GROUP LEADER: Prof. Marina Rautenbach
Office: A115 JC Smuts Building
PhD, University of Stellenbosch, Biochemistry
MSc, University of Pretoria, Biochemistry
BSc Hons, University of Pretoria, Biochemistry
BSc, University of Pretoria, Chemistry, Biochemistry, Mathematics
Elucidation of the structure-activity relationships, mode of action and resistance towards membrane active antimicrobial compounds.
The Biopep Peptide group investigates resistance towards, mechanism of action and structure-activity relationships (SAR) of antimicrobial peptides and membrane active antibiotics, using both natural and novel synthetic compounds. These antimicrobials are directed against a number of targets such as resistant bacterial pathogens in particular Listeria monocytogenes, fungal plant pathogens, as well as parasites causing malaria (Plasmodium falciparum) and African sleeping sickness (Trypanosoma brucei).
In an ecosystem laden with competing bacteria, fungi and parasites, many strategies of defence have evolved among these organisms in the fight for survival. One of the weapons in host defence is a group of peptides with pronounced antimicrobial activity. For example, various antimicrobial peptides are produced as secondary metabolites by Bacillus species, such as the cyclic iturins, surfactin, gramicidin S and tyrocidines, and the linear gramicidins. Plants, animals and insects also utilise antimicrobial peptides for defence. A number of these gene-encoded peptides are linear with an amphipathic α-helical structure. These peptides can act alone or as synergistic complexes and have a broad antimicrobial activity.
Most antimicrobial peptides are membrane active, but their specific activity depends on peptide structure and membrane composition. In general, we test the selected peptides (and other membrane active compounds and extracts) against synthetic liposomes and various target cells to assess the activity parameter in our SAR studies. The antimicrobial peptide targets include erythrocytes, certain eukaryotic cell lines, different filamentous fungi, yeasts, Gram-positive and Gram-negative bacteria, as well as pathogenic and blood-borne microbes such as parasites causing malaria (Plasmodium falciparum) and African sleeping sickness (Trypanosoma brucei). Many of the pathogenic target organisms such Listeria monocytogenes, Candida albicans, and Pseudomonas spp have shown resistance towards conventional antibiotic, in particular because they tend to form resistant biofilms. As resistance towards antimicrobial peptides are rare, the prevention and eradication of biofilms by antimicrobial peptides is one of our focus areas.
To gain insight into biological factors governing activity and mode of action and to determine the SAR structural parameters, we study the solution behaviour/structure of selected antimicrobial compounds (natural isolates and synthetic analogues) in the presence/absence of biometals, lipid membranes, hydrophobic matrixes (C18 and C8), formulations and other antimicrobial peptides (co-produced peptides or peptides from competitors).
Apart from various techniques to purify and measure bio-activity of the synthetic peptides, techniques such as electron microscopy, atomic force microscopy, electrospray mass spectrometry, circular dichroism, nuclear magnetic resonance spectrometry, infra-red and fluorescence spectroscopy and high performance liquid chromatography are being utilised the selected antimicrobial compounds. We also utilise a number of cell biology techniques to determine the mode of action and alternative intracellular targets of selected antimicrobial peptides.
Application of research
One of the major long term goals of our current research is to develop natural biocide formulations from one or more of the peptide compounds in our libraries with promising antifungal and antibacterial activity. In particular, our the focus is currently on the development of antibiotic peptides produced by soil organisms as natural fungicides and antimicrobials for application in food preservation, agriculture and the medical field.
Peptide synthesis, production and purification service
The laboratory housing the BIOPEP Peptide Group also has a peptide synthesis, production and purification unit that provides a service to research collaborators and industry. BIOPEP is currently the only group in South Africa producing synthetic peptides for industry. For more details contact me.
Nieuwoudt M, Lombard N, Rautenbach M* (2014) Optimised purification and characterisation of lipid transfer protein 1 (LTP1) and its lipid-bound isoform LTP1b from barley malt. Food Chemistry 157, 559–567, DOI: 10.1016/j.foodchem.2014.02.076
Munyuki G., Jackson GE, Venter GA, Kövér KE, Szilágyi L, Rautenbach M, Spathelf BM, Bhattacharya B and Van der Spoel D* (2013) b-Sheet structures and dimer models of two major tyrocidines, antimicrobial peptides from Bacillus aneurinolyticus, Biochemistry, 44, 7798–7806, DOI: 10.1021/bi401363m
Troskie AM, Vlok NM, Rautenbach M* (2012). A novel 96-well gel-based assay for determining antifungal activity against filamentous fungi. Journal of Microbiological Methods, 91, 551–558; DOI: 10.1016/j.mimet.2012.09.025
Spathelf BM, Rautenbach M* (2009) Anti-listerial activity and structure–activity relationships of the six major tyrocidines, cyclic decapeptides from Bacillus aneurinolyticus, Bioorganic & Medicinal Chemistry 17, 5541–5548; DOI: 10.1016/j.bmc.2009.06.029
Rautenbach M, Vlok NM, Stander M, Hoppe HC* (2007) Inhibition of malaria parasite blood stages by tyrocidines, membrane-active cyclic peptide antibiotics from Bacillus brevis, BBA Biomembranes, 1768, 1488-1497 ; DOI: 10.1016/j.bbamem.2007.01.015
Rautenbach M*, Gerstner GD, Vlok NM, Kulenkampff J, Westerhoff HV (2006) Analyses of dose-response curves, to compare the antimicrobial activity of model cationic a-helical peptides, highlights the necessity for a minimum of two activity parameters, Analytical Biochemistry 350, 81-90; DOI: 10.1016/j.ab.2005.11.027
Meincken M, Holroyd D L, Rautenbach M* (2005) An AFM study of the effect of antimicrobial peptides on the outer membrane of Escherichia coli, Antimicrobial Agents and chemotherapy, 49(10), 4085-4092; DOI: 10.1128/AAC.49.10.4085-4092.2005
Vadyvaloo V, Arous S, Gravesen A, Héchard Y, Chauhan-Haubrock R, Hastings JW, Rautenbach M* (2004) Cell-surface alterations in class IIa bacteriocin resistant Listeria monocytogenes strains. Microbiology-SGM, 150, 3025-3033; DOI: 10.1099/mic.0.27059-0
Vadyvaloo V, Hastings JW, Van der Merwe MJ, Rautenbach M* (2002) Membranes of class IIa bacteriocin-resistant Listeria monocytogenes contain increased levels of desaturated and short-acyl-chain phospatidylgycerols. Applied and Environmental Microbiology, 68, 5223-5230; DOI: 10.1128/AEM.68.11.5223-5230.2002
Du Toit EA, Rautenbach M* (2000) A sensitive standardised micro-gel well diffusion assay for the determination of antimicrobial activity. Journal of Microbiological Methods, 42, 159-165; DOI: 10.1016/S0167-7012(00)00184-6
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