Assessment of the diversity of algicolous fungi from Prince Edward Island, new species discovery and antimicrobial screening of selected isolates

The field of fungal taxonomy has been enduring in recent years due to the progress and application of molecular tools used in concert with morphological analysis. The fungal kingdom is extremely diverse and estimated to include 1.5 million species. Only 11% of these fungi are currently described in the literature. Marine-derived fungi are an ecological group of fungi that have been under focus lately for the purpose of drug discovery as they produce structurally unique secondary metabolites, most of which display promising biological and pharmacological properties against many human and crop diseases. Fungi derived from Prince Edward Island (PEI) marine habitats represent a potentially valuable resource and have not been investigated for the purpose of discovering both new species and new pharmacologically active secondary metabolites. Thus, the strategy of this thesis research was to isolate algicolous fungi from the south shore of PEI and examine some of the promising isolates for the production of antimicrobial metabolites. The biological diversity in this study encompasses 130 fungal isolates belonging to 35 diverse genera. Almost one third of these isolates are still awaiting discovery and description. A comparative study between sediment and algal fungal content showed that algae present valuable resourceful hosts for the purpose of new species discovery.;Prolonged usage of broad spectrum antibiotics has led to the emergence of drug resistance, necessitating the discovery of novel antimicrobial agents. The rich taxonomic diversity obtained from the biodiversity study initiated investigations into the production of secondary metabolites from selected fungal isolates with the intent to discover novel antimicrobial metabolites, ultimately to be used as lead structures for antimicrobial drug development. Forty-seven isolates were fermented on four nutritionally different media. The extracts were fractionated prior to bioassay and then tested against three "superbugs" in addition to four human pathogens. Fractions from 22 isolates showed moderate to high activity against the selected pathogens. Some of the activity was attributed to previously known metabolites, however this study is thought to be the first report for their activity against the "superbugs". The 47 isolate fermentations has resulted in a total of 531 fractions, this library of fractions is available for the purpose of other biological activity or chemical investigations.;New species discovery with a focus upon algicolous fungi from PEI, was one of the goals of this study. By integrating molecular biology and chemistry, a new fungal species was discovered with the capability of producing secondary metabolites with activity against the "superbugs" methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus . The new species was named Westerdykella reniformis Ebead & Overy sp. nov.; isolated from the red alga Polysiphonia sp. When comparing the chemical and biological profile of this new species relative to other members of the genus, it was obvious that the new species possessed a different natural product biosynthetic gene cluster not previously found in its genus. This finding proves that biodiversity is translated into chemical diversity.