Characterization and functional analysis of zinc trafficking in the human fungal pathogen Candida parapsilosis

The zinc restriction and zinc toxicity are part of host defence, called nutritional immunity. The crucial role of zinc homeostasis in microbial survival within a host is established, but little is known about these processes in the opportunistic human fungal pathogen Candida parapsilosis. Our in silico predictions suggested the presence of at least six potential zinc transporters (ZnTs) in C. parapsilosis-orthologues of ZRC1, ZRT3 and ZRT101-but an orthologue of PRA1 zincophore was not found. In addition, we detected a species-specific gene expansion of the novel ZnT ZRT2, as we identified three orthologue genes in the genome of C. parapsilosis. Based on predictions, we created homozygous mutant strains of the potential ZnTs and characterized them. Despite the apparent gene expansion of ZRT2 in C. parapsilosis, only CpZRT21 was essential for growth in a zinc-depleted acidic environment, in addition we found that CpZrc1 is essential for zinc detoxification and also protects the fungi against the elimination of murine macrophages. Significantly, we demonstrated that C. parapsilosis forms zincosomes in a Zrc1-independent manner and zinc detoxification is mediated by the vacuolar importer CpZrc1. Our study defines the functions of C. parapsilosis ZnTs, including a species-specific survival and zinc detoxification system

A Candida parapsilosis Overexpression Collection Reveals Genes Required for Pathogenesis

Relative to the vast data regarding the virulence mechanisms of Candida albicans, there is limited knowledge on the emerging opportunistic human pathogen Candida parapsilosis. The aim of this study was to generate and characterize an overexpression mutant collection to identify and explore virulence factors in C. parapsilosis. With the obtained mutants, we investigated stress tolerance, morphology switch, biofilm formation, phagocytosis, and in vivo virulence in Galleria mellonella larvae and mouse models. In order to evaluate the results, we compared the data from the C. parapsilosis overexpression collection analysis to the results derived from previous deletion mutant library characterizations. Of the 37 overexpression C. parapsilosis mutants, we identified eight with altered phenotypes compared to the controls. This work is the first report to identify CPAR2_107240, CPAR2_108840, CPAR2_302400, CPAR2_406400, and CPAR2_602820 as contributors to C. parapsilosis virulence by regulating functions associated with host-pathogen interactions and biofilm formation. Our findings also confirmed the role of CPAR2_109520, CPAR2_200040, and CPAR2_500180 in pathogenesis. This study was the first attempt to use an overexpression strategy to systematically assess gene function in C. parapsilosis, and our results demonstrate that this approach is effective for such investigations

Recrystallization-induced oxygen isotope changes in inclusion-hosted water of speleothems - Paleoclimatological implications

The issue of diagenetic alteration of carbonate deposits in caves (speleothems) has gained increasing importance in recent years, as this process has serious consequences for speleothem-based paleoclimate studies. In this study stable hydrogen and oxygen isotope data of water trapped in fluid inclusions were collected for recently forming stalagmites and flowstones in order to determine how dripwater compositions are reflected and preserved in the inclusion water compositions. Hydrogen isotope compositions were found to reflect dripwater values, whereas the oxygen isotope data were increasingly shifted from the local dripwater compositions with the time elapsed after deposition. The δ18O data are correlated with X-Ray diffraction full width at half maximum values (related to crystal domain size and lattice strain), suggesting that the oxygen isotope shift is related to recrystallization of calcite. Transmission electron microscope analyses detected the presence of nanocrystalline (200 nm) may have induced re-equilibration between the carbonate and the trapped inclusion water. The Ostwald ripening process provides an explanation for unexpectedly low oxygen isotope compositions in the inclusion water. The detected diagenetic alteration and its isotopic effects should be taken into consideration during sampling strategies and data evaluation as speleothems containing nanocrystalline calcite during their deposition are prone to late-stage oxygen isotope water-carbonate re-equilibration, which may shift the oxygen isotope composition of the inclusion water to more depleted values while the hydrogen isotope composition remains intact. © 2016

Keratitis caused by the recently described new species Aspergillus brasiliensis: two case reports

<p>Abstract</p> <p>Introduction</p> <p>Human infections caused by <it>Aspergillus brasiliensis </it>have not yet been reported. We describe the first two known cases of fungal keratitis caused by <it>Aspergillus brasiliensis</it>.</p> <p>Case presentations</p> <p>A 49-year-old Indian Tamil woman agricultural worker came with pain and defective vision in the right eye for one month. Meanwhile, a 35-year-old Indian Tamil woman presented with a history of a corneal ulcer involving the left eye for 15 days. The fungal strains isolated from these two cases were originally suspected to belong to <it>Aspergillus </it>section <it>Nigri </it>based on macro- and micromorphological characteristics. Molecular identification revealed that both isolates represent <it>A. brasiliensis</it>.</p> <p>Conclusion</p> <p>The two <it>A. brasiliensis </it>strains examined in this study were part of six keratitis isolates from <it>Aspergillus </it>section <it>Nigri</it>, suggesting that this recently described species may be responsible for a significant proportion of corneal infections caused by black Aspergilli. The presented cases also indicate that significant differences may occur between the severities of keratitis caused by individual isolates of <it>A. brasiliensis</it>.</p

Melanoma-Derived Exosomes Induce PD-1 Overexpression and Tumor Progression via Mesenchymal Stem Cell Oncogenic Reprogramming

Recently, it has been described that programmed cell death protein 1 (PD-1) overexpressing melanoma cells are highly aggressive. However, until now it has not been defined which factors lead to the generation of PD-1 overexpressing subpopulations. Here, we present that melanoma-derived exosomes, conveying oncogenic molecular reprogramming, induce the formation of a melanoma-like, PD-1 overexpressing cell population (mMSCPD-1+) from naïve mesenchymal stem cells (MSCs). Exosomes and mMSCPD-1+ cells induce tumor progression and expression of oncogenic factors in vivo. Finally, we revealed a characteristic, tumorigenic signaling network combining the upregulated molecules (e.g., PD-1, MET, RAF1, BCL2, MTOR) and their upstream exosomal regulating proteins and miRNAs. Our study highlights the complexity of exosomal communication during tumor progression and contributes to the detailed understanding of metastatic processes