Functional Genomic Analysis of NaturalProduct Biosynthesis and Secretion inAspergillus fumigatus
Year: 2010
Type: dissertation
Abstract: Aspergillus fumigatus is an opportunistic pathogen which can cause severe\ndisease in immunocompromised patients. A. fumigatus produces metabolites,\nthrough a non-ribosomal peptide synthesis mechanism, including iron-chelating\nmolecules known as siderophores and other unusual compounds such as gliotoxin.\nThese provide the fungus with a unique strategy for survival in the host, and\ncontribute to pathogenicity. The aim of this project was to identify interactions\nbetween non-ribosomal peptide synthetase genes (termed pes1 and sidD) and to\nidentify metabolites produced by these genes, which contribute to the virulence of A.\nfumigatus in immunocompromised patients.\nA. fumigatus pes1 mutants (pes1) were generated in three genetic backgrounds\n(akuB, ATCC46645 and sidD46645), confirmed by Southern blot and qRT-PCR\nanalysis. A. fumigatus akuB:pes1 was significantly more sensitive to oxidative\nstress than wild-type (P < 0.01). It was found that, in vitro, either pes1 or sidD\nsignificantly improved fungal tolerance to anti-fungal drugs (amphotericin B and\nvoriconazole, respectively) which strongly suggests that either gene may play a role\nin mediating drug resistance/tolerance in patients. It was found that under oxidative\nstress conditions that this double mutant was significantly less sensitive to ironlimiting\nconditions than A. fumigatus sidD, indicating that the peptide encoded via\npes1 is involved in the response of siderophore-deficient A. fumigatus to low iron\navailability, such as during infection. Compared to wild-type A. fumigatus,\nsidD:pes1 was significantly less virulent than either single mutant in the Galleria\nmellonella virulence model system. Significantly, pes1 was found to be involved in\nthe biosynthesis of the conidial metabolite, fumigaclavine C, as this metabolite was\nabsent in both A. fumigatus akuB:pes1 and pes146645.\nIn parallel studies, we identified a gene (gliK) responsible for gliotoxin\nbiosynthesis and showed that gliK is involved in protecting A. fumigatus against\noxidative stress, gliotoxin presence and secretion of gliotoxin from A. fumigatus.\nOverall, our findings may lead to improvements in therapy for patients suffering\nfrom invasive aspergillosis in the medium-to long-term.
Author: Lorna Gallagher
Language: English
Subfield: Applied Microbiology and Biotechnology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W85186839