Publications by authors named "István Pócsi"

132 Publications

How to characterize a strain? Clonal heterogeneity in industrial Saccharomyces influences both phenotypes and heterogeneity in phenotypes.

Yeast 2021 Apr 12. Epub 2021 Apr 12.

Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Egyetem tér 1, 4032, Hungary.

Populations of microbes are constantly evolving heterogeneity that selection acts upon, yet heterogeneity is non-trivial to assess methodologically. The necessary practice of isolating single cell colonies and thus, subclone lineages for establishing, transferring, and using a strain results in single-cell bottlenecks with a generally neglected effect on the characteristics of the strain itself. Here, we present evidence that various subclone lineages for industrial yeasts sequenced for recent genomic studies show considerable differences, ranging from loss-of-heterozygosity to aneuploidies. Subsequently, we assessed whether phenotypic heterogeneity is also observable in industrial yeast, by individually testing subclone lineages obtained from products. Phenotyping of industrial yeast samples and their newly isolated subclones showed that single-cell bottlenecks during isolation can indeed considerably influence the observable phenotype. Next, we decoupled fitness distributions on the level of individual cells from clonal interference by plating single cell colonies and quantifying colony area distributions. We describe and apply an approach using statistical modeling to compare the heterogeneity in phenotypes accross samples and subclone lineages. One strain was further used to show how individual subclonal lineages are remarkably different not just in phenotype, but also in the level of heterogeneity in phenotype. With these observations, we call attention to the fact that choosing an initial clonal lineage from an industrial yeast strain may vastly influence downstream performances and observations on karyotype, phenotype, and also on heterogeneity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/yea.3562DOI Listing
April 2021

Physical and Chemical Methods for Reduction in Aflatoxin Content of Feed and Food.

Toxins (Basel) 2021 Mar 12;13(3). Epub 2021 Mar 12.

Institute of Nutrition, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Böszörményi str. 138, H-4032 Debrecen, Hungary.

Aflatoxins (AFs) are among the most harmful fungal secondary metabolites imposing serious health risks on both household animals and humans. The more frequent occurrence of aflatoxins in the feed and food chain is clearly foreseeable as a consequence of the extreme weather conditions recorded most recently worldwide. Furthermore, production parameters, such as unadjusted variety use and improper cultural practices, can also increase the incidence of contamination. In current aflatoxin control measures, emphasis is put on prevention including a plethora of pre-harvest methods, introduced to control infestations and to avoid the deleterious effects of aflatoxins on public health. Nevertheless, the continuous evaluation and improvement of post-harvest methods to combat these hazardous secondary metabolites are also required. Already in-use and emerging physical methods, such as pulsed electric fields and other nonthermal treatments as well as interventions with chemical agents such as acids, enzymes, gases, and absorbents in animal husbandry have been demonstrated as effective in reducing mycotoxins in feed and food. Although most of them have no disadvantageous effect either on nutritional properties or food safety, further research is needed to ensure the expected efficacy. Nevertheless, we can envisage the rapid spread of these easy-to-use, cost-effective, and safe post-harvest tools during storage and food processing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/toxins13030204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7999035PMC
March 2021

DUG pathway governs degradation of intracellular glutathione in .

Appl Environ Microbiol 2021 Feb 26. Epub 2021 Feb 26.

Department of Molecular Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary.

Glutathione (GSH) is an abundant tripeptide that plays a crucial role in shielding cellular macromolecules from various reactive oxygen and nitrogen species in fungi. Understanding GSH metabolism is of vital importance to deciphering redox regulation in these microorganisms. In the present study, to better understand the GSH metabolism in filamentous fungi, we investigate functions of the and genes in the model fungus These genes are orthologues of involved in cytosolic GSH degradation in the yeast.The deletion (Δ) of , , or both resulted in a moderate increase in the GSH content in the mycelia grown on glucose, reduced conidia production, and disturbed sexual development. In agreement with these observations, transcriptome data showed that genes encoding MAP kinase pathway elements () or regulatory proteins of conidiogenesis and sexual differentiation (, ) were down-regulated in the mutant.Deletion of and/or slowed down the depletion of GSH pools under carbon starvation. It also reduced accumulation of reactive oxygen species, decreased autolytic cell wall degradation and enzyme secretion but increased sterigmatocystin formation. Transcriptome data demonstrated that enzyme secretions - in contrast to mycotoxin production - were controlled at post-transcriptional level. We suggest that GSH connects starvation and redox regulation to each other: Cells utilize GSH as stored carbon source during starvation. The reduction of GSH content alters the redox state activating regulatory pathways responsible for carbon starvation stress responses.Glutathione (GSH) is a widely distributed tripeptide in both eukaryotes and prokaryotes. Owing to its very low redox potential, antioxidative character and high intracellular concentration, GSH profoundly shapes the redox status of cells. Our observations suggest that GSH metabolism and/or the redox status of cells plays a determinative role in several important aspects of fungal life, including oxidative stress defense, protein secretion, secondary metabolite production (including mycotoxin formation) as well as sexual and asexual differentiations. We demonstrated that even a slightly elevated GSH level can substantially disturb the homeostasis of fungi. This information could be important for development of new GSH producing strains or for any biotechnologically relevant processes where the GSH content, antioxidant capacity or oxidative stress tolerance of a fungal strain is manipulated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AEM.01321-20DOI Listing
February 2021

Biological Control and Mitigation of Aflatoxin Contamination in Commodities.

Toxins (Basel) 2021 Feb 1;13(2). Epub 2021 Feb 1.

Central Laboratory of Agricultural and Food Products, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Böszörményi str. 138, H-4032 Debrecen, Hungary.

Aflatoxins (AFs) are toxic secondary metabolites produced mostly by species. AF contamination entering the feed and food chain has been a crucial long-term issue for veterinarians, medicals, agroindustry experts, and researchers working in this field. Although different (physical, chemical, and biological) technologies have been developed, tested, and employed to mitigate the detrimental effects of mycotoxins, including AFs, universal methods are still not available to reduce AF levels in feed and food in the last decades. Possible biological control by bacteria, yeasts, and fungi, their excretes, the role of the ruminal degradation, pre-harvest biocontrol by competitive exclusion or biofungicides, and post-harvest technologies and practices based on biological agents currently used to alleviate the toxic effects of AFs are collected in this review. Pre-harvest biocontrol technologies can give us the greatest opportunity to reduce AF production on the spot. Together with post-harvest applications of bacteria or fungal cultures, these technologies can help us strictly reduce AF contamination without synthetic chemicals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/toxins13020104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7912779PMC
February 2021

Shed Light in the DaRk LineagES of the Fungal Tree of Life-STRES.

Life (Basel) 2020 Dec 19;10(12). Epub 2020 Dec 19.

Microbiology & Plant Pathology, University of California Riverside, Riverside, CA 92521, USA.

The polyphyletic group of black fungi within the Ascomycota (Arthoniomycetes, Dothideomycetes, and Eurotiomycetes) is ubiquitous in natural and anthropogenic habitats. Partly because of their dark, melanin-based pigmentation, black fungi are resistant to stresses including UV- and ionizing-radiation, heat and desiccation, toxic metals, and organic pollutants. Consequently, they are amongst the most stunning extremophiles and poly-extreme-tolerant organisms on Earth. Even though ca. 60 black fungal genomes have been sequenced to date, [mostly in the family Herpotrichiellaceae (Eurotiomycetes)], the class Dothideomycetes that hosts the largest majority of extremophiles has only been sparsely sampled. By sequencing up to 92 species that will become reference genomes, the "Shed light in The daRk lineagES of the fungal tree of life" (STRES) project will cover a broad collection of black fungal diversity spread throughout the Fungal Tree of Life. Interestingly, the STRES project will focus on mostly unsampled genera that display different ecologies and life-styles (e.g., ant- and lichen-associated fungi, rock-inhabiting fungi, etc.). With a resequencing strategy of 10- to 15-fold depth coverage of up to ~550 strains, numerous new reference genomes will be established. To identify metabolites and functional processes, these new genomic resources will be enriched with metabolomics analyses coupled with transcriptomics experiments on selected species under various stress conditions (salinity, dryness, UV radiation, oligotrophy). The data acquired will serve as a reference and foundation for establishing an encyclopedic database for fungal metagenomics as well as the biology, evolution, and ecology of the fungi in extreme environments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/life10120362DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7767062PMC
December 2020

Editorial: -Derived Mycotoxins in the Feed and Food Chain.

Front Microbiol 2020 11;11:606108. Epub 2020 Nov 11.

Institute of Sciences of Food Production, Italian National Research Council, Bari, Italy.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2020.606108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693537PMC
November 2020

Pre-Harvest Modelling and Mitigation of Aflatoxins in Maize in a Changing Climatic Environment-A Review.

Toxins (Basel) 2020 12 4;12(12). Epub 2020 Dec 4.

Agrometeorological and Agroecological Monitoring Centre, AKIT-DTTI, University of Debrecen, H4032 Debrecen, Hungary.

Aflatoxins (AFs) are harmful secondary metabolites produced by various moulds, among which is the major AF-producer fungus. These mycotoxins have carcinogenic or acute toxigenic effects on both humans and food producing animals and, therefore, the health risks and also the potential economic damages mounted by them have led to legal restrictions, and several countries have set maximum allowable limits for AF contaminations in food and feed. While colonization of food and feed and AF production by are highly supported by the climatic conditions in tropical and subtropical geographic regions, countries in the temperate climate zones are also increasingly exposed to AF-derived health risks due to climate change. In the present study, we have reviewed the available mathematical models as risk assessment tools to predict the possibility of infection and levels of AF contaminations in maize in a changing climatic environment. After highlighting the benefits and possible future improvements of these models, we summarize the current agricultural practices used to prevent or, at least, mitigate the deleterious consequences of AF contaminations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/toxins12120768DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7761929PMC
December 2020

FvmnSOD is involved in oxidative stress defence, mitochondrial stability and apoptosis prevention in Fusarium verticillioides.

J Basic Microbiol 2020 Nov 23;60(11-12):994-1003. Epub 2020 Nov 23.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

Superoxide dismutases are key enzymes in elimination of the superoxide anion radical (O ) generated intracellularly or by exogenous oxidative stress eliciting agents, like menadione. In this study, we investigated the physiological role of the manganese superoxide dismutase-encoding gene in Fusarium verticillioides via the construction of a gene deletion mutant, ΔFvmnSOD and comparing its phenotype with that of the wild-type parental strain and a ΔFvmnSOD' C strain, complemented with the functional manganese superoxide dismutase gene. Deletion of FvmnSOD had no effect on the relative intracellular superoxide ratio but increased the sensitivity of the fungus to menadione sodium bisulphite on Czapek-Dox stress agar plates. The lack of FvmnSOD caused changes in mitochondrial morphology and physiology: The volumetric ratio of these cell organelles in the second hyphal segment, as well as the total, the KCN-sensitive cytochrome c-dependent and the KCN+SHAM (salicylhidroxamic acid)-resistant residual respiration rates, were higher in the mutant as compared to the wild-type and the complemented strains. Nevertheless, changes in the respiration rates were attributable to the higher volumetric ratio of mitochondria found in the gene deletion mutant. Changes in the mitochondrial functions also brought about higher sensitivity to apoptotic cell death elicited by the Penicillium chrysogenum antifungal protein. The gene deletion mutant developed significantly thinner hyphae in comparison to the wild-type strain. Deletion of FvmnSOD had no effect on fumonisin B and B production of the fungus grown in Myro medium as a static culture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jobm.202000560DOI Listing
November 2020

FvatfA regulates growth, stress tolerance as well as mycotoxin and pigment productions in Fusarium verticillioides.

Appl Microbiol Biotechnol 2020 Sep 27;104(18):7879-7899. Epub 2020 Jul 27.

Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

FvatfA from the maize pathogen Fusarium verticillioides putatively encodes the Aspergillus nidulans AtfA and Schizasaccharomyces pombe Atf1 orthologous bZIP-type transcription factor, FvAtfA. In this study, a ΔFvatfA deletion mutant was constructed and then genetically complemented with the fully functional FvatfA gene. Comparing phenotypic features of the wild-type parental, the deletion mutant and the restored strains shed light on the versatile regulatory functions played by FvAtfA in (i) the maintenance of vegetative growth on Czapek-Dox and Potato Dextrose agars and invasive growth on unwounded tomato fruits, (ii) the preservation of conidiospore yield and size, (iii) the orchestration of oxidative (HO, menadione sodium bisulphite) and cell wall integrity (Congo Red) stress defences and (iv) the regulation of mycotoxin (fumonisins) and pigment (bikaverin, carotenoid) productions. Expression of selected biosynthetic genes both in the fumonisin (fum1, fum8) and the carotenoid (carRA, carB) pathways were down-regulated in the ΔFvatfA strain resulting in defected fumonisin production and considerably decreased carotenoid yields. The expression of bik1, encoding the polyketide synthase needed in bikaverin biosynthesis, was not up-regulated by the deletion of FvatfA meanwhile the ΔFvatfA strain produced approximately ten times more bikaverin than the wild-type or the genetically complemented strains. The abolishment of fumonisin production of the ΔFvatfA strain may lead to the development of new-type, biology-based mycotoxin control strategies. The novel information gained on the regulation of pigment production by this fungus can be interesting for experts working on new, Fusarium-based biomass and pigment production technologies. Key points • FvatfA regulates vegetative and invasive growths of F. verticillioides. • FvatfA also orchestrates oxidative and cell wall integrity stress defenses. • The ΔFvatfA mutant was deficient in fumonisin production. • FvatfA deletion resulted in decreased carotenoid and increased bikaverin yields.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00253-020-10717-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7447684PMC
September 2020

Analysis of fumonisin mycotoxins with capillary electrophoresis - mass spectrometry.

Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2020 Sep 21;37(9):1553-1563. Epub 2020 Jul 21.

Department of Inorganic and Analytical Chemistry, University of Debrecen , Debrecen, Hungary.

This paper demonstrates the development of an analytical method based on CE coupled to ESI-MS for the identification and quantification of fumonisin mycotoxins. Separation and detection parameters (pH of background electrolyte (BGE), organic modifier content, sheath liquid (SL) composition, MS mode and nebuliser pressure) were optimised. Ammonium formate/ammonia (pH = 9.5) with 10% ACN modifier was found the most suitable BGE. Positive mode MS was used for detection by scanning the m/z range of 400-1200. Separation was highly affected by the nebuliser pressure, a 25% improvement in peak resolution was achieved by applying the optimised parameters. The 'dilute and shoot' approach was applied to overcome disturbing effects caused by the matrix of fungi supernatant samples. The available sample volume affected the reproducibility of the measurements greatly: the scattering of peak intensities were between 4 and 11 RSD% instead of 27-195 RSD% for fumonisin B and fumonisin B when the available volume was ~200 µL instead of ~20 µL. Quantitative determinations were carried out in and culture supernatant (raw) and mycelium (cleaned up) samples. The optimised method enabled the detection of 11 fumonisins in inoculated rice samples; 2 of them were quantified based on external calibration and 4 other compounds with fumonisin-like formulas were detected.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/19440049.2020.1778797DOI Listing
September 2020

The Fungal Iron Chelator Desferricoprogen Inhibits Atherosclerotic Plaque Formation.

Int J Mol Sci 2020 Jul 3;21(13). Epub 2020 Jul 3.

HAS-UD Vascular Biology and Myocardial Pathophysiology Research Group, Hungarian Academy of Sciences, University of Debrecen, 4012 Debrecen, Hungary.

Hemoglobin, heme and iron are implicated in the progression of atherosclerosis. Therefore, we investigated whether the hydrophobic fungal iron chelator siderophore, desferricoprogen (DFC) inhibits atherosclerosis. DFC reduced atherosclerotic plaque formation in ApoE mice on an atherogenic diet. It lowered the plasma level of oxidized LDL (oxLDL) and inhibited lipid peroxidation in aortic roots. The elevated collagen/elastin content and enhanced expression of adhesion molecule VCAM-1 were decreased. DFC diminished oxidation of Low-density Lipoprotein (LDL) and plaque lipids catalyzed by heme or hemoglobin. Formation of foam cells, uptake of oxLDL by macrophages, upregulation of CD36 and increased expression of TNF-α were reduced by DFC in macrophages. TNF-triggered endothelial cell activation (vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecules (ICAMs), E-selectin) and increased adhesion of monocytes to endothelium were attenuated. The increased endothelial permeability and intracellular gap formation provoked by TNF-α was also prevented by DFC. DFC acted as a cytoprotectant in endothelial cells and macrophages challenged with a lethal dose of oxLDL and lowered the expression of stress-responsive heme oxygenase-1 as sublethal dose was employed. Saturation of desferrisiderophore with iron led to the loss of the beneficial effects. We demonstrated that DFC accumulated within the atheromas of the aorta in ApoE mice. DFC represents a novel therapeutic approach to control the progression of atherosclerosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21134746DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7369830PMC
July 2020

Supplementation of Aspergillus glaucus with gfdB gene encoding a glycerol 3-phosphate dehydrogenase in Aspergillus nidulans.

J Basic Microbiol 2020 Aug 8;60(8):691-698. Epub 2020 Jun 8.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

In Aspergillus nidulans, there are two putative glycerol 3-phosphate dehydrogenases encoded by the genes gfdA and gfdB, while the genome of the osmophilic Aspergillus glaucus harbors only the ortholog of the A. nidulans gfdA gene. Our aim was to insert the gfdB gene into the genome of A. glaucus, and we reached this goal with the adaptation of the Agrobacterium tumefaciens-mediated transformation method. We tested the growth of the gfdB-complemented A. glaucus strains on a medium containing 2 mol l sorbitol in the presence of oxidative stress generating agents such as tert-butyl hydroperoxide, H O , menadione sodium bisulfite, as well as the cell wall integrity stress-inducing agent Congo Red and the heavy metal stress eliciting CdCl . The growth of the complemented strains was significantly higher than that of the wild-type strain on media supplemented with these stress generating agents. The A. nidulans ΔgfdB mutant was also examined under the same conditions and resulted in a considerably lower growth than that of the control strain in all stress exposure experiments. Our results shed light on the fact that the gfdB gene from A. nidulans was also involved in the stress responses of the complemented A. glaucus strains supporting our hypothesis on the antioxidant function of GfdB in the Aspergilli. Nevertheless, the osmotolerant nature of A. glaucus could not be explained by the lack of the gfdB gene in A. glaucus, as we hypothesized earlier.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jobm.202000067DOI Listing
August 2020

Increased Cd biosorption capability of Aspergillus nidulans elicited by crpA deletion.

J Basic Microbiol 2020 Jul 25;60(7):574-584. Epub 2020 May 25.

Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

The P-type ATPase CrpA is an important Cu /Cd pump in the Aspergilli, significantly contributing to the heavy metal stress tolerance of these ascomycetous fungi. As expected, the deletion of crpA resulted in Cu /Cd -sensitive phenotypes in Aspergillus nidulans on stress agar plates inoculated with conidia. Nevertheless, paradoxical growth stimulations were observed with the ΔcrpA strain in both standard Cu stress agar plate experiments and cellophane colony harvest (CCH) cultures, when exposed to Cd . These observations reflect efficient compensatory mechanisms for the loss of CrpA operating under these experimental conditions. It is remarkable that the ΔcrpA strain showed a 2.7 times higher Cd biosorption capacity in CCH cultures, which may facilitate the development of new, fungal biomass-based bioremediation technologies to extract harmful Cd ions from the environment. The nullification of crpA also significantly changed the spatial distribution of Cu and Cd in CCH cultures, as demonstrated by the combined particle-induced X-ray emission and scanning transmission ion microscopy technique. Most important, the centers of gravity for Cu and Cd accumulations of the ΔcrpA colonies shifted toward the older regions as compared with wild-type surface cultures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jobm.202000112DOI Listing
July 2020

General stress response or adaptation to rapid growth in Aspergillus nidulans?

Fungal Biol 2020 05 28;124(5):376-386. Epub 2019 Oct 28.

Department of Molecular Biotechnology and Microbiology, University of Debrecen, Egyetem tér 1, Debrecen, 4032, Hungary. Electronic address:

Genome-wide transcriptional changes in Aspergillus nidulans induced by nine different stress conditions were evaluated to reveal the general environmental stress response gene set showing unidirectional expressional changes under various types of stress. Clustering the genes by their transcriptional changes was a useful technique for identifying large groups of co-regulated genes. Altogether, 1642 co-upregulated and 3916 co-downregulated genes were identified. Nevertheless, the co-regulated genes describe the difference between the transcriptomes recorded under the stress conditions tested and one chosen reference culture condition which is designated as the "unstressed" condition. Obviously, the corresponding transcriptional differences may be attributed to either the general stress response or the reference condition. Accordingly, reduced growth and increased transcription of certain antioxidative enzymes observed under stress may be interpreted as elements of the general stress response or as a feature of the "optimal growth" reference condition and decreased antioxidative protection due to "rapid growth" stress. Reversing the many to one comparison underlying the identification of co-regulated gene sets allows the same procedure to highlight changes under a single condition with respect to a set of other "background" conditions. As an example, we compared menadione treatment to our other conditions and identified downregulation of endoplasmic reticulum dependent processes and upregulation of iron-sulfur cluster assembly as well as glutathione-S-transferase genes as changes characteristic of MSB-treated cultures. Deletion of the atfA gene markedly altered the co-regulated gene sets primarily by changing the reference transcriptome; not by changing the stress responsiveness of genes. The functional characterization of AtfA-dependent co-regulated genes demonstrated the involvement of AtfA in the regulation of both vegetative growth and conidiogenesis in untreated cultures. Our data also suggested that the diverse effects of atfA gene deletion on the transcriptome under different stress conditions were the consequence of the altered transcription of several phosphorelay signal transduction system genes, including fphA, nikA, phkA, srrB, srrC, sskA and tcsB. Hopefully, this study will draw further attention to the importance of the proper selection of reference cultures in fungal transcriptomics studies especially when elements of specific stress responses are mapped.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.funbio.2019.10.009DOI Listing
May 2020

Characterization of gfdB, putatively encoding a glycerol 3-phosphate dehydrogenase in Aspergillus nidulans.

Fungal Biol 2020 05 11;124(5):352-360. Epub 2019 Oct 11.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary. Electronic address:

The genome of Aspergillus nidulans accommodates two glycerol 3-phosphate dehydrogenase genes, gfdA and gfdB. Previous studies confirmed that GfdA is involved in the osmotic stress defence of the fungus. In this work, the physiological role of GfdB was characterized via the construction and functional characterization of the gene deletion mutant ΔgfdB. Unexpectedly, ΔgfdB strains showed oxidative stress sensitivity in the presence of a series of well-known oxidants including tert-butyl-hydroperoxide (tBOOH), diamide as well as hydrogen peroxide. Moderate sensitivity of the mutant towards the cell wall stress inducing agent CongoRed was also observed. Hence, both Gfd isoenzymes contributed to the environmental stress defence of the fungus but their functions were stress-type-specific. Furthermore, the specific activities of certain antioxidant enzymes, like catalase and glutathione peroxidase, were lower in ΔgfdB hyphae than those recorded in the control strain. As a consequence, mycelia from ΔgfdB cultures accumulated reactive species at higher levels than the control. On the other hand, the specific glutathione reductase activity was higher in the mutant, most likely to compensate for the elevated intracellular oxidative species concentrations. Nevertheless, the efficient control of reactive species failed in ΔgfdB cultures, which resulted in reduced viability and, concomitantly, early onset of programmed cell death in mutant hyphae. Inactivation of gfdB brought about higher mannitol accumulation in mycelia meanwhile the erythritol production was not disturbed in unstressed cultures. After oxidative stress treatment with tBOOH, only mannitol was detected in both mutant and control mycelia and the accumulation of mannitol even intensified in the ΔgfdB strain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.funbio.2019.09.011DOI Listing
May 2020

The Third International Symposium on Fungal Stress - ISFUS.

Fungal Biol 2020 05 24;124(5):235-252. Epub 2020 Feb 24.

Universidade Brasil, São Paulo, SP, Brazil. Electronic address:

Stress is a normal part of life for fungi, which can survive in environments considered inhospitable or hostile for other organisms. Due to the ability of fungi to respond to, survive in, and transform the environment, even under severe stresses, many researchers are exploring the mechanisms that enable fungi to adapt to stress. The International Symposium on Fungal Stress (ISFUS) brings together leading scientists from around the world who research fungal stress. This article discusses presentations given at the third ISFUS, held in São José dos Campos, São Paulo, Brazil in 2019, thereby summarizing the state-of-the-art knowledge on fungal stress, a field that includes microbiology, agriculture, ecology, biotechnology, medicine, and astrobiology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.funbio.2020.02.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7438019PMC
May 2020

Rare earth element sequestration by biomass.

Environ Technol 2020 Mar 16:1-11. Epub 2020 Mar 16.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

The fungus could be shown to be a viable alternative for biosorption of valuable metals from solution. Fungal biomass can be obtained easily in high quantities as a waste of biofermentation processes, and used in a complex, multi-phase solution mimicking naturally occurring, mining-affected water samples. With test solution formulated after natural conditions, formation of secondary Al and Fe phases co-precipitating Ce was recorded in addition to specific biosorption of rare earth elements. Remarkably, the latter were removed from the solution despite the presence of high concentrations of interfering Fe and Al. The biomass was viable even after prolonged incubation in the metal solution, and minimal inhibitory concentrations for single metals were higher than those in the test solution. While precipitation/biosorption of Ce (maximal biosorption efficiency was 58.0 ± 22.3% after 6 h of incubation) coincided with the gross removal of Fe from the metal solution, Y (81.5 ± 11.3% efficiency, 24 h incubation) and Nd (87.4 ± 9.1% efficiency, 24 h incubation) were sequestered later, similarly to Ni and Zn. The biphasic binding pattern specific to single metals could be connected to dynamically changing pH and NH concentrations, which were attributed to the physiological changes taking place in starving biomass. The metals were found extracellularly in minerals associated with the cell wall, and intracellularly precipitated in the vacuoles. The latter process was explained with intracellular metal detoxification resulting in metal resistance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09593330.2020.1739146DOI Listing
March 2020

The and Their Mycotoxins: Metabolic Interactions With Plants and the Soil Biota.

Front Microbiol 2019 12;10:2921. Epub 2020 Feb 12.

Central Laboratory of Agricultural and Food Products, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Debrecen, Hungary.

Species of the highly diverse fungal genus are well-known agricultural pests, and, most importantly, producers of various mycotoxins threatening food safety worldwide. Mycotoxins are studied predominantly from the perspectives of human and livestock health. Meanwhile, their roles are far less known in nature. However, to understand the factors behind mycotoxin production, the roles of the toxins of must be understood from a complex ecological perspective, taking mold-plant, mold-microbe, and mold-animal interactions into account. The may switch between saprophytic and pathogenic lifestyles, and the production of secondary metabolites, such as mycotoxins, may vary according to these fungal ways of life. Recent studies highlighted the complex ecological network of soil microbiotas determining the niches that can fill in. Interactions with the soil microbiota and soil macro-organisms determine the role of secondary metabolite production to a great extent. While, upon infection of plants, metabolic communication including fungal secondary metabolites like aflatoxins, gliotoxin, patulin, cyclopiazonic acid, and ochratoxin, influences the fate of both the invader and the host. In this review, the role of mycotoxin producing species and their interactions in the ecosystem are discussed. We intend to highlight the complexity of the roles of the main toxic secondary metabolites as well as their fate in natural environments and agriculture, a field that still has important knowledge gaps.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2019.02921DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7029702PMC
February 2020

Antifungal Activity of an Original Amino-Isocyanonaphthalene (ICAN) Compound Family: Promising Broad Spectrum Antifungals.

Molecules 2020 Feb 18;25(4). Epub 2020 Feb 18.

Department of Applied Chemistry, Faculty of Science, University of Debrecen, 4010 Debrecen, Hungary.

Multiple drug resistant fungi pose a serious threat to human health, therefore the development of completely new antimycotics is of paramount importance. The in vitro antifungal activity of the original, 1-amino-5-isocyanonaphthalenes (ICANs) was evaluated against reference strains of clinically important species. Structure-activity studies revealed that the naphthalene core and the isocyano- together with the amino moieties are all necessary to exert antifungal activity. 1,1--dimethylamino-5-isocyanonaphthalene (DIMICAN), the most promising candidate, was tested further in vitro against clinical isolates of species, yielding a minimum inhibitory concentration (MIC) of 0.04-1.25 µg/mL. DIMICAN was found to be effective against intrinsically fluconazole resistant isolates, too. In vivo experiments were performed in a severly neutropenic murine model inoculated with a clinical strain of . Daily administration of 5 mg/kg DIMICAN intraperitoneally resulted in 80% survival even at day 13, whereas 100% of the control group died within six days. Based on these results, ICANs may become an effective clinical lead compound family against fungal pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/molecules25040903DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7070524PMC
February 2020

Functional characterization of the idtF and idtP genes in the Claviceps paspali indole diterpene biosynthetic gene cluster.

Folia Microbiol (Praha) 2020 Jun 19;65(3):605-613. Epub 2020 Feb 19.

Southwest Center for Natural Products Research, School of Natural Resources and the Environment, University of Arizona, Tucson, USA.

Claviceps paspali is used in the pharmaceutical industry for the production of ergot alkaloids. This fungus also biosynthesizes paspalitrems, indole diterpene (IDT) mycotoxins that cause significant economic losses in agriculture and represent safety concerns for ergot alkaloid manufacture. Here, we use Agrobacterium-mediated transformation to replace the idtP and the idtF genes in the IDT biosynthetic gene cluster of C. paspali with a selectable marker gene. We show that the ΔidtP knockout mutant produces paspaline, the first IDT intermediate of the pathway. The ΔidtF strain produces unprenylated IDTs such as paspalinine and paspaline. These experiments validate the function of idtP as the gene encoding the cytochrome P450 monooxygenase that oxidizes and demethylates paspaline to produce 13-desoxypaxilline, and that of idtF as the gene that encodes the α-prenyltransferase that prenylates paspalinine at the C20 or the C21 positions to yield paspalitrems A and C, respectively. In addition, we also show that axenic cultures of the wild type, the ΔidtP and the ΔidtF mutant C. paspali strains fail to produce an assembly of IDTs that are present in C. paspali-Paspalum spp. associations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12223-020-00777-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7244603PMC
June 2020

Toxicological and Medical Aspects of -Derived Mycotoxins Entering the Feed and Food Chain.

Front Microbiol 2019 9;10:2908. Epub 2020 Jan 9.

Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.

Due to Earth's changing climate, the ongoing and foreseeable spreading of mycotoxigenic s species has increased the possibility of mycotoxin contamination in the feed and food production chain. These harmful mycotoxins have aroused serious health and economic problems since their first appearance. The most potent -derived mycotoxins include aflatoxins, ochratoxins, gliotoxin, fumonisins, sterigmatocystin, and patulin. Some of them can be found in dairy products, mainly in milk and cheese, as well as in fresh and especially in dried fruits and vegetables, in nut products, typically in groundnuts, in oil seeds, in coffee beans, in different grain products, like rice, wheat, barley, rye, and frequently in maize and, furthermore, even in the liver of livestock fed by mycotoxin-contaminated forage. Though the mycotoxins present in the feed and food chain are well documented, the human physiological effects of mycotoxin exposure are not yet fully understood. It is known that mycotoxins have nephrotoxic, genotoxic, teratogenic, carcinogenic, and cytotoxic properties and, as a consequence, these toxins may cause liver carcinomas, renal dysfunctions, and also immunosuppressed states. The deleterious physiological effects of mycotoxins on humans are still a first-priority question. In food production and also in the case of acute and chronic poisoning, there are possibilities to set suitable food safety measures into operation to minimize the effects of mycotoxin contaminations. On the other hand, preventive actions are always better, due to the multivariate nature of mycotoxin exposures. In this review, the occurrence and toxicological features of major -derived mycotoxins are summarized and, furthermore, the possibilities of treatments in the medical practice to heal the deleterious consequences of acute and/or chronic exposures are presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2019.02908DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6962185PMC
January 2020

Adverse Effects, Transformation and Channeling of Aflatoxins Into Food Raw Materials in Livestock.

Front Microbiol 2019 11;10:2861. Epub 2019 Dec 11.

Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

Aflatoxins are wide-spread harmful carcinogenic secondary metabolites produced by species, which cause serious feed and food contaminations and affect farm animals deleteriously with acute or chronic manifestations of mycotoxicoses. On farm, both pre-harvest and post-harvest strategies are applied to minimize the risk of aflatoxin contaminations in feeds. The great economic losses attributable to mycotoxin contaminations have initiated a plethora of research projects to develop new, effective technologies to prevent the highly toxic effects of these secondary metabolites on domestic animals and also to block the carry-over of these mycotoxins to humans through the food chain. Among other areas, this review summarizes the latest findings on the effects of silage production technologies and silage microbiota on aflatoxins, and it also discusses the current applications of probiotic organisms and microbial products in feeding technologies. After ingesting contaminated foodstuffs, aflatoxins are metabolized and biotransformed differently in various animals depending on their inherent and acquired physiological properties. These mycotoxins may cause primary aflatoxicoses with versatile, species-specific adverse effects, which are also dependent on the susceptibility of individual animals within a species, and will be a function of the dose and duration of aflatoxin exposures. The transfer of these undesired compounds from contaminated feed into food of animal origin and the aflatoxin residues present in foods become an additional risk to human health, leading to secondary aflatoxicoses. Considering the biological transformation of aflatoxins in livestock, this review summarizes (i) the metabolism of aflatoxins in different animal species, (ii) the deleterious effects of the mycotoxins and their derivatives on the animals, and (iii) the major risks to animal health in terms of the symptoms and consequences of acute or chronic aflatoxicoses, animal welfare and productivity. Furthermore, we traced the transformation and channeling of Aspergillus-derived mycotoxins into food raw materials, particularly in the case of aflatoxin contaminated milk, which represents the major route of human exposure among animal-derived foods. The early and reliable detection of aflatoxins in feed, forage and primary commodities is an increasingly important issue and, therefore, the newly developed, easy-to-use qualitative and quantitative aflatoxin analytical methods are also summarized in the review.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2019.02861DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6917664PMC
December 2019

Deletion of the fungus specific protein phosphatase Z1 exaggerates the oxidative stress response in Candida albicans.

BMC Genomics 2019 Nov 19;20(1):873. Epub 2019 Nov 19.

Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.

Background: Candida albicans is an opportunistic pathogen which is responsible for widespread nosocomial infections. It encompasses a fungus specific serine/threonine protein phosphatase gene, CaPPZ1 that is involved in cation transport, cell wall integrity, oxidative stress response, morphological transition, and virulence according to the phenotypes of the cappz1 deletion mutant.

Results: We demonstrated that a short-term treatment with a sublethal concentration of tert-butyl hydroperoxide suppressed the growth of the fungal cells without affecting their viability, both in the cappz1 mutant and in the genetically matching QMY23 control strains. To reveal the gene expression changes behind the above observations we carried out a global transcriptome analysis. We used a pilot DNA microarray hybridization together with extensive RNA sequencing, and confirmed our results by quantitative RT-PCR. Novel functions of the CaPpz1 enzyme and oxidative stress mechanisms have been unraveled. The numbers of genes affected as well as the amplitudes of the transcript level changes indicated that the deletion of the phosphatase sensitized the response of C. albicans to oxidative stress conditions in important physiological functions like membrane transport, cell surface interactions, oxidation-reduction processes, translation and RNA metabolism.

Conclusions: We conclude that in the wild type C. albicans CaPPZ1 has a protective role against oxidative damage. We suggest that the specific inhibition of this phosphatase combined with mild oxidative treatment could be a feasible approach to topical antifungal therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12864-019-6252-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6862791PMC
November 2019

A new, rapid multiplex PCR method identifies frequent probiotic origin among clinical Saccharomyces isolates.

Microbiol Res 2019 Oct 15;227:126298. Epub 2019 Jul 15.

Department of Molecular Biotechnology and Microbiology, University of Debrecen, Egyetem tér 1, Debrecen, H4032, Hungary. Electronic address:

An increasing number of infections originating from probiotic use are reported worldwide, with the majority of such cases caused by the yeast Saccharomyces 'boulardii', a subtype of S. cerevisiae. Reliably linking infectious cases to probiotic products requires unequivocal genotyping data, however, these techniques are often time-consuming and difficult to implement in routine diagnostics. This leads to a widespread lack of genetic data regarding the origin of Saccharomyces infections. We propose a quick and reliable PCR-based protocol for the identification of S. 'boulardii' based on a combined analysis of interdelta fingerprinting and microsatellite typing. By applying various typing methods and our proposed method to the clinical yeast collection of a Hungarian hospital we show that probiotic origin is common among clinical Saccharomyces, and that the new multiplex method enables rapid and unequivocal identification of probiotic yeast infections. This method can be applied for the identification of yeast infection sources, helping decisions on probiotic use.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.micres.2019.126298DOI Listing
October 2019

Physiological and Transcriptional Responses of Candida parapsilosis to Exogenous Tyrosol.

Appl Environ Microbiol 2019 10 1;85(20). Epub 2019 Oct 1.

Department of Medical Microbiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary

Tyrosol plays a key role in fungal morphogenesis and biofilm development. Also, it has a remarkable antifungal effect at supraphysiological concentrations. However, the background of the antifungal effect remains unknown, especially in the case of non- species such as We examined the effect of tyrosol on growth, adhesion, redox homeostasis, virulence, as well as fluconazole susceptibility. To gain further insights into the physiological consequences of tyrosol treatment, we also determined genome-wide gene expression changes using transcriptome sequencing (RNA-Seq). A concentration of 15 mM tyrosol caused significant growth inhibition within 2 h of the addition of tyrosol, while the adhesion of yeast cells was not affected. Tyrosol increased the production of reactive oxygen species remarkably, as revealed by a dichlorofluorescein test, and it was associated with elevated superoxide dismutase, glutathione peroxidase, and catalase activities. The interaction between fluconazole and tyrosol was antagonistic. Tyrosol exposure resulted in 261 and 181 differentially expressed genes with at least a 1.5-fold increase or decrease in expression, respectively, which were selected for further study. Genes involved in ribosome biogenesis showed downregulation, while genes related to the oxidative stress response and ethanol fermentation were upregulated. In addition, tyrosol treatment upregulated the expression of efflux pump genes, including and , and downregulated the expression of the and virulence genes involved in desaturated fatty acid formation. Our data demonstrate that exogenous tyrosol significantly affects the physiology and gene expression of , which could contribute to the development of treatments targeting quorum sensing in the future.-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) are key regulators in fungal physiology, which induce phenotypic adaptations, including morphological changes, altered biofilm formation, and synchronized expression of virulence factors. Moreover, they have a remarkable antifungal activity at supraphysiological concentrations. Limited data are available concerning the tyrosol-induced molecular and physiological effects on non- species such as In addition, the background of the previously observed antifungal effect caused by tyrosol remains unknown. This study reveals that tyrosol exposure enhanced the oxidative stress response and the expression of efflux pump genes, while it inhibited growth and ribosome biogenesis as well as several virulence-related genes. Metabolism was changed toward glycolysis and ethanol fermentation. Furthermore, the initial adherence was not influenced significantly in the presence of tyrosol. Our results provide several potential explanations for the previously observed antifungal effect.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AEM.01388-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805090PMC
October 2019

Tremorgenic and neurotoxic paspaline-derived indole-diterpenes: biosynthetic diversity, threats and applications.

Appl Microbiol Biotechnol 2019 Feb 6;103(4):1599-1616. Epub 2019 Jan 6.

Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

Indole-diterpenes (IDTs) such as the aflatrems, janthitrems, lolitrems, paspalitrems, penitrems, shearinines, sulpinines, and terpendoles are biogenetically related but structurally varied tremorgenic and neurotoxic mycotoxins produced by fungi. All these metabolites derive from the biosynthetic intermediate paspaline, a frequently occurring IDT on its own right. In this comprehensive review, we highlight the similarities and differences of the IDT biosynthetic pathways that lead to the generation of the main paspaline-derived IDT subgroups. We survey the taxonomic distribution and the regulation of IDT production in various fungi and compare the organization of the known IDT biosynthetic gene clusters. A detailed assessment of the highly diverse biological activities of these mycotoxins leads us to emphasize the significant losses that paspaline-derived IDTs cause in agriculture, and compels us to warn about the various hazards they represent towards human and livestock health. Conversely, we also describe the potential utility of these versatile molecules as lead compounds for pharmaceutical drug discovery, and examine the prospects for their industrial scale manufacture in genetically manipulated IDT producers or domesticated host microorganisms in synthetic biological production systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00253-018-09594-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6384164PMC
February 2019

Programmed cell death in human pathogenic fungi - a possible therapeutic target.

Expert Opin Ther Targets 2018 12 30;22(12):1039-1048. Epub 2018 Oct 30.

a Department of Biotechnology and Microbiology , University of Debrecen , Debrecen , Hungary.

Introduction: Diseases caused by pathogenic fungi are increasing because of antibiotic overuse, the rise of immunosuppressive therapies, and climate change. The limited variety of antimycotics and the rapid adaptation of pathogenic fungi to antifungal agents serve to exacerbate this issue. Unfortunately, about 1.6 million people are killed by fungal infections annually. Areas covered: The discovery of the small antimicrobial proteins produced by microorganisms, animals, humans, and plants will hopefully overcome challenges in the treatment of fungal infections. These small proteins are highly stable and any resistance to them rarely evolves; therefore, they are potentially good candidates for the treatment and prevention of infections caused by pathogenic fungi. Some of these proteins target the programmed cell death machinery of pathogenic fungi; this is potentially a novel approach in antimycotic therapies. In this review, we highlight the elements of apoptosis in human pathogenic fungi and related model organisms and discuss the possible therapeutic potential of the apoptosis-inducing, small, antifungal proteins. Expert opinion: Small antimicrobial proteins may establish a new class of antimycotics in the future. The rarity of resistance and their synergistic effects with other frequently used antifungal agents may help pave the way for their use in the clinic.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/14728222.2018.1541087DOI Listing
December 2018

Physiological background of the remarkably high Cd tolerance of the Aspergillus fumigatus Af293 strain.

J Basic Microbiol 2018 Nov 31;58(11):957-967. Epub 2018 Aug 31.

Department of Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Debrecen, Hungary.

The physiological background of the unusually high cadmium tolerance (MIC  > 2 mM) of Aspergillus fumigatus Af293 was investigated. The cadmium tolerance of the tested environmental and clinical A. fumigatus strains varied over a wide range (0.25 mM < MIC  < 1 mM). Only the Af293 strain showed a MIC value of >2 mM, and this phenotype was accompanied by increased in vivo virulence in mice. A strong correlation was found between the cadmium tolerance and the transcription of the pcaA gene, which encodes a putative cadmium efflux pump. The cadmium tolerance also correlated with the iron tolerance and the extracellular siderophore production of the strains. In addition to these findings, Af293 did not show the synergism between iron toxicity and cadmium toxicity that was detected in the other strains. Based on these results, we suggest that the primary function of PcaA should be acting as a ferrous iron pump and protecting cells from iron overload. Nevertheless, the heterologous expression of pcaA may represent an attractive strain improvement strategy to construct fungal strains for use in biosorption or biomining processes or to prevent accumulation of this toxic metal in crops.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jobm.201800200DOI Listing
November 2018

Additional oxidative stress reroutes the global response of Aspergillus fumigatus to iron depletion.

BMC Genomics 2018 May 10;19(1):357. Epub 2018 May 10.

Department of Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Egyetem tér 1, Debrecen, H-4032, Hungary.

Background: Aspergillus fumigatus has to cope with a combination of several stress types while colonizing the human body. A functional interplay between these different stress responses can increase the chances of survival for this opportunistic human pathogen during the invasion of its host. In this study, we shed light on how the HO-induced oxidative stress response depends on the iron available to this filamentous fungus, using transcriptomic analysis, proteomic profiles, and growth assays.

Results: The applied HO treatment, which induced only a negligible stress response in iron-replete cultures, deleteriously affected the fungus under iron deprivation. The majority of stress-induced changes in gene and protein expression was not predictable from data coming from individual stress exposure and was only characteristic for the combination of oxidative stress plus iron deprivation. Our experimental data suggest that the physiological effects of combined stresses and the survival of the fungus highly depend on fragile balances between economization of iron and production of essential iron-containing proteins. One observed strategy was the overproduction of iron-independent antioxidant proteins to combat oxidative stress during iron deprivation, e.g. the upregulation of superoxide dismutase Sod1, the thioredoxin reductase Trr1, and the thioredoxin orthologue Afu5g11320. On the other hand, oxidative stress induction overruled iron deprivation-mediated repression of several genes. In agreement with the gene expression data, growth studies underlined that in A. fumigatus iron deprivation aggravates oxidative stress susceptibility.

Conclusions: Our data demonstrate that studying stress responses under separate single stress conditions is not sufficient to understand how A. fumigatus adapts in a complex and hostile habitat like the human body. The combinatorial stress of iron depletion and hydrogen peroxide caused clear non-additive effects upon the stress response of A. fumigatus. Our data further supported the view that the ability of A. fumigatus to cause diseases in humans strongly depends on its fitness attributes and less on specific virulence factors. In summary, A. fumigatus is able to mount and coordinate complex and efficient responses to combined stresses like iron deprivation plus HO-induced oxidative stress, which are exploited by immune cells to kill fungal pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12864-018-4730-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5946477PMC
May 2018

Heavy Metal-Induced Expression of PcaA Provides Cadmium Tolerance to and Supports Its Virulence in the Model.

Front Microbiol 2018 13;9:744. Epub 2018 Apr 13.

Institute for Microbiology and Genetics, Department of Molecular Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Göttingen, Göttingen, Germany.

Most of the metal transporters in are yet uncharacterized. Their role in fungal metabolism and virulence remains unclear. This paper describes the novel PIB-type cation ATPase PcaA, which links metal homeostasis and heavy metal tolerance in the opportunistic human pathogen . The protein possesses conserved ATPase motif and shares 51% amino acid sequence identity with the cadmium exporter Pca1p. A deletion, an overexpression and a complementation strain of were constructed and their heavy metal susceptibilities were studied. The knock out strain showed drastically decreased cadmium tolerance, however, its growth was not affected by the exposure to high concentrations of copper, iron, zinc, or silver ions. Although the lack of PcaA had no effect on copper adaption, we demonstrated that not only cadmium but also copper ions are able to induce the transcription of in wild type Af293. Similarly, cadmium and copper ions could induce the copper exporting ATPase . These data imply a general response on the transcriptomic level to heavy metals in through the induction of detoxification systems. Confocal microscopy of the complementation strain expressing functional GFP-PcaA supports the predicted membrane localization of PcaA. The GFP-PcaA fusion protein is located in the plasma membrane of in the presence of cadmium ions. Virulence assays support a function of PcaA for virulence of in the wax moth larvae model, which might be linked to the elimination of reactive oxygen species.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2018.00744DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5909057PMC
April 2018