Doctoral Degrees (Biochemistry)

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Browsing Doctoral Degrees (Biochemistry) by Author "Barnard-Jenkins, Bernice"

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    Discovery of novel anti-Candida albicans compounds from environmental bacteria
    (Stellenbosch : Stellenbosch University, 2023-12) Barnard-Jenkins, Bernice; Rautenbach, Marina; Snoep, Jacky L. ; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.
    ENGLISH ABSTRACT: The opportunistic fungal pathogen, Candida albicans (C. albicans), has the ability to colonize different epithelial tissues (e.g. vaginal, intestinal and oral tissues) causing moderate to severe and fatal infections. The fatal infections are due to fungal cells that enter the bloodstream and circulate after being dispersed from their resistant biofilms. Organisms that have adapted to form biofilms are associated with improved tolerance to drugs, which was also found for some drugs in this study. A medium-throughput multiplex assay system (MPAS) has been developed for the in-parallel study of several fungal life-cycle stages of different strains of C. albicans. MPAS was designed to use conventional 96-well plates and 96-pin lids in four different assay layouts. In MPAS, the metabolic activity measurements were used to determine the effect of antimicrobial compounds in assay targeting planktonic cell susceptibility, biofilm prevention, biofilm eradication, as well as susceptibility of cells released from biofilms. MPAS detection limits were further optimized by testing the activity of antimicrobial culture extracts from known bacterial producers on the different C. albicans life stages. The MPAS data showed which producer extracts were more active against certain strains of C. albicans, as well as highlighted which fungal forms are more sensitive to certain culture extracts. This led to the successful application of MPAS to identify active culture extracts of unknown soil microbes against planktonic and biofilm forms of C. albicans for further characterization. Ultra-performance liquid chromatography linked to high resolution tandem mass spectrometry (HR UPLC-MSᵉ) was used to identify and characterize known antifungal lipopeptides (such as surfactins, iturins and fengycins), rhamnolipids, as well as active small quorum sensing compounds in the most active culture extracts. The overall success of the MPAS together with HR UPLC-MSᵉ was confirmed by the successful identification of known and unknown compounds, from soil sample bacteria, with activity against C. albicans. The study showed the potential of the medium throughput MPAS together with HR UPLC-MSᵉ to discover and characterize potential antibiofilm and antifungal compounds for further development.