrobial activity

Introduction: Fungi are a rich source of secondary metabolites that potentially could be used as chemotherapeutic, immunomodulatory, or antimicrobial agents. Penicillin was first extracted from a fungus almost one hundred years ago. This revolutionized the field of medicine and saved countless lives. Unfortunately, pathogenic bacteria and fungi have become resistant to the current arsenal of antimicrobial medications and the need for new and novel antimicrobials is becoming urgent. In this study we have isolated a strain of Talaromyces purpureogenus and have begun to characterize its antimicrobial properties. These fungi have been recognized as producers of metabolites with antimicrobial, anticancer, and antioxidant properties.

Methods: Originally, we found a fungal contaminant with typical mold-like growth on a Sabouraud Dextrose agar (SDA) plate co-culture of Bacillus subtilis and Candida albicans. The mold exhibited a distinct red pigmentation of the agar and showed the inhibition of B. subtilis and C. albicans. The isolate was purified by subculturing on SDA and its genomic DNA was isolated for molecular typing by sequencing of the internal transcribed spacer (ITS) regions in the ribosomal RNA gene loci. Characterization of the red coloration surrounding agar colonies of the isolate was initiated using solubility experiments. We also have started challenge studies evaluating the isolate for antimicrobial activities in co-cultures with Lactobacillus strains, B. subtilis, and other fungi such as Candida albicans and Rhizomucor pusillus.

Results: Sanger sequencing of the ITS PCR amplicons generated with the ITS-1 - ITS-4 primer pair revealed sequence identity with Talaromyces purpureogenus database entries. Our isolate’s secretion of red water-soluble dye and its morphology are consistent with published literature on this fungus. The initial challenge studies have revealed that the T. purpureogenus isolate exhibits antimicrobial activities towards bacteria and fungi.

Conclusion: We isolated a strain of T. purpureogenus that shows antagonistic effects towards other microbes. It will be essential to confirm these activities with other microbial challenge assays and isolate the growth inhibitory metabolite(s) for further characterization. Future studies will include the isolation of these active compounds by biochemical methods such as fractionation by Reverse Phase High Performance Liquid Chromatography (HPLC). The resulting fractions will be employed in challenge studies to determine which fractions reveal antimicrobial properties. Mass spectrometry will be used for the identification of active components. The T. purpureogenus strain identified in this study could be a potential resource for designing novel antimicrobials.