Pathogenic Yeast Candida Albicans Research Articles

In vitro combination therapy using low dose clotrimazole and photodynamic therapy leads to enhanced killing of the dermatophyte Trichophyton rubrum.

BackgroundSuperficial infections of the skin and mucous membranes caused by dermatophyte fungi are amongst the most common and challenging infections to treat. Previously we demonstrated the phototoxic effects of photodynamic therapy (PDT) towards Trichophyton rubrum, using a green laser to photoactivate Rose Bengal (RB). The aim of this study was to evaluate whether we could; (1) achieve a similar effect using an inexpensive light-emitting diode (LED) to photoactivate RB and (2) to evaluate whether our PDT regime could be combined with standard antifungal drug therapy and increase its effectiveness.MethodsWe designed and built our own inexpensive green (530 nm) LED source and tested its efficacy as part our RB-PDT regime in vitro against T. rubrum. We also examined the potential benefits of incorporating PDT as part of combination therapy and whether the order in which this was done had an impact. First we subjected spore suspensions to sub-inhibitory concentrations of a number of antifungal agents (CLT, MCZ and TRB) for 72 hours followed by RB-PDT. Secondly we subjected spore suspensions to sub-inhibitory PDT followed by drug treatment and evaluated if there were any changes to the minimum inhibitory concentrations (MICs) of the drugs tested.ResultsThe optimal conditions for photoinactivation of T. rubrum using RB-PDT alone were 140 μM of RB and 24 J/cm2 of LED (equating to a 30-minute exposure). These parameters also caused a 100% reduction in the viability of the pathogenic yeast Candida albicans and the model fungus Saccharomyces cerevisiae. By combining our RB-PDT regime as an adjunct to antifungal drugs we were able to dramatically reduce the exposure times. Treatment of spore suspensions using a sub-inhibitory dose of clotrimazole (CLT) followed by RB-PDT, this order was critical, significantly reduced the exposure times required to achieve 100% inhibition of T. rubrum to 15 minutes as compared to RB-PDT alone.ConclusionsThe combination of antifungal drug and RB-PDT represents an attractive alternative to the current antifungal therapies used to treat superficial fungal diseases. Our approach has the potential to reduce treatment times and drug dosages which can also reduce drug toxicity and improve patient compliance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0261-z) contains supplementary material, which is available to authorized users.

Characterization of four new antifungal yanuthones from Aspergillus niger.

Four new yanuthone analogs (1-4) were isolated from the filamentous fungus Aspergillus niger. The structures of the new compounds were elucidated on the basis of UHPLC-DAD-HRMS data and one-dimensional and two-dimensional NMR spectroscopy. Labeling studies with (13)C8-6-methylsalicylic acid identified three class I yanuthones originating from the polyketide 6-methylsalicylic acid (yanuthone K, L and M (1-3)) and a class II yanuthone, which was named yanuthone X2 (4). The four new compounds were tested toward the pathogenic yeast Candida albicans and all displayed antifungal activity. Yanuthone X2 represents the first example of a bioactive class II yanuthone, demonstrating the pharmaceutical potential of this class.

Roles of Edc3 in the oxidative stress response and CaMCA1-encoded metacaspase expression in Candida albicans.

The Edc3 protein is an enhancer of mRNA decapping, and acts as a scaffold protein for the mRNA granules that are known as processing bodies in yeast. In the pathogenic yeast Candida albicans, various stresses, such as glucose depletion, oxidative stress, and filamentation defects, induce the accumulation of processing bodies. Here, we report that the edc3/edc3 deletion strain showed increased resistance to various stresses, including hydrogen peroxide, acetic acid, and high temperature. Oxidative stress is known to induce the intracellular accumulation of reactive oxygen species (ROS) and apoptotic cell death in C. albicans. We found that the ROS level was lower in edc3/edc3 cells than in wild-type cells following oxidative stress. We also observed that expression of the metacaspase gene CaMCA1 was decreased in edc3/edc3 cells. Overexpression of CaMCA1 suppressed the decreased accumulation of ROS and the increased resistance to hydrogen peroxide in edc3/edc3 cells. The catalase Cat1 and the superoxide dismutase Sod1 were upregulated in edc3/edc3 cells as compared with wild-type cells. On the basis of these findings, we suggest that EDC3 plays a critical role in the expression of CaMCA1 and the oxidative stress response in C. albicans.

Origin replication complex binding, nucleosome depletion patterns, and a primary sequence motif can predict origins of replication in a genome with epigenetic centromeres.

ABSTRACTOrigins of DNA replication are key genetic elements, yet their identification remains elusive in most organisms. In previous work, we found that centromeres contain origins of replication (ORIs) that are determined epigenetically in the pathogenic yeast Candida albicans. In this study, we used origin recognition complex (ORC) binding and nucleosome occupancy patterns in Saccharomyces cerevisiae and Kluyveromyces lactis to train a machine learning algorithm to predict the position of active arm (noncentromeric) origins in the C. albicans genome. The model identified bona fide active origins as determined by the presence of replication intermediates on nondenaturing two-dimensional (2D) gels. Importantly, these origins function at their native chromosomal loci and also as autonomously replicating sequences (ARSs) on a linear plasmid. A “mini-ARS screen” identified at least one and often two ARS regions of ≥100 bp within each bona fide origin. Furthermore, a 15-bp AC-rich consensus motif was associated with the predicted origins and conferred autonomous replicating activity to the mini-ARSs. Thus, while centromeres and the origins associated with them are epigenetic, arm origins are dependent upon critical DNA features, such as a binding site for ORC and a propensity for nucleosome exclusion.

Flippase (FLP) recombinase-mediated marker recycling in the dermatophyte Arthroderma vanbreuseghemii

Biological processes can be elucidated by investigating complex networks of relevant factors and genes. However, this is not possible in species for which dominant selectable markers for genetic studies are unavailable. To overcome the limitation in selectable markers for the dermatophyte Arthroderma vanbreuseghemii (anamorph: Trichophyton mentagrophytes), we adapted the flippase (FLP) recombinase-recombination target (FRT) site-specific recombination system from the yeast Saccharomyces cerevisiae as a selectable marker recycling system for this fungus. Taking into account practical applicability, we designed FLP/FRT modules carrying two FRT sequences as well as the flp gene adapted to the pathogenic yeast Candida albicans (caflp) or a synthetic codon-optimized flp (avflp) gene with neomycin resistance (nptII) cassette for one-step marker excision. Both flp genes were under control of the Trichophyton rubrum copper-repressible promoter (PCTR4). Molecular analyses of resultant transformants showed that only the avflp-harbouring module was functional in A. vanbreuseghemii. Applying this system, we successfully produced the Ku80 recessive mutant strain devoid of any selectable markers. This strain was subsequently used as the recipient for sequential multiple disruptions of secreted metalloprotease (fungalysin) (MEP) or serine protease (SUB) genes, producing mutant strains with double MEP or triple SUB gene deletions. These results confirmed the feasibility of this system for broad-scale genetic manipulation of dermatophytes, advancing our understanding of functions and networks of individual genes in these fungi.

SAGA/ADA complex subunit Ada2 is required for Cap1- but not Mrr1-mediated upregulation of the Candida albicans multidrug efflux pump MDR1.

Overexpression of the multidrug efflux pump MDR1 is one mechanism by which the pathogenic yeast Candida albicans develops resistance to the antifungal drug fluconazole. The constitutive upregulation of MDR1 in fluconazole-resistant, clinical C. albicans isolates is caused by gain-of-function mutations in the zinc cluster transcription factor Mrr1. It has been suggested that Mrr1 activates MDR1 transcription by recruiting Ada2, a subunit of the SAGA/ADA coactivator complex. However, MDR1 expression is also regulated by the bZIP transcription factor Cap1, which mediates the oxidative stress response in C. albicans. Here, we show that a hyperactive Mrr1 containing a gain-of-function mutation promotes MDR1 overexpression independently of Ada2. In contrast, a C-terminally truncated, hyperactive Cap1 caused MDR1 overexpression in a wild-type strain but only weakly in mutants lacking ADA2. In the presence of benomyl or H2O2, compounds that induce MDR1 expression in an Mrr1- and Cap1-dependent fashion, MDR1 was upregulated with the same efficiency in wild-type and ada2Δ cells. These results indicate that Cap1, but not Mrr1, recruits Ada2 to the MDR1 promoter to induce the expression of this multidrug efflux pump and that Ada2 is not required for MDR1 overexpression in fluconazole-resistant C. albicans strains containing gain-of-function mutations in Mrr1.

Cold-active antibacterial and antifungal activities and antibiotic resistance of bacteria isolated from an alpine hydrocarbon-contaminated industrial site

Selection pressure in hydrocarbon-contaminated soils may lead not only to increased microbial resistance to antibiotics, but also to increased capacity of the soil indigenous population to produce antimicrobial compounds. Therefore, we studied the antibiotic resistance pattern and antibacterial and/or antifungal activities of 47 bacterial strains isolated from an industrial alpine site heavily polluted with petroleum hydrocarbons. Resistance to penicillin was more widespread (49%) than resistance to chloramphenicol or rifampicin (28%) or streptomycin (26%). Only 9% of the strains were resistant to tetracycline. The ability to produce cold-active (10 °C) antimicrobial compounds was tested by using human pathogenic bacteria (Escherichia coli, Shigella flexneri, Salmonella enterica, Pseudomonas aeruginosa, Staphylococcus aureus) and yeasts (Candida albicans, Cryptococcus neoformans) as indicator microorganisms. About two-thirds of the 47 tested strains produced compounds that inhibited growth of at least one indicator microorganism. Six strains inhibited growth of both bacteria and yeast indicators; 12 and 16 strains showed either antibacterial or antifungal activity, respectively. The most versatile bacteria with regard to multiple antibiotic resistance and antimicrobial activity belonged to Actinobacteria or Gammaproteobacteria. The antimicrobial compounds produced by three Pseudomonas spp. and two Serratia spp. strains were characterized in more detail by TLC and HPLC. Depending on the sensitivity of growth inhibition to enzymes, the compounds produced by the three pseudomonads contained a proteinaceous component.

Control of morphogenesis, protease secretion and gene expression in Candida albicans by the preferred nitrogen source ammonium.

Micro-organisms sense the availability of nutrients in their environment to control cellular behaviour and the expression of transporters and enzymes that are required for the utilization of these nutrients. In the pathogenic yeast Candida albicans, the preferred nitrogen source ammonium suppresses the switch from yeast to filamentous growth in response to certain stimuli, and it also represses the secretion of proteases, which are required for the utilization of proteins as an alternative nitrogen source. To investigate whether C. albicans senses the availability of ammonium in the extracellular environment or if ammonium uptake into the cell is required to regulate morphogenesis and gene expression, we compared the behaviour of wild-type cells and ammonium uptake-deficient mutants in the presence and absence of extracellular ammonium. Arginine-induced filamentous growth was suppressed by ammonium in the wild-type, but not in mutants lacking the ammonium permeases Mep1 and Mep2. Similarly, ammonium suppressed protease secretion and extracellular protein degradation in the wild-type, but not in mutants lacking the ammonium transporters. By comparing the gene expression profiles of C. albicans grown in the presence of low or high ammonium concentrations, we identified a set of genes whose expression is controlled by nitrogen availability. The repression of genes involved in the utilization of alternative nitrogen sources, which occurred under ammonium-replete conditions in the wild-type, was abrogated in mep1Δ mep2Δ mutants. These results demonstrate that C. albicans does not respond to the presence of sufficient amounts of the preferred nitrogen source ammonium by sensing its availability in the environment. Instead, ammonium has to be taken up into the cell to control morphogenesis, protease secretion and gene expression.

Chemical Composition Antioxidant and Antimicrobial Activities of the Essential Oils of Matricaria aurea Loefl. Growing in Tunisia

The present study describes the chemical composition, antibacterial, antifungal and antioxidant activities of essential oils isolated by steam distillation from the aerial parts and roots of the Tunisian Matricaria aurea Loefl. The chemical composition of essential oils was analyzed by gas chromatography/mass spectrometry (GC-MS). 105 components were identified, of which 1,5 bis (dicyclohexylphosphino)-pentane (44.7 %) was the main compound in leaves. These oils were subjected to screening for their possible antioxidant activities by using the ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl radical) methods and compared to the synthetic antioxidant Trolox. The inhibitory activity of M. aurea Loefl. essential oils against Gram-positive bacteria was significantly higher than against Gram-negative ones, Both pathogenic yeasts Candida albicans ATCC 9008 and Candida parapsilosis CECT 13009 were all resistant to the tested oils. Our results demonstrate that the essential oils of M. aurea possessing antioxidant and antimicrobial activities might be a natural potential source of preservative used in food and other allied industries.

Rad51-Rad52 mediated maintenance of centromeric chromatin in Candida albicans.

Specification of the centromere location in most eukaryotes is not solely dependent on the DNA sequence. However, the non-genetic determinants of centromere identity are not clearly defined. While multiple mechanisms, individually or in concert, may specify centromeres epigenetically, most studies in this area are focused on a universal factor, a centromere-specific histone H3 variant CENP-A, often considered as the epigenetic determinant of centromere identity. In spite of variable timing of its loading at centromeres across species, a replication coupled early S phase deposition of CENP-A is found in most yeast centromeres. Centromeres are the earliest replicating chromosomal regions in a pathogenic budding yeast Candida albicans. Using a 2-dimensional agarose gel electrophoresis assay, we identify replication origins (ORI7-LI and ORI7-RI) proximal to an early replicating centromere (CEN7) in C. albicans. We show that the replication forks stall at CEN7 in a kinetochore dependent manner and fork stalling is reduced in the absence of the homologous recombination (HR) proteins Rad51 and Rad52. Deletion of ORI7-RI causes a significant reduction in the stalled fork signal and an increased loss rate of the altered chromosome 7. The HR proteins, Rad51 and Rad52, have been shown to play a role in fork restart. Confocal microscopy shows declustered kinetochores in rad51 and rad52 mutants, which are evidence of kinetochore disintegrity. CENP-ACaCse4 levels at centromeres, as determined by chromatin immunoprecipitation (ChIP) experiments, are reduced in absence of Rad51/Rad52 resulting in disruption of the kinetochore structure. Moreover, western blot analysis reveals that delocalized CENP-A molecules in HR mutants degrade in a similar fashion as in other kinetochore mutants described before. Finally, co-immunoprecipitation assays indicate that Rad51 and Rad52 physically interact with CENP-ACaCse4 in vivo. Thus, the HR proteins Rad51 and Rad52 epigenetically maintain centromere functioning by regulating CENP-ACaCse4 levels at the programmed stall sites of early replicating centromeres.

Screening of Compounds from an FDA-Approved Drug Library for the Ability to Inhibit Aspartic Protease Secretion from the Pathogenic Yeast Candida albicans

The pathogenic fungus Candida albicans causes disseminated candidiasis with a poor prognosis in immunocompromised hosts. Secreted aspartyl protease (Sap) from the microorganism acts as a hydrolase to facilitate invasion into host tissues. Inhibition of Candida Sap activity could be a new treatment strategy for candidiasis. In the present study, we screened compounds from an FDA-approved drug library, Screen-Well, for their ability to inhibit Candida Sap activity. Sixteen compounds (piroxicam, carbidopa, nisoldipine, cerivastatin, fluvastatin, mycophenolic acid, rapamycin, bleomycin, bortezomib, 5-fluorouracil, floxuridine, fumagillin, pentamidine, albendazole, fenbendazole, and amprenavir) inhibited Sap activity in a dose-dependent manner in vitro, although strain differences in the activity of the compounds were observed. Our study shows that existing drug compounds have the potential to inhibit Sap activity.

Quantitative Expression of the Candida albicans Aspartyl Proteinase Genes SAP7, SAP8, SAP9, SAP10 in Human Serum in vitro

The different members of the secreted aspartyl proteinase (Sap) family of the human pathogenic yeast Candida albicans are proposed to play different roles during infection and are differentially expressed at various body sites. In recent reports, expression analysis has focused on the genes SAP1-6, while the expression pattern of SAP7-10 was less well studied. We analyzed the SAP7-SAP10 expression profile of C. albicans under human serum influence that may be elucidated in the course of blood infection in humans and how this in vitro expression profile is associated with hyphal formation. The phenotypes of strains were examined under scanning electron microscopy. Quantitative RT-PCR (2-(deltadeltaC)T) was used to monitor SAP expression of C. albicans wild type cells and mutants lacking SAP9 and/or SAP10. Of the four analyzed SAP genes, only SAP7 was detectably induced in the double mutant and in the wild type strains in the model that mimics bloodstream infections. On the other hand, in the wild types (isolate 83 and CAF2-1), SAP7 was expressed 0.8- or 0.4-fold less than SAP10, respectively. Our findings suggest that Sap7 may respond to the challenge of the human blood environment. Furthermore, the results support the notion that compensatory upregulation of SAP7 and SAP8 in the deltasap9/deltasap10 mutant occurs in these conditions. SAP7-10 expression was strain-specific. Our findings point to a link between morphogenesis and expression of SAP9 in serum, where these conditions induce both hyphae and SAP9, but temporal gene expression patterns might be controlled by other factors.

Characterization of the recombinant Candida albicans β-1,2-mannosyltransferase that initiates the β-mannosylation of cell wall phosphopeptidomannan

The presence of β-mannosides in their cell walls confers specific features on the pathogenic yeasts Candida albicans and Candida glabrata compared with non-pathogenic yeasts. In the present study, we investigated the enzymatic properties of Bmt1 (β-mannosyltransferase 1), a member of the recently identified β-mannosyltransferase family, from C. albicans. A recombinant soluble enzyme lacking the N-terminal region was expressed as a secreted protein from the methylotrophic yeast Pichia pastoris. In parallel, functionalized natural oligosaccharides isolated from Saccharomyces cerevisiae and a C. albicans mutant strain, as well as synthetic α-oligomannosides, were prepared and used as potential acceptor substrates. Bmt1p preferentially utilizes substrates containing linear chains of α-1,2-linked mannotriose or mannotetraose. The recombinant enzyme consecuti-vely transfers two mannosyl units on to these acceptors, leading to the production of α-mannosidase-resistant oligomannosides. NMR experiments further confirmed the presence of a terminal βMan (β-1,2-linked mannose) unit in the first enzyme product. In the future, a better understanding of specific β-1,2-mannosyltransferase molecular requirements will help the design of new potential antifungal drugs.

Antifungal properties of nanosized ZnS particles synthesised by sonochemical precipitation

Zinc sulphide (ZnS) nanoparticles, synthesised by a sonochemical route employing zinc chloride and sodium sulphide, displayed significant antifungal properties against the pathogenic yeast Candida albicans (MTCC 227) at a minimum fungicidal concentration of 300 μg ml−1. The antifungal properties of zinc sulphide particles is attributed to the generation of reactive oxygen species due to the interaction of the nanoparticles with water. Additionally, the presence of Zn in the zone of inhibition and the absence of antifungal effects for large micron sized particles of ZnS suggest a size induced effect leading to perturbation of fungal cell membranes, resulting in growth inhibition.

Variation of the Chemical Composition and Antimicrobial Activity of the Essential Oils of Natural Populations of Tunisian Daucus carota L. (Apiaceae)

The essential oils of Daucus carota L. (Apiaceae) seeds sampled from ten wild populations spread over northern Tunisia were characterized by GC-FID and GC/MS analyses. In total, 36 compounds were identified in the D. carota seed essential oils, with a predominance of sesquiterpene hydrocarbons in most samples (22.63-89.93% of the total oil composition). The main volatile compounds identified were β-bisabolene (mean content of 39.33%), sabinene (8.53%), geranyl acetate (7.12%), and elemicin (6.26%). The volatile composition varied significantly across the populations, even for oils of populations harvested in similar areas. The chemometric principal component analysis and the hierarchical clustering identified four groups, each corresponding to a composition-specific chemotype. The in vitro antimicrobial activity of the isolated essential oils was preliminarily evaluated, using the disk-diffusion method, against one Gram-positive (Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Salmonella typhimurium), as well as against a pathogenic yeast (Candida albicans). All tested essential oils exhibited interesting antibacterial and antifungal activities against the assayed microorganisms.

Kch1 Family Proteins Mediate Essential Responses to Endoplasmic Reticulum Stresses in the Yeasts Saccharomyces cerevisiae and Candida albicans

The activation of a high affinity Ca(2+) influx system (HACS) in the plasma membrane is required for survival of yeast cells exposed to natural or synthetic inhibitors of essential processes (secretory protein folding or sterol biosynthesis) in the endoplasmic reticulum (ER). The mechanisms linking ER stress to HACS activation are not known. Here we show that Kch1, a recently identified low affinity K(+) transporter in the plasma membrane of Saccharomyces cerevisiae, is up-regulated in response to several ER stressors and necessary for HACS activation. The activation of HACS required extracellular K(+) and was also dependent on the high affinity K(+) transporters Trk1 and Trk2. However, a paralog of Kch1 termed Kch2 was not expressed and not necessary for HACS activation in these conditions. The pathogenic yeast Candida albicans carries only one homolog of Kch1/Kch2, and homozygous knock-out mutants were similarly deficient in the activation of HACS during the responses to tunicamycin. However, the Kch1 homolog was not necessary for HACS activation or cell survival in response to several clinical antifungals (azoles, allylamines, echinocandins) that target the ER or cell wall. Thus, Kch1 family proteins represent a conserved linkage between HACS and only certain classes of ER stress in these yeasts.

Activation of the Cph1-Dependent MAP Kinase Signaling Pathway Induces White-Opaque Switching in Candida albicans

Depending on the environmental conditions, the pathogenic yeast Candida albicans can undergo different developmental programs, which are controlled by dedicated transcription factors and upstream signaling pathways. C. albicans strains that are homozygous at the mating type locus can switch from the normal yeast form (white) to an elongated cell type (opaque), which is the mating-competent form of this fungus. Both white and opaque cells use the Ste11-Hst7-Cek1/Cek2 MAP kinase signaling pathway to react to the presence of mating pheromone. However, while opaque cells employ the transcription factor Cph1 to induce the mating response, white cells recruit a different downstream transcription factor, Tec1, to promote the formation of a biofilm that facilitates mating of opaque cells in the population. The switch from the white to the opaque cell form is itself induced by environmental signals that result in the upregulation of the transcription factor Wor1, the master regulator of white-opaque switching. To get insight into the upstream signaling pathways controlling the switch, we expressed all C. albicans protein kinases from a tetracycline-inducible promoter in a switching-competent strain. Screening of this library of strains showed that a hyperactive form of Ste11 lacking its N-terminal domain (Ste11ΔN467) efficiently stimulated white cells to switch to the opaque phase, a behavior that did not occur in response to pheromone. Ste11ΔN467-induced switching specifically required the downstream MAP kinase Cek1 and its target transcription factor Cph1, but not Cek2 and Tec1, and forced expression of Cph1 also promoted white-opaque switching in a Wor1-dependent manner. Therefore, depending on the activation mechanism, components of the pheromone-responsive MAP kinase pathway can be reconnected to stimulate an alternative developmental program, switching of white cells to the mating-competent opaque phase.

Species-specific activation of Cu/Zn SOD by its CCS copper chaperone in the pathogenic yeast Candida albicans

Candida albicans is a pathogenic yeast of important public health relevance. Virulence of C. albicans requires a copper and zinc containing superoxide dismutase (SOD1), but the biology of C. albicans SOD1 is poorly understood. To this end, C. albicans SOD1 activation was examined in baker's yeast (Saccharomyces cerevisiae), a eukaryotic expression system that has proven fruitful for the study of SOD1 enzymes from invertebrates, plants, and mammals. In spite of the 80% similarity between S. cerevisiae and C. albicans SOD1 molecules, C. albicans SOD1 is not active in S. cerevisiae. The SOD1 appears incapable of productive interactions with the copper chaperone for SOD1 (CCS1) of S. cerevisiae. C. albicans SOD1 contains a proline at position 144 predicted to dictate dependence on CCS1. By mutation of this proline, C. albicans SOD1 gained activity in S. cerevisiae, and this activity was independent of CCS1. We identified a putative CCS1 gene in C. albicans and created heterozygous and homozygous gene deletions at this locus. Loss of CCS1 resulted in loss of SOD1 activity, consistent with its role as a copper chaperone. C. albicans CCS1 also restored activity to C. albicans SOD1 expressed in S. cerevisiae. C. albicans CCS1 is well adapted for activating its partner SOD1 from C. albicans, but not SOD1 from S. cerevisiae. In spite of the high degree of homology between the SOD1 and CCS1 molecules in these two fungal species, there exists a species-specific barrier in CCS-SOD interactions which may reflect the vastly different lifestyles of the pathogenic versus the noninfectious yeast.

Pathogenic Yeasts Deploy Cell Surface Receptors to Acquire Iron in Vertebrate Hosts

Pathogenic Yeasts Deploy Cell Surface Receptors to Acquire Iron in Vertebrate Hosts

The Diversity and Antimicrobial Activity of Preussia sp. Endophytes Isolated from Australian Dry Rainforests

Limited knowledge currently exists regarding species diversity and antimicrobial activity of endophytic isolates of Preussia within Australia. This report describes endophytic Preussia species that were identified through molecular analysis of the internal transcribed spacer region. Screening for antimicrobial secondary metabolites was determined by testing crude ethyl acetate (EtOAc) extracts derived from fungal mycelia against a panel of ATCC type strains which included Bacillus cereus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Serratia marcescens, methicillin-resistant Staphylococcus aureus (MRSA) and the opportunist yeast pathogen Candida albicans. Subsequently, high-performance liquid chromatography generated fractions of bioactive EtOAc extracts which were subject to confirmatory testing using the Clinical and Laboratory Standards Institute reference microdilution antimicrobial activity assay. A total of 18 Preussia were isolated from nine host plants with 6/18 having a<97% sequence similarity to other known species in Genbank, suggesting that they are new species. In preliminary screening, 13/18 Preussia isolates revealed antimicrobial activity against at least one of the microbes tested, whilst 6/18 isolates, including 4/6 putative new species showed specific antimicrobial activity against MRSA and C. albicans. These results highlight the antimicrobial potential of Australian Preussia spp. and also the importance of Australian dry rainforests as an untapped repository of potentially significant bioactive compounds.