and the Interplay with Amphotericin B: from Resistance to Tolerance?

Aspergillus terreus is an opportunistic causative agent of invasive aspergillosis and, in most cases, it is refractory to amphotericin B (AMB) therapy. Notably, AMB-susceptible Aspergillus terreus (s.s.

The Siderophore Transporters Sit1 and Sit2 Are Essential for Utilization of Ferrichrome-, Ferrioxamine- and Coprogen-Type Siderophores in .

Siderophore-mediated acquisition of iron has been shown to be indispensable for the virulence of several fungal pathogens, the siderophore transporter Sit1 was found to mediate uptake of the novel antifungal drug VL-2397, and siderophores were shown to be useful as biomarkers as well as for imaging of fungal infections. However, siderophore uptake in filamentous fungi is poorly characterized. The opportunistic human pathogen possesses five putative siderophore transporters.

Inducible Selectable Marker Genes to Improve Genetic Manipulation.

The hygromycin B phosphotransferase gene from and the pyrithiamine resistance gene from are two dominant selectable marker genes widely used to genetically manipulate several fungal species. Despite the recent development of CRISPR/Cas9 and marker-free systems, in vitro molecular tools to study  , which is a saprophytic fungus causing life-threatening diseases in immunocompromised hosts, still rely extensively on the use of dominant selectable markers. The limited number of drug selectable markers is already a critical aspect, but the possibility that their introduction into a microorganism could induce enhanced virulence or undesired effects on metabolic behavior constitutes another problem.

Aspergillus terreus Species Complex.

Infections due to species are an acute threat to human health; members of the section are the most frequently occurring agents, but depending on the local epidemiology, representatives of section or section are the second or third most important. species complex is of great interest, as it is usually amphotericin B resistant and displays notable differences in immune interactions in comparison to . The latest epidemiological surveys show an increased incidence of as well as an expanding clinical spectrum (chronic infections) and new groups of at-risk patients being affected.

The Environmental Spread of in Tyrol, Austria.

Fungal infections due to species have become a major cause of morbidity and mortality among immunocompromised patients. At the Medical University of Innsbruck, and related species are the second most common causative agents of aspergillosis. In this one-year study we collected environmental samples to investigate (i) the environmental distribution, (ii) the ecological niche of in Tyrol, (iii) the genetic relatedness of environmental and clinical isolates and the correlation between those two groups of isolates, and (iv) the antifungal susceptibility patterns.

Arginine Auxotrophy Affects Siderophore Biosynthesis and Attenuates Virulence of .

is an opportunistic human pathogen mainly infecting immunocompromised patients. The aim of this study was to characterize the role of arginine biosynthesis in virulence of via genetic inactivation of two key arginine biosynthetic enzymes, the bifunctional acetylglutamate synthase/ornithine acetyltransferase (/AFUA_5G08120) and the ornithine carbamoyltransferase (/AFUA_4G07190). Arginine biosynthesis is intimately linked to the biosynthesis of ornithine, a precursor for siderophore production that has previously been shown to be essential for virulence in .

The leucine biosynthetic pathway is crucial for adaptation to iron starvation and virulence in .

In contrast to mammalia, fungi are able to synthesize the branched-chain amino acid leucine . Recently, the transcription factor LeuB has been shown to cross-regulate leucine biosynthesis, nitrogen metabolism and iron homeostasis in , the most common human mold pathogen. Moreover, the leucine biosynthetic pathway intermediate α-isopropylmalate (α-IPM) has previously been shown to posttranslationally activate LeuB homologs in and .

The Siderophore Transporter Sit1 Determines Susceptibility to the Antifungal VL-2397.

VL-2397 (previously termed ASP2397) is an antifungal, aluminum-chelating cyclic hexapeptide with a structure analogous to that of ferrichrome-type siderophores, whereby replacement of aluminum by iron was shown to decrease the antifungal activity of this compound. Here, we found that inactivation of an importer for ferrichrome-type siderophores, termed Sit1, renders resistant to VL-2397. Moreover, expression of the endogenous gene under the control of a xylose-inducible promoter (to uncouple expression from iron repression) combined with C-terminal tagging with a fluorescent protein demonstrated localization of Sit1 in the plasma membrane and xylose-dependent VL-2397 susceptibility.

Intermicrobial interaction: Aspergillus fumigatus siderophores protect against competition by Pseudomonas aeruginosa.

Pseudomonas aeruginosa and Aspergillus fumigatus are pathogens frequently co-inhabiting immunocompromised patient airways, particularly in people with cystic fibrosis. Both microbes depend on the availability of iron, and compete for iron in their microenvironment. We showed previously that the P.

Aspergillus-Pseudomonas interaction, relevant to competition in airways.

In airways of immunocompromised patients and individuals with cystic fibrosis, Pseudomonas aeruginosa and Aspergillus fumigatus are the most common opportunistic bacterial and fungal pathogens. Both pathogens form biofilms and cause acute and chronic illnesses. Previous studies revealed that P.

Siroheme Is Essential for Assimilation of Nitrate and Sulfate as Well as Detoxification of Nitric Oxide but Dispensable for Murine Virulence of .

The saprophytic mold is the most common airborne fungal pathogen causing severe invasive fungal infections in immunocompromised patients. Siroheme is a heme-like prosthetic group used by plants and microorganisms for sulfate and nitrate assimilation but is absent in higher eukaryotes. Here, we investigated the role of siroheme in by deletion of the gene encoding the bifunctional dehydrogenase/ferrochelatase enzyme Met8.

Human MAIT cells are rapidly activated by Aspergillus spp. in an APC-dependent manner.

Mucosal associated invariant T cells (MAIT cells) are innate-like T cells (TC) which are known to be activated by several bacteria and viruses. However, activation of MAIT cells by moulds, such as the opportunistic human pathogen Aspergillus, is not well described. Stimulation of human PBMC with A.

Riboflavin and pantothenic acid biosynthesis are crucial for iron homeostasis and virulence in the pathogenic mold Aspergillus fumigatus.

Background: Aspergillus fumigatus is the most prevalent airborne fungal pathogen, causing invasive fungal infections mainly in immunosuppressed individuals. Death rates from invasive aspergillosis remain high because of limited treatment options and increasing antifungal resistance. The aim of this study was to identify key fungal-specific genes participating in vitamin B biosynthesis in A.

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

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.

Studies of Pseudomonas aeruginosa Mutants Indicate Pyoverdine as the Central Factor in Inhibition of Aspergillus fumigatus Biofilm.

and are common opportunistic bacterial and fungal pathogens, respectively. They often coexist in airways of immunocompromised patients and individuals with cystic fibrosis, where they form biofilms and cause acute and chronic illnesses. Hence, the interactions between them have long been of interest and it is known that can inhibit We have approached the definition of the inhibitory molecules by studying 24 mutants with various virulence genes deleted for the ability to inhibit biofilms.

Systematic Identification of Anti-Fungal Drug Targets by a Metabolic Network Approach.

New antimycotic drugs are challenging to find, as potential target proteins may have close human orthologs. We here focus on identifying metabolic targets that are critical for fungal growth and have minimal similarity to targets among human proteins. We compare and combine here: (I) direct metabolic network modeling using elementary mode analysis and flux estimates approximations using expression data, (II) targeting metabolic genes by transcriptome analysis of condition-specific highly expressed enzymes, and (III) analysis of enzyme structure, enzyme interconnectedness ("hubs"), and identification of pathogen-specific enzymes using orthology relations.

Histidine biosynthesis plays a crucial role in metal homeostasis and virulence of Aspergillus fumigatus.

Aspergillus fumigatus is the most prevalent airborne fungal pathogen causing invasive fungal infections in immunosuppressed individuals. The histidine biosynthetic pathway is found in bacteria, archaebacteria, lower eukaryotes, and plants, but is absent in mammals. Here we demonstrate that deletion of the gene encoding imidazoleglycerol-phosphate dehydratase (HisB) in A.

Identification and characterization of haemofungin, a novel antifungal compound that inhibits the final step of haem biosynthesis.

Objectives: During recent decades, the number of invasive fungal infections among immunosuppressed patients has increased significantly, whereas the number of effective systemic antifungal drugs remains low and unsatisfactory. The aim of this study was to characterize a novel antifungal compound, CW-8/haemofungin, which we previously identified in a screen for compounds affecting fungal cell wall integrity.

Methods: The in vitro characteristics of haemofungin were investigated by MIC evaluation against a panel of pathogenic and non-pathogenic fungi, bacteria and mammalian cells in culture.