Marina Rautenbach

Stellenbosch University | SUN · Department of Biochemistry

The structures and stability of sodiated species of 8-Beta, a linear lipopeptide analog (beta-aminotetradecanoyl-NYNQPNS) of the antifungal peptide iturin A2, were evaluated by electrospray ionization mass spectrometry (ESI-MS). Association of the lipopeptide, 8-Beta, with sodium afforded protection from fragmentation at high cone voltages and incr...

Electrospray mass spectrometry was employed as a tool in this first study on the molecular interaction between the alkali metal ions and antifungal lipopeptide iturin A, and some analogues. Cationisation by sodium and signal intensity of lipopeptide species depended on sodium concentration, but was independent of sample solvent, carrier solvent pol...

Antibiotic production as defense mechanism is a characteristic of a wide variety of organisms. In natural evolutionary adaptation cellular events such as sporulation, biofilm formation and resistance to antibiotics enable some microorganisms to survive environmental and antibiotic stress conditions. The two antimicrobial cyclic peptides in this stu...

We report on the structure of Gramicidin S (GS) in a model membrane mimetic environment represented by the amphipathic solvent 1-octanol using one-dimensional (1D) and two-dimensional (2D) IR spectroscopy. To explore potential structural changes of GS, we also performed a series of spectroscopic measurements at differing temperatures. By analyzing...

It was previously observed that the lipopeptide surfactants in surfactin (Srf) have an antagonistic action towards the highly potent antimicrobial cyclodecapeptide, gramicidin S (GS). This study reports on some of the molecular aspects of the antagonism as investigated through complementary electrospray ionization mass spectrometry techniques. We w...

Secondary metabolic profiling, using UPLC-MSE and molecular networking, revealed the secondary metabolites produced by Serratia marcescens NP10. The NP10 strain co-produced cyclic and open-ring stephensiolides (i.e., fatty acyl chain linked to Thr–Ser–Ser–Ile/Leu–Ile/Leu/Val) and glucosamine derivatives (i.e., fatty acyl chain linked to Val–glucose...

The ever-increasing global threat of common infections developing resistance to current therapeutics is rapidly accelerating the onset of a primitive post-antibiotic era in medicine. The prevention of further antimicrobial resistance development is unlikely due to the continued misuse of antibiotics, augmented by the lack of discovery of novel anti...

Tryptocidine C (TpcC), a Trp-rich cyclodecapeptide is a minor constituent in the antibiotic tyrothricin complex from Brevibacillus parabrevis. TpcC possesses a high tendency to oligomerise in aqueous solutions and dried TpcC forms distinct self-assembled nanoparticles. High-resolution scanning electron microscopy revealed the influence of different...

Previous research found that the six major cyclodecapeptides from the tyrothricin complex, produced by Brevibacillus parabrevis, showed potent activity against chloroquine sensitive (CQS) Plasmodium falciparum. The identity of the aromatic residues in the aromatic dipeptide unit in cyclo-(D-Phe1-Pro2-(Phe3/Trp3)-D-Phe4/D-Trp4)-Asn5-Gln6-(Tyr7/Phe7/...

A metabolomics/peptidomics and genomics approach, using UPLC-MSE, molecular networking, and genome mining, was used to describe the serrawettin W2 lipopeptide family produced by Serratia marcescens NP2. Seven known serrawettin W2 analogues were structurally elucidated along with 17 new analogues, which varied based on the first (fatty acyl length o...

Modified antimicrobial and antifouling materials and surfaces can be used to limit the propagation of microorganisms on various surfaces and minimise the occurrence of infection, transfer, and spoilage. Increased demand for ‘green’ solutions for material treatment has pushed the focus towards to naturally produced antimicrobials. Tyrocidines, cyclo...

Surface colonization by microorganisms, combined with the rise in antibiotic resistance, is the main cause of production failures in various industries. Self-sterilising materials are deemed the best prevention of surface colonization. However, current screening methods for these sterilising materials are laborious and time-consuming. The disk diff...

Candida species are highly adaptable to environmental changes with their phenotypic flexibility allowing for the evasion of most host defence mechanisms. Moreover, increasing resistance of human pathogenic Candida strains has been reported against all four classes of available antifungal drugs, which highlights the need for combinational therapies....

An integrated approach that combines reverse-phase high-performance liquid chromatography (RP-HPLC), electrospray ionization mass spectrometry, untargeted ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS E) and molecular networking (using the Global Natural Products Social molecular network platform) was used to...

Species from the genus Xenorhabdus, endosymbiotic bacteria of Steinernema nematodes, produce several antibacterial and antifungal compounds, some of which are anti-parasitic. In this study, we report on the effect growth conditions have on the production of antimicrobial compounds produced by Xenorhabdus khoisanae J194. The strain was cultured in a...

Tryptocidine C (TpcC, cyclo[D-Phe1-Pro2-Trp3-D-Trp4-Asn5-Gln6-Trp7-Val8-Orn9-Leu10]) is a broad-spectrum antimicrobial peptide in the tyrothricin complex produced by a soil bacterium, Brevibacillus parabrevis. Electrospray mass spectrometric studies reveal the oligomerisation of TpcC into dimers and higher oligomers, analogous to tyrocidine C (TrcC...

The concepts of polymer−peptide conjugation and self-assembly were applied to antimicrobial peptides (AMPs) in the development of a targeted antimalaria drug delivery construct. This study describes the synthesis of α-acetal, ω-xanthate hetero-telechelic poly(N-vinylpyrrolidone) (PVP) via reversible addition− fragmentation chain transfer (RAFT)-med...

The tyrocidines and analogues are cationic cyclodecapeptides [cyclo (D-Phe1-L-Pro2-L-(Phe3/Trp3)-D-(Phe4/Trp4)-L-Asn5-L-Gln6-L-(Tyr7/Phe7/Trp7)-L-Val8-L-(Orn9/Lys9)-L-Leu10], produced together with the neutral linear pentadecapeptide gramicidins, in the antibiotic tyrothricin complex by Brevibacillus parabrevis. Despite discovery 80 years ago, it w...

The authors would like to correct the errors in the publication of the original article.

Abstract A better knowledge of the SARS-CoV-2 virus and its underlying pathobiology is accumulating every day. Of huge importance now is to provide a fast, cost effective, safe, and immediately available pharmaceutical solution to curb the rapid global spread of SARS-CoV-2. This Opinion discusses the demands for such an ideal drug and taking into a...

Bacteria isolated from different segments of the gastro-intestinal tract (GIT) of healthy free-range broilers were screened for probiotic properties. Six strains were selected and identified as Lactobacillus gallinarum, Lactobacillus johnsonii, Lactobacillus salivarius, Lactobacillus crispatus, Enterococcus faecalis and Bacillus amyloliquefaciens b...

Aims: A mathematical model of the non-ribosomal synthesis of tyrocidines and analogues by Brevibacillus parabrevis was constructed using a competitive binding mechanism (CBM) for the incorporation of the three variable aromatic amino acid (Aaa) residues in their sequence. These antimicrobial peptides have a conserved structure (D-Phe1 -Pro2 -Aaa3...

Background: Xenorhabdus spp. live in close symbiosis with nematodes of the Steinernema genus. Steinernema nematodes infect an insect larva and release their symbionts into the haemocoel of the insect. Once released into the haemocoel, the bacteria produce bioactive compounds to create a semi-exclusive environment by inhibiting the growth of bacter...

Tyrocidines are a family of cyclic decapeptides produced by the soil bacterium, Brevibacillus parabrevis. These antibiotic peptides can be used to prevent infections in agriculture and food industry but also to prepare antimicrobial lozenges, creams, and dressings for medical applications. It has been observed that the tyrocidines interact with sac...

Cyclic β-sheet decapeptides from the tyrocidine group and the homologous gramicidin S were the first commercially used antibiotics, yet it remains unclear exactly how they kill bacteria. We investigated their mode of action using a bacterial cytological profiling approach. Tyrocidines form defined ion-conducting pores, induce lipid phase separation...

Tyrothricin is a peptide complex containing the linear gramicidins and cyclic tyrocidines. The tyrocidines have potent activity against fungal plant pathogens. As these peptides have possible agricultural applications, their toxicity was evaluated toward honey bee adults and larvae. Tyrothricin formulated in sucrose was non-toxic to caged adult hon...

Biosurfactants are unique secondary metabolites, synthesised non-ribosomally by certain bacteria, fungi and yeast, with their most promising applications as antimicrobial agents and surfactants in the medical and food industries. Naturally produced glycolipids and lipopeptides are found as a mixture of congeners, which increases their antimicrobial...

The quantitative and qualitative effect of water immiscible and miscible carbon-rich substrates on the production of biosurfactants, surfactin and rhamnolipids, by Bacillus amyloliquefaciens ST34 and Pseudomonas aeruginosa ST5, respectively, was analysed. A small-scale high throughput 96 deep-well micro-culture method was utilised to cultivate the...

The tyrocidines are basic, cyclic decapeptides (cyclo(D-Phe1-Pro2-X3-x4-Asn5-Gln6-X7-Val8-X9-Leu10) with antifungal, -malarial and -bacterial activity. Previously 28 tyrocidines and analogues were identified in culture extracts from Brevibacilus parabrevis. Tyrocidine variability is due to Phe, Trp and Tyr substitutions at positions 3, 4 and 7, and...

Many industries experience great losses due to persistent bacterial and fungal infections, most of which are biofilm related. Since the treatment of biofilms is problematic, prevention of microorganism colonisation to the surface can be done by modifying to solid surfaces and materials by covalent coupling, coating or absorption of antimicrobial ag...

The tyrocidines and analogues are cyclic decapeptides produced by Brevibacillus parabrevis with a conserved sequence of cyclo(D-Phe1-Pro2-X3-x4-Asn5-Gln6-X7-Val8-X9-Leu10) with Trp3,4/Phe3,4 in the aromatic dipeptide unit, Lys9/Orn9 as their cationic residue and Tyr (tyrocidines), Trp (tryptocidines) or Phe (phenicidines) in position 7. Previous st...

The tyrocidines and their analogues (Trcs) are a group of cyclodecapeptides [cyclo(D-Phe1-L-Pro2-L-(Phe3/Trp3)-D-(Phe4/Trp4)-L-Asn5-L-Gln6-L-(Tyr7/Phe7/Trp7)-L-Val8-L-Orn9-L-Leu10] produced by the soil bacterium Brevibacillus parabrevis. These cyclodecapeptides have shown potent antimicrobial activity toward a broad range of pathogens including Gra...

Most antifungal peptides (AFPs), if not all, have membrane activity, while some also have alternative targets. Fungal membranes share many characteristics with mammalian membranes with only a few differences, such as differences in sphingolipids, phosphatidylinositol (PI) content and the main sterol is ergosterol. Fungal membranes are also more neg...

Key policy messages • Sensitising the agricultural sector and the public to the possibility of natural alternatives in bio-control is crucial, although changing dogmatic perspectives will not be easy. Education on aspects of the natural production of food needs to start as early as secondary school and must preferably be included in tertiary/highe...

Agriculture and many other industries experience great losses due to persistent bacterial and fungal infections. Persistent infections are attributed to antibiotic or biocide resistance, mostly because of the formation of biofilms. Since the treatment of biofilms are problematic, prevention of microorganism colonization to the surface can be done b...

Tyrocidines were coupled via a trigger sensitive linker to hydrophylic bio-compatible polymer and allowed to self-assemble into nano-particles. In this form the tyrocidines can be used to selectively treat malaria parasite infected red blood cells and may be especially important in treating strains resistant to traditional drugs. The preparation is...

The six major tyrocidines (Trcs), cyclodecapeptides from Bacillus aneurinolyticus, were previously shown to have potent nanomolar activity against the malaria parasite Plasmodium falciparum 3D7, with the most hydrophobic peptide tyrocidine A (TrcA, VOLfPFfNQY) being the most active (Rautenbach et al., 2007, BBA Biomembranes, 1768, 1488–1497). Activ...

The enzymes in the Embden-Meyerhof-Parnas pathway of Plasmodium falciparum trophozoites were kinetically characterised and their integrated activities analysed in a mathematical model. For validation of the model we compared model predictions for steady state fluxes and metabolite concentrations of the hexose phosphates with experimental values for...

In beer brewing, brewers worldwide strive to obtain product consistency in terms of flavour, colour and foam. Important proteins contributing to beer foam are lipid transfer proteins (LTPs), in particular LTP1 and its lipid-bound isoform LTP1b, which are known to transport lipids in vivo and prevent lipids from destabilising the beer foam. LTP1 and...

In the 1950’s the transmission of malaria parasite, in particular Plasmodium falciparum, was successfully controlled using the antimalarial drug chloroquine (CQ) and the insecticide dichlorodiphenyltrichloroethane (DDT). However, in the late 1960’s resistance against CQ developed and since then resistance towards all the antimalarial drugs have als...

The tyrocidine production profile of two strains of Brevibacillus parabrevis, ATCC 10068 and ATCC 8185, was altered through the supplementation of the growth medium with two amino acids namely Phe and Trp. The tyrocidines and their analogues are cyclic decapeptides produced by B. parabrevis. The structure of the tyrocidines (fPX3x4NQX7VOL) may be a...

The tyrocidines, a complex of analogous cyclic decapeptides produced by Bacillus aneurinolyticus, exhibited noteworthy activity against a range of phytopathogenic fungi, including Fusarium verticillioides, F. solani and Botrytis cinerea. The activity of the tyrocidine peptide complex (Trc mixture) and purified tyrocidines exhibited minimum inhibiti...

Food shortages are augmented by pathogenic microorganisms, including fungi, which can lead to an annual crop loss of up to 16% and a further 50% post-harvest loss, especially in developing countries with limited infrastructure. The health risks, environmental impact and microbial resistance against conventional chemical fungicides necessitate the d...

This invention relates to compositions of natural peptide antibiotics containing or derived from the tyrocidines adsorbed to solid matrices to (1) prevent surface contamination and enable surface sterilization (2) prevent/treat biofilm formation and (3) possibly serve as vehicle to treat infected wounds (e.g. wound dressings). It was shown that tyr...

Tyrocidines are cationic cyclodecapeptides from Bacillus aneurinolyticus that are characterized by potent antibacterial and antimalarial activities. In this study, we show that various tyrocidines have significant activity against planktonic Candida albicans in the low-micromolar range. These tyrocidines also prevented C. albicans biofilm formation...

The tyrocidines, antimicrobial cyclic decapeptides from Bacillus aneurinolyticus have potent activity with drug/disinfectant potential, specifically against Listeria monocytogenes. The tyrocidine activity is dependent on an amphipathic balance. Structure-activity relationship (SAR) analysis combined with principal component analysis showed the best...

In keeping with recent efforts to generate compounds for antibiotic and microbicide development, we focused on the creation of non-natural organo-peptide hybrids of antimicrobial peptide amides (KLK(L)n KLK-NH2 ) derived from sapecin B and a self-assembling oligoglycine organo-peptide bolaphile containing an ω-amino fatty acid residue. The hybrid o...

The structures of two major tyrocidines, antibiotic peptides from Bacillus aneurinolyticus, in an aqueous environment were studied using nuclear magnetic resonance spectroscopy, restrained molecular dynamics (MD), circular dichroism, and mass spectrometry. TrcA and TrcC formed β-structures in an aqueous environment. Hydrophobic and hydrophilic resi...

Tryptophan and arginine-rich cyclic hexapeptides of the type cyclo-RRRWFW combine high antibacterial activity with rapid cell killing kinetics, but show low toxicity in human cell lines. The peptides fulfil the structural requirements for membrane interaction such as high amphipathicity and cationic charge, but membrane permeabilisation, which is t...

A group of non-ribosomally produced antimicrobial peptides, the tyrocidines from the tyrothricin complex, have potential as antimicrobial agents in both medicine and industry. Previous work by our group illustrated that the more polar tyrocidines rich in tryptophan residues in their structure were more active toward Gram-positive bacteria, while th...

ompositions containing one or more tyrocidines, tryptocidines, phenycidines and/or gramicidin S, or derivatives and analogues thereof, are described for controlling antimicrobial growth on plants, plant material or plant growth media, and methods for controlling or preventing the growth of microbial pathogens, and in particular fungal pathogens, on...

Cyclic R-,W-rich hexapeptides of the type cyclo(RRRWFW) combine high antibacterial activity with a rapid cell killing kinetics whilst no toxicity towards eukaryotic cells was detected [1,2]. The peptides fulfil the structural requirements for membrane interaction such as high amphipathicity and cationic charge. However, membrane permeabilisation wh...

In recent years the global rise in antibiotic resistance and environmental consciousness lead to a renewed fervour to find and develop novel antibiotics, including antifungals. However, the influence of the environment on antifungal activity is often disregarded and many in vitro assays may cause the activity of certain antifungals to be overestima...

Infection with the opportunistic pathogen Listeria monocytogenes may lead to listeriosis, a major public health concern.[1] Listeria is a food safety threat with an equally wide economic impact.[1] Reports of resistance development emphasize the need for new drugs and disinfectants with alternative mechanisms of action.[2] The tyrocidines (Trcs) ar...

We utilised a simple bidirectional (N→C and C→N) solid phase synthesis strategy entailing conventional solid phase peptide synthesis and fragment condensation with a water-soluble carbodiimide to synthesise a model anionic glycylglycine bolaamphiphile containing a suberic acid linker moiety, namely N,N'-suberoyldiglycylglycine. The synthetic subero...

In beer brewing, brewers across the globe strive to obtain product consistency. Quality determining factors includes product package, colour, clarity and flavour. Another crucial aspect of beer that demands consistence is beer foam. Probably the most important proteins/peptides contributing to beer foam are lipid transfer protein (LTP1) and protein...

The mode of action of short, nonhelical antimicrobial peptides is still not well understood. Here we show that these peptides interact with ATP and directly inhibit the actions of certain ATP-dependent enzymes, such as firefly luciferase, DnaK, and DNA polymerase. α-Helical and planar or circular antimicrobial peptides did not show such interaction...

Six major tyrocidines, purified from the antibiotic tyrothricin complex produced by Bacillus aneurinolyticus, showed significant lytic and growth inhibitory activity towards the gram+ bacteria, Micrococcus luteus and Listeria monocytogenes, but not against the gram- bacterium, Escherichia coli. The isolated natural tyrocidines were in particular mo...

Membrane active anti-yeast compounds, such as antimicrobial peptides and proteins, cause yeast membrane damage which is likely to affect yeast vitality and fermentation performance, parameters which are notoriously difficult to analyse. In this work the sensitivity of lager brewery yeast strains towards barley malt extracts with anti-yeast activity...

The brewing of beer involves two major biological systems, namely malted barley (malt) and yeast. Both malt and yeast show natural variation and assessing the impact of differing malts on yeast performance is important in the optimisation of the brewing process. Currently, the brewing industry uses well-established tests to assess malt quality, but...

Objective HYNIC (hydrazinonicotinamide) are one of the well known bifunctional chelates used to complex technetium-99m. Due to different reasons the labelling yield of HYNIC derivitised biological active moieties (BAM) varies and frequently purification of the labelled compound needs to be performed. One method to circumvent this problem is to prot...

Tyrothricin, a complex mixture of antibiotic peptides from Bacillus brevis, was reported in 1944 to have antimalarial activity rivalling that of quinine in chickens infected with Plasmodium gallinaceum. We have isolated the major components of tyrothricin, cyclic decapeptides collectively known as the tyrocidines, and tested them against the human...

(EN)Polyene macrolide compounds, analogues thereof and compositions containing polyene macrolides or analogues are described for use in treating malaria infections in humans and animals. Examples of polyene macrolide compounds are amphotericin B, nystatin A, natamycin (pimaricin), filipin, rimocidin, candidin and vacidin, and in particular, formula...

Microbial colonization of the barley plant tissue occurs in the field while the crop is growing. Accordingly, all barley grain/seed will have some microflora, although the amount and type of microorganisms may vary. Barley is one of the major raw materials used for brewing, and microflora on barley has long been associated with a number of quality...

The continuous increase in strains of the human malaria parasite Plasmodium falciparum resistant to most front-line antimalarial compounds is reason for grave clinical concern. The search for new drugs led us to investigate a number of membrane active polyene macrolide antibiotics, such as amphotericin B, nystatin, filipin and natamycin. The intera...

To assess and compare different model Leu-Lys-containing cationic alpha-helical peptides, their antimicrobial activities were tested against Escherichia coli as target organism over a broad peptide concentration range. The natural cationic alpha-helical peptides magainin 2 and PGLa and the cyclic cationic peptide gramicidin S were also tested betwe...

To assess and compare different model Leu-Lys-containing cationic a-helical peptides, their antimicrobial activities were tested against Escherichia coli as target organism over a broad peptide concentration range. The natural cationic a-helical peptides magainin 2 and PGLa and the cyclic cationic peptide gramicidin S were also tested between compa...

The influences of the antibacterial magainin 2 and PGLa from the African clawed frog (Xenopus laevis) and the hemolytic bee venom melittin on Escherichia coli as the target cell were studied by atomic force microscopy (AFM). Nanometer-scale images of the effects of the peptides on this gram-negative bacterium's cell envelope were obtained in situ w...

Strains of the food-borne pathogen Listeria monocytogenes, showing either intermediate or high-level resistance to class IIa bacteriocins, were investigated to determine characteristics that correlated with their sensitivity levels. Two intermediate and one highly resistant spontaneous mutant of L. monocytogenes B73, a highly resistant mutant of L....

High-level resistance to class IIa bacteriocins has been directly associated with the absent EIIAB(Man) (MptA) subunit of the mannose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) (EIIt(MAN)) in Listeria monocytogenes strains. Class IIa bacteriocin-resistant strains used in this study were a spontaneous resistant, L. monocy...

A major concern in the use of class IIa bacteriocins as food preservatives is the well-documented resistance development in target Listeria strains. We studied the relationship between leucocin A, a class IIa bacteriocin, and the composition of the major phospholipid, phosphatidylglycerol (PG), in membranes of both sensitive and resistant L. monocy...

We have developed a highly sensitive micro-gel well diffusion assay for the determination of antimicrobial activity. In essence, the normal radial diffusion type assay was adapted to perform it in a microtiter plate. We compared our micro-gel well diffusion assay to a radial diffusion assay and a microtiter broth dilution method, using gramicidin S...