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Title: The isolation and characterisation of genes facilitating iron and copper uptake in Saccharomyces cerevisiae and Candida albicans
Author: Marvin, Marcus Edward
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 2002
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Iron and copper are essential for nearly all known organisms as they are utilised in a wide variety of enzymatic processes. In both prokaryotes and eukaryotes, the metabolism of both metals is often intimately and inseparably linked. The host environment is limiting for Fe and Cu ions and immune-responsive mechanisms have been identified that further reduce available iron upon infection. Therefore, for a pathogen to be successful it must possess mechanisms to acquire copper and especially iron from this hostile environment. Mechanisms that facilitate iron and copper uptake have been described in pathogenic bacteria. However, very little is known how fungal pathogens such as Candida albicans acquire these metals from the host environment. C. albicans is a commensal organism of the skin, vagina and alimentary tract but can cause both localised and fatal systemic infections in the immuno-compromised. Recent evidence has shown that iron acquisition is important for the virulence of this organism. As genetic analysis is difficult in C. albicans, the bakers yeast Saccharomyces cerevisiae can be used as both a model and tool to isolate C. albicans genes. A well-characterised reductive high affinity iron and copper uptake system has been described in S. cerevisiae. This system is transcriptionally regulated in response to the availability of both metals. Interestingly, the acquisition of iron in this organism is dependent upon the acquisition of copper. Recent research has identified that C. albicans possesses a similar system to S. cerevisiae for the acquisition of both metals. This study describes attempts to characterise the C. albicans iron and copper uptake system using S. cerevisiae as both a model and tool. S. cerevisiae mutants defective in iron and copper metabolism were generated in able to isolate and characterise C. albicans genes from genomic DNA libraries. Two types of mutant were used. The first was a UV mutagenised S. cerevisiae strain that was defective in the regulation of cell-surface-associated reductase activity. This mutant was used to isolate novel genes from a S. cerevisiae genomic library with a view to identifying functional homologues in C. albicans. One S. cerevisiae gene is described using this approach, ScLIP2, which was first proposed to be involved in iron metabolism, but was later revealed necessary for the activity of mitochondrial apoproteins. The second S. cerevisiae mutant was defective in high affinity copper uptake and was constructed using targeted gene disruption. This approach used a C. albicans genomic library and led to the description of two genes, CaCTRl and CaMACl, which facilitate high affinity copper uptake in this organism. CaCTRl encodes a protein facilitating the transport of copper across the cell membrane and CaMACl encodes a putative copper-sensing transcription factor that is essential for expression of CaCTRl in deplete copper conditions. Importantly, like its functional homologue in S. cerevisiae, CaCTRl was found to be essential for iron uptake in C. albicans. Therefore, GzCtrlp activity may be important for virulence of C. albicans.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available