Pathogenic Yeast Candida Albicans Research Articles

Comparison between Conventional Methods and Molecular Diagnosis for Candida albicans and Candida dubliniensis isolated from Cancer Patients Infected with Oral Candidiasis

Abstract Background: Two related pathogenic yeast species, Candida albicans and Candida dubliniensis share many phenotypic and microscopic diagnostic characteristics, in addition to the similarity in the characteristics of diagnosis. Objectives: The present study aimed to diagnose both yeast cells and compare them at the level of the percentage of similarities and differences according to the traditional methods and molecular approaches, which are considered more accurate and sensitive. Materials and Methods: The ability to form germ tubes was conducted for C. albicans and C. dubliniensis. The identification using biochemical tests, VITEK techniques, and molecular techniques was also conducted. Results: The results showed that both pathogenic yeast cells are similar in phenotypic and biochemical diagnosis, whereas the results of molecular diagnosis showed a difference between them, as well as the results of the drug sensitivity test, showed that the two types of yeast cells are sensitive to the antifungal drugs. The current study also showed the diagnosis of new isolates of the two species for the first time, which can be attributed to the occurrence of genetic mutations in them. Conclusion: Both types of pathogenic yeasts that were diagnosed in the current study are the important pathological types prevalent in cancer patients, especially in oral cavity infections, and they are similar to a large extent in terms of phenotypic and diagnostic characteristics.

Engineering Adhesion of the Probiotic Strain Escherichia coli Nissle to the Fungal Pathogen Candida albicans.

Engineering live biotherapeutic products against fungal pathogens such as Candida albicans has been suggested as a means to tackle the increasing threat of fungal infections and the development of resistance to classical antifungal treatments. One important challenge in the design of live therapeutics is to control their localization inside the human body. The specific binding capability to target organisms or tissues would greatly increase their effectiveness by increasing the local concentration of effector molecules at the site of infection. In this study, we utilized surface display of carbohydrate binding domains to enable the probiotic E. coli Nissle 1917 to adhere specifically to the pathogenic yeast Candida albicans. Binding was quantified using a newly developed method based on the automated analysis of microscopic images. In addition to a rationally selected chitin binding domain, a synthetic peptide of identical length but distinct sequence also conferred binding. Efficient binding was specific to fungal hyphae, the invasive form of C. albicans, while the yeast form, as well as abiotic cellulose and PET particles, was only weakly recognized.

Bio-efficacy of Essential Oil Extracted from Locally Available Orange (Citrus sinensis) Peels from Nepal

Essential oils from various plants are valued for their therapeutic, aromatic, antimicrobial, and antioxidant properties. The majority of them are employed in cleaning procedures, aromatherapy, stress reduction, food flavouring and preservation, and beauty products. The present investigation focuses on elucidating the chemical composition along with the antimicrobial and antioxidant properties of essential oil extracted from locally available orange (Citrus sinensis) peels, mainly exploring its bio-efficacy. The antibacterial property was studied against the gram-negative bacterium Escherichia coli and the gram-positive bacterium Bacillus subtilis. The analysis results revealed significant antimicrobial activity with zones of inhibition of 4 mm and 5.5 mm, respectively. The antifungal property was studied against the opportunistic pathogenic yeast Candida albicans, which showed positive activity, producing 4.5 mm of zone of inhibition. The antioxidant activity of the oil was determined using DPPH free radical scavenging assay, which showed an IC50 value of 1.3532 µL/mL. Qualitative phytochemical screening of the essential oil as determined using some standard colour-developing methods showed the presence of alkaloids, flavonoids, terpenoids, phenols, cardiac glycosides, and saponins. The above results were validated by FT-IR and GC/MS analysis. The FT-IR analysis revealed the presence of nitrogen-containing and oxygen-containing functional groups. The GC/MS analysis showed the presence of limonene, d-limonene, 1S-α-Pinene, 1R-α-Pinene, β-myrcene, linalool, α-humulene, α-terpineol, etc. These findings demonstrated that orange peels from Nepal that are readily available locally could be a source of compounds with antibacterial, antifungal, and antioxidant properties.

Właściwości i zastosowanie gruzińskiego naturalnego filipsytu

Oceanic and terrestrial sedimentary phillipsites make up very large reserves, but the use of this natural zeolite is not so wide comparing to clinoptilolite, and purpose of our study was to characterize the phillipsites of the Georgian deposits and highlight their possible application. It is shown that natural phillipsite can be used as a raw material for the synthesis of phase-pure zeolite NaX with Si/Al~1.5-1.7 in the form of octahedral crystallites with uniform micrometric (2-7 μm) dimensions, characterized by high specific surface area (590-770 m2/g) and volume of pores (0.58 cm3/g) including uniform zeolitic micropores and channels with an average diameter of 55 nm, which opens up the prospect of its use in catalysis. It has been established that natural phillipsite is a suitable carrier of bioactive metals: silver-, copper-, and zinc-containing micro-mesoporous materials have been prepared using ion-exchange reactions between zeolite and a salt of a transition metal; the products contain up to 235 mg/g of silver, 85 mg/g of copper, and 87 mg/g of zinc, and in the Kirby-Bauer disk-diffusion test show strong bacteriostatic activity against such microorganisms as gram-negative bacterium Escherichia coli, gram-positive bacteria Staphylococcus aureus and Bacillus subtilis, fungal pathogenic yeast Candida albicans and a fungus Aspergilus niger. The use of bactericidal materials obtained on the basis of natural phillipsite is possible both for water purification and disinfection, and as fillers in the production of polymeric materials, paper and cardboard.

The zinc cluster transcription factor Znc1 regulates Rta3-dependent miltefosine resistance in Candida albicans.

Transcription factors are central regulators of gene expression, and knowledge about which transcription factor regulates specific genes in response to a certain signal is important to understand the behavior of organisms. In the pathogenic yeast Candida albicans, the RTA3 gene is required for wild-type tolerance of miltefosine, an antiparasitic drug that is considered for treatment of invasive candidiasis. Activated forms of the transcription factors Tac1 and Znc1 cause constitutive overexpression of RTA3 and thereby increased miltefosine resistance, but only Tac1 mediates upregulation of RTA3 in response to the known inducer fluphenazine. RTA3 expression is also induced by miltefosine, and we found that this response depends on Znc1, whereas Tac1 is dispensable. Consequently, znc1Δ mutants were hypersensitive to miltefosine, whereas tac1Δ mutants showed wild-type tolerance. These findings demonstrate that Znc1 is the key regulator of RTA3 expression in response to miltefosine that is important for wild-type miltefosine tolerance.

Modifying of physical, biodegradation, drug delivery characteristics of bioactive borophosphate glass by addition of molybdenum

In this study, high valence MoO3 was added to bioactive glass based on (50-x) P2O5 - 20 B2O3 – 20 CaO - 10 Na2O (x = 0, 5, 10–15 mol. %; the corresponding samples encoded as 0-Mo, 5-Mo, 10-Mo, and 15-Mo) to modify its physical, biodegradation, drug delivery properties. The glasses were prepared via melt-quenching process. The obtained glasses were analyzed by XRD, FTIR, SEM, Raman, and zeta potential (-42, - 31.8, - 34.5, and - 26.4 mV for 0-Mo, 5-Mo, 10-Mo, and 15-Mo, respectively). The in vitro bioactivity and biodegradation were examined in the simulated body fluid (SBF). The glasses were checked for ability for drug delivery by using ciprofloxacin (CIP) antibiotic as a drug model to attain an anticipated therapeutic response to avoid infections, and the drug release kinetic was studied by fitting the release data with Higuchi and Hixon-Crowell models. Finally, the antibacterial activity of the glasses conjugated with drug and drug-free glasses was tested against gram positive bacteria (Streptococcus aureus), gram negative bacteria (Escherchia coli) and Pathogenic yeast (Candida albicans). The results showed that the glasses were characterized by amorphous structure, and it showed a good bioactivity after immersion in SBF. Moreover, the results presented that addition of molybdenum increased the degradation rate of the glasses and affected their surface charge to less negative. In addition, it increased the drug loading efficiency and drug release rate, where 11.2 %, 56.9 %, 75.4 %, and 83.6 % of the drug released from 0-Mo, 5-Mo, 10-Mo, and 15-Mo, respectively, at the end of incubation time. The drug release occurred by combined diffusion and dissolution mechanism. Finally, antibacterial activity showed that drug-free glasses possessed antibacterial activity against the bacterial, meanwhile the antibacterial activity increased by loading CIP on the glass particles. In conclusion, different physical properties, as well as biodegradation and drug release can be tailored by addition of molybdenum. On the other hand, the prepared glasses are expected to be used successfully as multifunctional bone grafting materials.

Use of the Fluorescent Dye Thioflavin T to Track Amyloid Structures in the Pathogenic Yeast Candida albicans.

The human pathogenic yeast Candida albicans can attach to epithelial cells or indwelling medical devices to form biofilms. These microbial communities are highly problematic in the clinic as they reduce both sensitivity to antifungal drugs and detection of fungi by the immune system. Amyloid structures are highly organized quaternary structures that play a critical role in biofilm establishment by allowing fungal cells to adhere to each other. Thus, fungal amyloids are exciting targets to develop new antifungal strategies. Thioflavin T is a specific fluorescent dye widely used to study amyloid properties of target proteins in vitro (spectrophotometry) and in vivo (epifluorescence/confocal microscopy). Notably, thioflavin T has been used to demonstrate the ability of Als5, a C. albicans adhesin, to form an amyloid fiber upon adhesion. We have developed a pipeline that allows us to study amyloid properties of target proteins using thioflavin T staining in vitro and in vivo, as well as in intact fungal biofilms. In brief, we used thioflavin T to sequentially stain (i) amyloid peptides, (ii) recombinant proteins, (iii) fungal cells treated or not with amyloid peptides, (iv) fungal amyloids enriched by cell fractionation, and (v) intact biofilms of C. albicans. Contrary to other methods, our pipeline gives a complete picture of the amyloid behavior of target proteins, from in vitro analysis to intact fungal biofilms. Using this pipeline will allow an assessment of the relevance of the in vitro results in cells and the impact of amyloids on the development and/or maintenance of fungal biofilm. Key features • Study of amyloid properties of fungal proteins. • Visualization of the subcellular localization of fungal amyloid material using epifluorescence or confocal microscopy. • Unraveling of the amyloid properties of target proteins and their physiological meaning for biofilm formation. • Observation of the presence of amyloid structures with live-cell imaging on intact fungal biofilm using confocal microscopy.

Multiple phosphorylation sites regulate the activity of the repressor Mig1 in Candida albicans.

The SNF1 protein kinase signaling pathway, which is highly conserved in eukaryotic cells, is important for metabolic adaptations in the pathogenic yeast Candida albicans. However, so far, it has remained elusive how SNF1 controls the activity of one of its main effectors, the repressor protein Mig1 that inhibits the expression of genes required for the utilization of alternative carbon sources when glucose is available. In this study, we have identified multiple phosphorylation sites in Mig1 that contribute to its inactivation. Mutation of these sites strongly increased Mig1 repressor activity in the absence of SNF1, but SNF1 could still sufficiently inhibit the hyperactive Mig1 to enable growth on alternative carbon sources. These findings reveal features of Mig1 that are important for controlling its repressor activity. Furthermore, they demonstrate that both SNF1 and additional protein kinases regulate Mig1 in this pathogenic yeast.

The role of the Mediator complex in fungal pathogenesis and response to antifungal agents.

Mediator is a complex of polypeptides that plays a central role in the recruitment of RNA polymerase II to promoters and subsequent transcriptional activation in eukaryotic organisms. Studies have now shown that Mediator has a role in regulating expression of genes implicated in virulence and antifungal drug resistance in pathogenic fungi. The roles of specific Mediator subunits have been investigated in several species of pathogenic fungi, particularly in the most pathogenic yeast Candida albicans. Uniquely, pathogenic yeast also present several interesting examples of divergence in Mediator structure and function, most notably in C. glabrata, which possesses two orthologues of Med15, and in C. albicans, which has a massively expanded family of Med2 orthologues known as the TLO gene family. This review highlights specific examples of recent progress in characterizing the role of Mediator in pathogenic fungi.

The Ypk1 protein kinase signaling pathway is rewired and not essential for viability in Candida albicans.

Protein kinases are central components of almost all signaling pathways that control cellular activities. In the model organism Saccharomyces cerevisiae, the paralogous protein kinases Ypk1 and Ypk2, which control membrane lipid homeostasis, are essential for viability, and previous studies strongly indicated that this is also the case for their single ortholog Ypk1 in the pathogenic yeast Candida albicans. Here, using FLP-mediated inducible gene deletion, we reveal that C. albicans ypk1Δ mutants are viable but slow-growing, explaining prior failures to obtain null mutants. Phenotypic analyses of the mutants showed that the functions of Ypk1 in regulating sphingolipid biosynthesis and cell membrane lipid asymmetry are conserved, but the consequences of YPK1 deletion are milder than in S. cerevisiae. Mutational studies demonstrated that the highly conserved PDK1 phosphorylation site T548 in its activation loop is essential for Ypk1 function, whereas the TORC2 phosphorylation sites S687 and T705 at the C-terminus are important for Ypk1-dependent resistance to membrane stress. Unexpectedly, Pkh1, the single C. albicans orthologue of Pkh1/Pkh2, which mediate Ypk1 phosphorylation at the PDK1 site in S. cerevisiae, was not required for normal growth of C. albicans under nonstressed conditions, and Ypk1 phosphorylation at T548 was only slightly reduced in pkh1Δ mutants. We found that another protein kinase, Pkh3, whose ortholog in S. cerevisiae cannot substitute Pkh1/2, acts redundantly with Pkh1 to activate Ypk1 in C. albicans. No phenotypic effects were observed in cells lacking Pkh3 alone, but pkh1Δ pkh3Δ double mutants had a severe growth defect and Ypk1 phosphorylation at T548 was completely abolished. These results establish that Ypk1 is not essential for viability in C. albicans and that, despite its generally conserved function, the Ypk1 signaling pathway is rewired in this pathogenic yeast and includes a novel upstream kinase to activate Ypk1 by phosphorylation at the PDK1 site.

Synthesis, characterisation, and solution behaviour of Ag(I) bis(phenanthroline-oxazine) complexes and the evaluation of their biological activity against the pathogenic yeast Candida albicans

Three Ag(I) bis(phenanthroline-oxazine) complexes with varying lipophilicity were synthesised and characterised. The solution stoichiometry of 1:2 Ag(I):ligand was determined for each complex by the continuous variation Job’s plot method using NMR spectroscopy. NMR studies were also carried out to investigate the fluxional behaviour of the Ag(I) complexes in solution. The biological activity of the silver(I) complexes and the corresponding ligands towards a clinical strain of Candida albicans MEN was studied using broth microdilution assays. Testing showed the choice of media and the duration of incubation were key determinants of the inhibitory behaviour towards Candida albicans, however, the difference between freshly prepared and pre-prepared solutions was insignificant in minimal media. The activity of the metal-free ligands correlated with the length of the alkyl chain. In minimal media, the methyl ester phenanthroline-oxazine ligand was effective only at 60 μM, limiting growth to 67% of the control, while a 60 μM dose of the propyl ester analogue limited fungal growth at < 20% of the control. MIC50 and MIC80 values for the propyl and hexyl ester analogues were calculated to be 45 and 59 µM (propyl), and 18 and 45 µM (hexyl). Moreover, in a study of activity as a function of time it was observed that the hexyl ester ligand maintained its activity for longer than the methyl and propyl analogues; after 48 h a 60 μM dose held fungal growth at 24% of that of the control. Complexation to Ag(I) was much more effective in enhancing biological activity of the ligands than was increasing the ester chain length. Significantly no difference in activity between the three silver(I) complexes was observed under the experimental conditions. All three complexes were substantially more active than their parent ligands against Candida albicans and AgClO4 and the three silver(I) bis(phen-oxazine) complexes have MIC80 values of < 15 μM. The ability of the silver(I) complexes to hold fungal growth at about 20% of the control even after 48 h incubation at low dosages (15 μM) showcases their superiority over the simple silver(I) perchlorate salt, which ceased to be effective at dosages below 60 μM at the extended time point.

Acetate modulates the inhibitory effect of Lactobacillus gasseri against the pathogenic yeasts Candida albicans and Candida glabrata

The exploration of the interference prompted by commensal bacteria over fungal pathogens is an interesting alternative to develop new therapies. In this work we scrutinized how the presence of the poorly studied vaginal species Lactobacillus gasseri affects relevant pathophysiological traits of Candida albicans and Candida glabrata. L. gasseri was found to form mixed biofilms with C. albicans and C. glabrata resulting in pronounced death of the yeast cells, while bacterial viability was not affected. Reduced viability of the two yeasts was also observed upon co-cultivation with L. gasseri under planktonic conditions. Either in planktonic cultures or in biofilms, the anti-Candida effect of L. gasseri was augmented by acetate in a concentration-dependent manner. During planktonic co-cultivation the two Candida species counteracted the acidification prompted by L. gasseri thus impacting the balance between dissociated and undissociated organic acids. This feature couldn't be phenocopied in single-cultures of L. gasseri resulting in a broth enriched in acetic acid, while in the co-culture the non-toxic acetate prevailed. Altogether the results herein described advance the design of new anti-Candida therapies based on probiotics, in particular, those based on vaginal lactobacilli species, helping to reduce the significant burden that infections caused by Candida have today in human health.

In vitro Antioxidant, Enzyme Inhibitory and Antimicrobial Evaluation of Sideritis caesarea H. Duman, Aytaç &amp; Başer Extracts

Sideritis caesarea H. Duman, Aytaç &amp; Başer of the family Lamiaceae is an endemic plant with different ethnobotanical uses in Anatolia. In this present study, the antioxidant and biological activity potential of different S caesarea extracts and purified compounds were evaluated in vitro using DPPH•, CUPRAC, and ABTS• methods. In addition, their urease and chymotrypsin enzyme inhibitory activities, antimicrobial potential, and total phenol and flavonoid contents were determined. The experimental results showed that the two isolated flavonoids {4′- O-methylhypolaetin-7- O-[6″′- O-acetyl- β-D-allopyranosyl-(1→2)]-6″- O-acetyl- β-D-glucopyranoside, and isoscutellarein-7- O-[6″′- O-acetyl- β-D-allopyranosyl-(1→2)]-6″- O-acetyl- β-D-glucopyranoside}, as well as their fractions, except the n-hexane and water residue, showed remarkable antioxidant activity. Interestingly, the ethyl acetate and water residue fractions inhibited the urease enzyme activity by 49.6% and 49.1%, respectively; while the n-hexane and dichloromethane fractions attracted attention with their relative high chymotrypsin inhibitory activity of 85.8%, and 82.4%, respectively. When evaluated for their in vitro antimicrobial potential, including Helicobacter pylori, only Bacillus subtilis was susceptible to the n-butanol fraction at 1 mg/mL, while all of the studied samples showed activity against the human pathogenic yeast Candida albicans with the range of 0.25 to 1 mg/mL minimum inhibitory concentrations. The initial antioxidant activity, enzyme inhibitions, and antimicrobial results of S caesarea extracts and compounds suggest the further potential for in vivo evaluations.

Antimicrobial Activity of Green Synthesized Silver Nanoparticles Using Waste Leaves of Hyphaene thebaica (Doum Palm).

Silver nanoparticles (AgNPs) were biosynthesized for the first time from waste leaves extract of local doum palms in Tabuk, Saudi Arabia. The transmission electron microscope (TEM) revealed a spherical shape with a particle size from 18 to 33 nm. The d-spacing is about 2.6 Å, which confirms a face-centered cubic crystalline building. The biosynthesized AgNPs were evaluated as an antimicrobial agent against several pathogenic bacteria, including Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, and Pseudomonas aeruginosa ATCC 27853. The highest action was exerted against S. aureus ATCC 29213 (MIC = 1.5 µg/mL). Interestingly, AgNPs also showed anticandidal activity against the pathogenic yeasts Candida albicans ATCC 14053 (MIC = 24 µg/mL) and Candida tropicalis ATCC 13803 (MIC = 96 µg/mL). Scanning electron microscope (SEM) revealed deep morphological changes in Candida spp. due to the treatment of the AgNPs. Scarce pseudohyphae, perforation, exterior roughness, irregularly shaped cells, and production of protective exopolysaccharide (EPS) were the main features. In conclusion, the process of biosynthesis of AgNPs from the aqueous leaf extract of Hyphaene thebaica is environmentally compatible and induces the biosynthesis of tiny AgNPs that could be a promising candidate in biomedical applications, including antimicrobials against some pathogenic bacteria and yeasts.

Volatile Compounds, Fatty Acids Constituents, and Antimicrobial Activity of Cultured Spirulina (Arthrospira fusiformis) Isolated from Lake Mariout in Egypt.

In this study, Arthrospira fusiformis previously isolated from Lake Mariout (Alexandria, Egypt) was cultivated in the laboratory using a medium for pharmaceutical grade Arthrospira, named as Amara and Steinbüchel medium. Hot water extract of the Egyptian Spirulina was prepared by autoclaving dried biomass in distilled water at 121°C for 15 min. This algal water extract was analyzed by GC-MS to evaluate its volatile compounds and fatty acids composition. The antimicrobial activity of phycobiliprotein extract from Arthrospira fusiformis using phosphate buffer was evaluated against thirteen microbial strains (two Gram-positive bacteria, eight Gram-negative bacteria, one yeast, and two filamentous fungi). The major components of fatty acids in the hot extract of Egyptian A. fusiformis were hexadecanoic acid (palmitic acid, 55.19%) and octadecanoic acid (stearic acid, 27.14%). The main constituents of its volatile compounds were acetic acid (43.33%) and oxalic acid (47.98%). The most potent antimicrobial effect of phycobiliprotein extract was obtained against two Gram-negative bacteria Salmonella typhi and Proteus vulgaris, filamentous fungus Aspergillus niger, and the pathogenic yeast Candida albicans (all of which showed MIC values of 58.1 μg/ml). Escherichia coli and Salmonella typhimurium come second in their susceptibility to the phycobiliprotein extract from Arthrospira fusiformis and Serratia marcescens and Aspergillus flavus are the least in susceptibility, with MIC values of 116.2 and 232.5 μg/ml, respectively, while phycobiliprotein extract has no antibacterial effect on methicillin-resistant as well as susceptible Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Shigella sonnei. These findings confirmed the nutritional value of Egyptian A. fusiformis isolated from Lake Mariout and suggest the potential use of this strain as an ingredient in the cooking of some foods to increase the level of stearic acid and palmitic acid. Moreover, its effective antibacterial activities against some important and highly resistant to antibiotics bacterial pathogens in addition to its antifungal effects recommend the therapeutic use of its biomass.

Escherichia coli, but Not Staphylococcus aureus, Functions as a Chelating Agent That Exhibits Antifungal Activity against the Pathogenic Yeast Candida albicans.

Humans are colonized by diverse populations of microbes. Infections by Candida albicans, an opportunistic fungal pathogen, are a result of imbalances in the gut microbial ecosystem and are due to the suppressed immunity of the host. Here, we explored the potential effects of the polymicrobial interactions of C. albicans with Staphylococcus aureus, a Gram-positive bacterium, and Escherichia coli, a Gram-negative bacterium, in dual and triple in vitro culture systems on their respective growth, morphology, and biofilms. We found that S. aureus promoted the fungal growth and hyphal transition of C. albicans through cell-to-cell contacts; contrarily, both the cell and cell-free culture filtrate of E. coli inhibited fungal growth. A yet to be identified secretory metabolite of E. coli functionally mimicked EDTA and EGTA to exhibit antifungal activity. These findings suggested that E. coli, but not S. aureus, functions as a chelating agent and that E. coli plays a dominant role in regulating excessive growth and, potentially, the commensalism of C. albicans. Using animal models of systemic candidiasis, we found that the E. coli cell-free filtrate suppressed the virulence of C. albicans. In general, this study unraveled a significant antimicrobial activity and a potential role in the nutritional immunity of E. coli, and further determining the underlying processes behind the E. coli-C. albicans interaction could provide critical information in understanding the pathogenicity of C. albicans.

Developing a chronic model of Candida albicans cerebral mycosis through gut colonization

Recent evidence suggests that Alzheimer's Disease (AD) is linked to fungal brain infections. We have previously established an acute model of cerebral mycosis by intravenously injecting the pathogenic yeast Candida albicans. The resulting infection induces mild transient memory deficits and fungal induced glial granulomas consisting of microglia and amyloid β deposits surrounding yeast aggregates. This structure essentially duplicates AD's characteristic senile plaque. AD involves numerous senile plaques and tauopathy that presumably accrue over many years potentially from chronic infection.

Bioactivity and Metabolome Mining of Deep-Sea Sediment-Derived Microorganisms Reveal New Hybrid PKS-NRPS Macrolactone from Aspergillus versicolor PS108-62

Despite low temperatures, poor nutrient levels and high pressure, microorganisms thrive in deep-sea environments of polar regions. The adaptability to such extreme environments renders deep-sea microorganisms an encouraging source of novel, bioactive secondary metabolites. In this study, we isolated 77 microorganisms collected by a remotely operated vehicle from the seafloor in the Fram Strait, Arctic Ocean (depth of 2454 m). Thirty-two bacteria and six fungal strains that represented the phylogenetic diversity of the isolates were cultured using an One-Strain-Many-Compounds (OSMAC) approach. The crude EtOAc extracts were tested for antimicrobial and anticancer activities. While antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecium was common for many isolates, only two bacteria displayed anticancer activity, and two fungi inhibited the pathogenic yeast Candida albicans. Due to bioactivity against C. albicans and rich chemical diversity based on molecular network-based untargeted metabolomics, Aspergillus versicolor PS108-62 was selected for an in-depth chemical investigation. A chemical work-up of the SPE-fractions of its dichloromethane subextract led to the isolation of a new PKS-NRPS hybrid macrolactone, versicolide A (1), a new quinazoline (-)-isoversicomide A (3), as well as three known compounds, burnettramic acid A (2), cyclopenol (4) and cyclopenin (5). Their structures were elucidated by a combination of HRMS, NMR, [α]D, FT-IR spectroscopy and computational approaches. Due to the low amounts obtained, only compounds 2 and 4 could be tested for bioactivity, with 2 inhibiting the growth of C. albicans (IC50 7.2 µg/mL). These findings highlight, on the one hand, the vast potential of the genus Aspergillus to produce novel chemistry, particularly from underexplored ecological niches such as the Arctic deep sea, and on the other, the importance of untargeted metabolomics for selection of marine extracts for downstream chemical investigations.

The Pga59 cell wall protein is an amyloid forming protein involved in adhesion and biofilm establishment in the pathogenic yeast Candida albicans

The human commensal fungus Candida albicans can attach to epithelia or indwelling medical devices and form biofilms, that are highly tolerant to antifungal drugs and can evade the immune response. The cell surface protein Pga59 has been shown to influence adhesion and biofilm formation. Here, we present evidence that Pga59 displays amyloid properties. Using electron microscopy, staining with an amyloid fibre-specific dye and X-ray diffraction experiments, we showed that the predicted amyloid-forming region of Pga59 is sufficient to build up an amyloid fibre in vitro and that recombinant Pga59 can also adopt a cross-β amyloid fibre architecture. Further, mutations impairing Pga59 amyloid assembly led to diminished adhesion to substrates and reduced biofilm production. Immunogold labelling on amyloid structures extracted from C. albicans revealed that Pga59 is used by the fungal cell to assemble amyloids within the cell wall in response to adhesion. Altogether, our results suggest that Pga59 amyloid properties are used by the fungal cell to mediate cell-substrate interactions and biofilm formation.

In English

The coronavirus pandemic has increased interest in antibacterial agents containing bioactive metals, for which zeolites are promising carriers. On the other hand, zeolite adsorbents and ion exchangers containing bioactive metals and endowed with bactericidal properties are promising for water treatment and other environmental and medical applications.Silver-, copper-, and zinc-containing microporous materials have been prepared on the base of natural analcime,phillipsite and heulandite from Georgian manifestations using ion-exchange reactions between zeolite microcrystals and a salt of a corresponding transition metal in the solid phase followed by washing with distilled water. Synthesized in such way adsorbent-ion-exchangers are characterized by chemical composition based on the X-ray energy dispersion spectra, powder X-ray diffraction patterns, Fourier transform infra-red spectra and low-temperature adsorption-desorption isotherms of N2. Obtained materials remain the zeolite crystal structure and contain 130–230 mg/g of silver, 65–72 mg/g of copper, and 58–86 mg/g of zinc, as compared with modified samples of synthetic type A zeolite containing up to 380 mg/g of silver, 150 mg/g of copper, and 150 mg/g of zinc. Prepared metal-containing materials show bacteriostatic activity against Gram negative bacterium Escherichia coli, Gram positive bacteria Staphylococcus aureus and Bacillus subtilis, fungal pathogenic yeastCandida albicans, and a fungus Aspergilusniger, and natural zeolites enriched with biometals exhibit a synergistic effect – their mixtures have a higher bacteriostatic activity. It is shown that mixtures of copper and zinc forms have a higher activity than the silver-containing form, which is very important from a practical point of view for replacing expensive silver with cheaper copper and zinc. It has been found that the bacteriostatic activity of metal-containing zeolites is determined not only and not so much by the ions of bioactive metals released into the liquid medium, but an important role ininhibiting the growth of microorganisms plays a type of zeolite matrix. Despite the relatively low ion-exchange capacity, heulandite turned out to be a fairly effective matrix for bioactive metals.