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Wild-type Drosophila melanogaster as a model host to analyze nitrogen source dependent virulence of Candida albicans.

ABSTRACT: The fungal pathogen Candida albicans is a common cause of opportunistic infections in humans. We report that wild-type Drosophila melanogaster (OrR) flies are susceptible to virulent C. albicans infections and have established experimental conditions that enable OrR flies to serve as model hosts for studying C. albicans virulence. After injection into the thorax, wild-type C. albicans cells disseminate and invade tissues throughout the fly, leading to lethality. Similar to results obtained monitoring systemic infections in mice, well-characterized cph1? efg1? and csh3? fungal mutants exhibit attenuated virulence in flies. Using the OrR fly host model, we assessed the virulence of C. albicans strains individually lacking functional components of the SPS sensing pathway. In response to extracellular amino acids, the plasma membrane localized SPS-sensor (Ssy1, Ptr3, and Ssy5) activates two transcription factors (Stp1 and Stp2) to differentially control two distinct modes of nitrogen acquisition (host protein catabolism and amino acid uptake, respectively). Our results indicate that a functional SPS-sensor and Stp1 controlled genes required for host protein catabolism and utilization, including the major secreted aspartyl protease SAP2, are required to establish virulent infections. By contrast, Stp2, which activates genes required for amino acid uptake, is dispensable for virulence. These results indicate that nutrient availability within infected hosts directly influences C. albicans virulence.

SUBMITTER: Davis MM

PROVIDER: S-EPMC3215725 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Wild-type Drosophila melanogaster as a model host to analyze nitrogen source dependent virulence of Candida albicans.

Davis Monica M MM Alvarez Francisco J FJ Ryman Kicki K Holm Åsa A ÅA Ljungdahl Per O PO Engström Ylva Y

PloS one 20111114 11

The fungal pathogen Candida albicans is a common cause of opportunistic infections in humans. We report that wild-type Drosophila melanogaster (OrR) flies are susceptible to virulent C. albicans infections and have established experimental conditions that enable OrR flies to serve as model hosts for studying C. albicans virulence. After injection into the thorax, wild-type C. albicans cells disseminate and invade tissues throughout the fly, leading to lethality. Similar to results obtained monit ...[more]

PMID: 22110651

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Project description:UnlabelledCandida albicans is the most prevalent fungal pathogen of humans, causing a variety of diseases ranging from superficial mucosal infections to deep-seated systemic invasions. Mucus, the gel that coats all wet epithelial surfaces, accommodates C. albicans as part of the normal microbiota, where C. albicans resides asymptomatically in healthy humans. Through a series of in vitro experiments combined with gene expression analysis, we show that mucin biopolymers, the main gel-forming constituents of mucus, induce a new oval-shaped morphology in C. albicans in which a range of genes related to adhesion, filamentation, and biofilm formation are downregulated. We also show that corresponding traits are suppressed, rendering C. albicans impaired in forming biofilms on a range of different synthetic surfaces and human epithelial cells. Our data suggest that mucins can manipulate C. albicans physiology, and we hypothesize that they are key environmental signals for retaining C. albicans in the host-compatible, commensal state.ImportanceThe yeast Candida albicans causes both superficial infections of the mucosa and life-threatening infections upon entering the bloodstream. However, C. albicans is not always harmful and can exist as part of the normal microbiota without causing disease. Internal body surfaces that are susceptible to infection by C. albicans are coated with mucus, which we hypothesize plays an important role in preventing infections. Here, we show that the main components of mucus, mucin glycoproteins, suppress virulence attributes of C. albicans at the levels of gene expression and the corresponding morphological traits. Specifically, mucins suppress attachment to plastic surfaces and human cells, the transition to cell-penetrating hyphae, and the formation of biofilms (drug-resistant microbial communities). Additionally, exposure to mucins induces an elongated morphology that physically resembles the mating-competent opaque state but is phenotypically distinct. We suggest that mucins are potent antivirulence molecules that have therapeutic potential for suppressing C. albicans infections.

Project description:The dimorphic fungus Candida albicans is one of the most important opportunistic pathogens for humankind. The use of fungicides against Candida could be associated with sub-inhibitory effects, which are referred to as fungal stress responses and are undesirable for the host. In this work, we investigated the antifungal action of 2,4-diacetylphloroglucinol (2,4-DAPG) against Candida albicans ATCC 10231 with a focus on their biofilm-forming ability. We found that 2,4-DAPG was able to reduce the ability of Candida cells to form biofilms, but complete inhibition and eradication effects were not achieved. Furthermore, C. albicans cells in the adherent state were characterized by reduced susceptibility to 2,4-DAPG compared to planktonic cells. The investigation of the mechanisms that could explain the antibiofilm action of 2,4-DAPG revealed a reduction in the cell`s surface hydrophobicity and the inhibition of the yeast-to-hyphae transition. The inhibition of the Candida cells filamentation was accompanied by an increase in the expression of the NRG1 gene, which is a negative regulator of hyphal development. In addition, we microscopically visualized the treated biofilms and revealed numerous channels that were decorated with particles and localized on the hyphae. We assumed that these hyphal structures could be associated with the secretion of aspartyl proteases (Sap). The performed assessments revealed an increase in the activity of Sap, which was accompanied by an increase in the expression of the sap2 and sap4 genes. The antifungal action of 2,4-DAPG is known to be associated with affecting the permeability of cellular structures, which leads to H+ATPase malfunction and the disruption of mitochondrial respiration. The subsequent cytosol acidification and generation of ROS trigger the inhibition of Candida filamentation and activation of Sap production. The introduction of antioxidant Trolox simultaneously with 2,4-DAPG leads to a reduction in Sap production. Collectively, the obtained data indicate new aspects of the interaction of fungal cells with 2,4-DAPG, an antimicrobial metabolite of Pseudomonas spp.

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Wild-type Drosophila melanogaster as a model host to analyze nitrogen source dependent virulence of Candida albicans.

Publications

Wild-type Drosophila melanogaster as a model host to analyze nitrogen source dependent virulence of Candida albicans.

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