scholarly journals Candida albicans Uses Multiple Mechanisms To Acquire the Essential Metabolite Inositol during Infection

2008 ◽  
Vol 76 (6) ◽  
pp. 2793-2801 ◽  
Author(s):  
Ying-Lien Chen ◽  
Sarah Kauffman ◽  
Todd B. Reynolds
Keyword(s):  
Candida Albicans ◽  
Mouse Model ◽  
Double Mutant ◽  
De Novo ◽  
Systemic Infection ◽  
Bloodstream Infections ◽  
Wild Type Allele ◽  
Transporter Gene ◽  
Wild Type ◽  
Life Threatening

ABSTRACT Candida albicans is an important cause of life-threatening systemic bloodstream infections in immunocompromised patients. In order to cause infections, C. albicans must be able to synthesize the essential metabolite inositol or acquire it from the host. Based on the similarity of C. albicans to Saccharomyces cerevisiae, it was predicted that C. albicans may generate inositol de novo, import it from the environment, or both. The C. albicans inositol synthesis gene INO1 (orf19.7585) and inositol transporter gene ITR1 (orf19.3526) were each disrupted. The ino1Δ/ino1Δ mutant was an inositol auxotroph, and the itr1Δ/itr1Δ mutant was unable to import inositol from the medium. Each of these mutants was fully virulent in a mouse model of systemic infection. It was not possible to generate an ino1Δ/ino1Δ itr1Δ/itr1Δ double mutant, suggesting that in the absence of these two genes, C. albicans could not acquire inositol and was nonviable. A conditional double mutant was created by replacing the remaining wild-type allele of ITR1 in an ino1Δ/ino1Δ itr1Δ/ITR1 strain with a conditionally expressed allele of ITR1 driven by the repressible MET3 promoter. The resulting ino1Δ/ino1Δ itr1Δ/PMET3 ::ITR1 strain was found to be nonviable in medium containing methionine and cysteine (which represses the PMET3 promoter), and it was avirulent in the mouse model of systemic candidiasis. These results suggest a model in which C. albicans has two equally effective mechanisms for obtaining inositol while in the host. It can either generate inositol de novo through Ino1p, or it can import it from the host through Itr1p.

scholarly journals Combined Inactivation of the Candida albicans GPR1 and TPS2 Genes Results in Avirulence in a Mouse Model for Systemic Infection

2008 ◽  
Vol 76 (4) ◽  
pp. 1686-1694 ◽  
Author(s):  
Mykola M. Maidan ◽  
Larissa De Rop ◽  
Miguel Relloso ◽  
Rosalia Diez-Orejas ◽  
Johan M. Thevelein ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Mouse Model ◽  
Double Mutant ◽  
Systemic Infection ◽  
Antifungal Drugs ◽  
The Other ◽  
Growth Defect ◽  
Other Hand ◽  
Solid Media

ABSTRACT Inhibition of the biosynthesis of trehalose, a well-known stress protectant in pathogens, is an interesting approach for antifungal or antibacterial therapy. Deletion of TPS2, encoding trehalose-6-phosphate (T6P) phosphatase, results in strongly reduced virulence of Candida albicans due to accumulation of T6P instead of trehalose in response to stress. To further aggravate the deregulation in the pathogen, we have additionally deleted the GPR1 gene, encoding the nutrient receptor that activates the cyclic AMP-protein kinase A signaling pathway, which negatively regulates trehalose accumulation in yeasts. A gpr1 mutant is strongly affected in morphogenesis on solid media as well as in vivo in a mouse model but has only a slightly decreased virulence. The gpr1 tps2 double mutant, on the other hand, is completely avirulent in a mouse model for systemic infection. This strain accumulates very high T6P levels under stress conditions and has a growth defect at higher temperatures. We also show that a tps2 mutant is more sensitive to being killed by macrophages than the wild type or the gpr1 mutant. A double mutant has susceptibility similar to that of the single tps2 mutant. For morphogenesis on solid media, on the other hand, the gpr1 tps2 mutant shows a phenotype similar to that of the single gpr1 mutant. Taken together these results show that there is synergism between Gpr1 and Tps2 and that their combined inactivation results in complete avirulence. Combination therapy targeting both proteins may prove highly effective against pathogenic fungi with increased resistance to the currently used antifungal drugs.

scholarly journals The Early Transcriptional Response of Human Granulocytes to Infection with Candida albicans Is Not Essential for Killing but Reflects Cellular Communications

2006 ◽  
Vol 75 (3) ◽  
pp. 1493-1501 ◽  
Author(s):  
Chantal Fradin ◽  
Abigail L. Mavor ◽  
Günther Weindl ◽  
Martin Schaller ◽  
Karin Hanke ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Mononuclear Cells ◽  
De Novo ◽  
Transcriptional Response ◽  
Mononuclear Leukocytes ◽  
General Notion ◽  
Genes Encoding ◽  
Global Transcriptional Profile ◽  
Life Threatening ◽  
Systemic Infections

ABSTRACT Candida albicans is a polymorphic opportunistic fungus that can cause life-threatening systemic infections following hematogenous dissemination in patients susceptible to nosocomial infection. Neutrophils form part of the innate immune response, which is the first line of defense against microbes and is particularly important in C. albicans infections. To compare the transcriptional response of leukocytes exposed to C. albicans, we investigated the expression of key cytokine genes in polymorphonuclear and mononuclear leukocytes after incubation with C. albicans for 1 h. Isolated mononuclear cells expressed high levels of genes encoding proinflammatory signaling molecules, whereas neutrophils exhibited much lower levels, similar to those observed in whole blood. The global transcriptional profile of neutrophils was examined by using an immunology-biased human microarray to determine whether different morphological forms or the viability of C. albicans altered the transcriptome. Hyphal cells appeared to have the broadest effect, although the most strongly induced genes were regulated independently of morphology or viability. These genes were involved in proinflammatory cell-cell signaling, cell signal transduction, and cell growth. Generally, genes encoding known components of neutrophil granules showed no upregulation at this time point; however, lactoferrin, a well-known candidacidal peptide, was secreted by neutrophils. Addition to inhibitors of RNA or protein de novo synthesis did not influence the killing activity within 30 min. These results support the general notion that neutrophils do not require gene transcription to mount an immediate and direct attack against microbes. However, neutrophils exposed to C. albicans express genes involved in communication with other immune cells.

scholarly journals De Novo Development of mtDNA Deletion Due to Decreased POLG and SSBP1 Expression in Humans

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 284
Author(s):  
Yeonmi Lee ◽  
Taeho Kim ◽  
Miju Lee ◽  
Seongjun So ◽  
Mustafa Zafer Karagozlu ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
De Novo ◽  
Wild Type Allele ◽  
Wild Type ◽  
Factors Associated ◽  
Mtdna Deletions ◽  
Nuclear Factors ◽  
Mtdna Deletion ◽  
In The Wild ◽  
Mtdna Replication

Defects in the mitochondrial genome (mitochondrial DNA (mtDNA)) are associated with both congenital and acquired disorders in humans. Nuclear-encoded DNA polymerase subunit gamma (POLG) plays an important role in mtDNA replication, and proofreading and mutations in POLG have been linked with increased mtDNA deletions. SSBP1 is also a crucial gene for mtDNA replication. Here, we describe a patient diagnosed with Pearson syndrome with large mtDNA deletions that were not detected in the somatic cells of the mother. Exome sequencing was used to evaluate the nuclear factors associated with the patient and his family, which revealed a paternal POLG mutation (c.868C > T) and a maternal SSBP1 mutation (c.320G > A). The patient showed lower POLG and SSBP1 expression than his healthy brothers and the general population of a similar age. Notably, c.868C in the wild-type allele was highly methylated in the patient compared to the same site in both his healthy brothers. These results suggest that the co- deficient expression of POLG and SSBP1 genes could contribute to the development of mtDNA deletion.

scholarly journals The Meningococcal ABC-Type l-Glutamate Transporter GltT Is Necessary for the Development of Experimental Meningitis in Mice

2009 ◽  
Vol 77 (9) ◽  
pp. 3578-3587 ◽  
Author(s):  
Roberta Colicchio ◽  
Susanna Ricci ◽  
Florentia Lamberti ◽  
Caterina Pagliarulo ◽  
Chiara Pagliuca ◽  
...  
Keyword(s):  
Histological Analysis ◽  
Glutamate Uptake ◽  
Glutamate Transporter ◽  
Systemic Infection ◽  
Fold Increase ◽  
Wild Type ◽  
Nutrient Source ◽  
Infectious Dose ◽  
Life Threatening ◽  
The Brain

ABSTRACT Experimental animal models of bacterial meningitis are useful to study the host-pathogen interactions occurring at the cerebral level and to analyze the pathogenetic mechanisms behind this life-threatening disease. In this study, we have developed a mouse model of meningococcal meningitis based on the intracisternal inoculation of bacteria. Experiments were performed with mouse-passaged serogroup C Neisseria meningitidis. Survival and clinical parameters of infected mice and microbiological and histological analysis of the brain demonstrated the establishment of meningitis with features comparable to those of the disease in humans. When using low bacterial inocula, meningococcal replication in the brain was very efficient, with a 1,000-fold increase of viable counts in 18 h. Meningococci were also found in the blood, spleens, and livers of infected mice, and bacterial loads in different organs were dependent on the infectious dose. As glutamate uptake from the host has been implicated in meningococcal virulence, mice were infected intracisternally with an isogenic strain deficient in the ABC-type l-glutamate transporter GltT. Noticeably, the mutant was attenuated in virulence in mixed infections, indicating that wild-type bacteria outcompeted the GltT-deficient meningococci. The data show that the GltT transporter plays a role in meningitis and concomitant systemic infection, suggesting that meningococci may use l-glutamate as a nutrient source and as a precursor to synthesize the antioxidant glutathione.

scholarly journals Candida albicans Lacking the Gene Encoding the Regulatory Subunit of Protein Kinase A Displays a Defect in Hyphal Formation and an Altered Localization of the Catalytic Subunit

2004 ◽  
Vol 3 (1) ◽  
pp. 190-199 ◽  
Author(s):  
Alejandro Cassola ◽  
Marc Parrot ◽  
Susana Silberstein ◽  
Beatrice B. Magee ◽  
Susana Passeron ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Protein Kinase ◽  
Fusion Protein ◽  
Protein Kinase A ◽  
Double Mutant ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Wild Type ◽  
Gfp Fusion Protein ◽  
Kinase A

ABSTRACT The fungal pathogen Candida albicans switches from a yeast-like to a filamentous mode of growth in response to a variety of environmental conditions. We examined the morphogenetic behavior of C. albicans yeast cells lacking the BCY1 gene, which encodes the regulatory subunit of protein kinase A. We cloned the BCY1 gene and generated a bcy1 tpk2 double mutant strain because a homozygous bcy1 mutant in a wild-type genetic background could not be obtained. In the bcy1 tpk2 mutant, protein kinase A activity (due to the presence of the TPK1 gene) was cyclic AMP independent, indicating that the cells harbored an unregulated phosphotransferase activity. This mutant has constitutive protein kinase A activity and displayed a defective germinative phenotype in N-acetylglucosamine and in serum-containing medium. The subcellular localization of a Tpk1-green fluorescent protein (GFP) fusion protein was examined in wild-type, tpk2 null, and bcy1 tpk2 double mutant strains. The fusion protein was observed to be predominantly nuclear in wild-type and tpk2 strains. This was not the case in the bcy1 tpk2 double mutant, where it appeared dispersed throughout the cell. Coimmunoprecipitation of Bcy1p with the Tpk1-GFP fusion protein demonstrated the interaction of these proteins inside the cell. These results suggest that one of the roles of Bcy1p is to tether the protein kinase A catalytic subunit to the nucleus.

scholarly journals REGULATION OF PHOSPHATE METABOLISM IN NEUROSPORA CRASSA. CHARACTERIZATION OF REGULATORY MUTANTS

Genetics ◽  
1973 ◽  
Vol 75 (1) ◽  
pp. 61-73
Author(s):  
John F Lehman ◽  
Mary K Gleason ◽  
Sandra K Ahlgren ◽  
Robert L Metzenberg
Keyword(s):  
Alkaline Phosphatase ◽  
Neurospora Crassa ◽  
Control Systems ◽  
Double Mutant ◽  
Phosphorus Metabolism ◽  
Phosphate Metabolism ◽  
Wild Type Allele ◽  
Wild Type ◽  
High Affinity

ABSTRACT A mutant of Neurospora crassa, called UW-6, differs from wild type in being partially constitutive for synthesis of a species of alkaline phosphatase, and also for a species of phosphate permease that has a high affinity for phosphate at high pH. UW-6 is possibly allelic with a mutant called nuc-2 that was previously isolated by Ishikawa. nuc-2 has the converse phenotype, in that it cannot be derepressed for either of these two activities. UW-6 is co-dominant with its wild-type allele in heterokaryons and in partial diploids. An unlinked mutant, nuc-1, is like nuc-2 in that it fails to make the alkaline phosphatase or the permease referred to above. nuc-1 is epistatic to UW-6 in the double mutant. The control of phosphorus metabolism is discussed, and is compared with some other control systems in filamentous fungi.

scholarly journals Phased diploid genome assemblies for three strains of Candida albicans from oak trees

2019 ◽  
Author(s):  
Jennafer A. P. Hamlin ◽  
Guilherme Dias ◽  
Casey M. Bergman ◽  
Douda Bensasson
Keyword(s):  
Candida Albicans ◽  
De Novo ◽  
Bloodstream Infections ◽  
Genomic Variation ◽  
High Rate ◽  
The United Kingdom ◽  
Oak Trees ◽  
Wide Range ◽  
Animal Hosts ◽  
Genome Assemblies

ABSTRACTAlthough normally a harmless commensal, Candida albicans has the potential to generate a wide range of infections including systemic candidaemia, making it the most common cause of bloodstream infections worldwide with a high rate of mortality. C. albicans has long been considered an obligate commensal, however, recent studies suggest it can live outside animal hosts. Here, we have generated PacBio sequencing and phased genome assemblies for three C. albicans strains from oak trees in the United Kingdom (NCYC 4144, NCYC 4145, and NCYC 4146). Our results provide phased de novo diploid assemblies for C. albicans and provide a framework to study patterns of genomic variation within and among strains of an important fungal pathogen.

scholarly journals Systematic truncations of chromosome 4 and their responses to antifungals in Candida albicans

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Wasim Uddin ◽  
Darshan Dhabalia ◽  
S. M. Udaya Prakash ◽  
M. Anaul Kabir
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Resistant Mutant ◽  
Wild Type ◽  
Human Fungal Pathogen ◽  
Zones Of Inhibition ◽  
Life Threatening ◽  
Fluconazole Resistant ◽  
Diffusion Assay ◽  
Type Strains

Abstract Background Candida albicans is an opportunistic human fungal pathogen responsible for superficial and systemic life-threatening infections. Treating these infections is challenging as many clinical isolates show increased drug resistance to antifungals. Chromosome (Chr) 4 monosomy was implicated in a fluconazole-resistant mutant. However, exposure to fluconazole adversely affects Candida cells and can generate numerous mutations. Hence, the present study aimed to truncate Chr4 and challenge the generated Candida strains to antifungals and evaluate their role in drug response. Results Herein, Chr4 was truncated in C. albicans using the telomere-mediated chromosomal truncation method. The resulting eight Candida strains carrying one truncated homolog of Chr4 were tested for response to multiple antifungals. The minimal inhibitory concentration (MIC) for these strains was determined against three classes of antifungals. The MIC values against fluconazole, amphotericin B, and caspofungin were closer to that of the wild type strain. Microdilution assay against fluconazole showed that the mutants and wild type strains had similar sensitivity to fluconazole. The disc diffusion assay against five azoles and two polyenes revealed that the zones of inhibition for all the eight strains were similar to those of the wild type. Thus, none of the generated strains showed any significant resistance to the tested antifungals. However, spot assay exhibited a reasonably high tolerance of a few generated strains with increasing concentrations of fluconazole. Conclusion This analysis suggested that Chr4 aneuploidy might not underlie drug resistance but rather drug tolerance in Candida albicans.

scholarly journals Candida albicans Killing by RAW 264.7 Mouse Macrophage Cells: Effects of Candida Genotype, Infection Ratios, and Gamma Interferon Treatment

2002 ◽  
Vol 70 (11) ◽  
pp. 6319-6329 ◽  
Author(s):  
A. Marcil ◽  
D. Harcus ◽  
D. Y. Thomas ◽  
M. Whiteway
Keyword(s):  
Candida Albicans ◽  
Cell Line ◽  
Systemic Infection ◽  
Gamma Interferon ◽  
Raw 264.7 ◽  
Mouse Macrophage ◽  
Wild Type ◽  
Macrophage Cells ◽  
Dilution Assay ◽  
Infection Models

ABSTRACT Phagocytic cells such as neutrophils and macrophages are potential components of the immune defense that protects mammals against Candida albicans infection. We have tested the interaction between the mouse macrophage cell line RAW 264.7 and a variety of mutant strains of C. albicans. We used an end point dilution assay to monitor the killing of C. albicans at low multiplicities of infection (MOIs). Several mutants that show reduced virulence in mouse systemic-infection models show reduced colony formation in the presence of macrophage cells. To permit analysis of the macrophage-Candida interaction at higher MOIs, we introduced a luciferase reporter gene into wild-type and mutant Candida cells and used loss of the luminescence signal to quantify proliferation. This assay gave results similar to those for the end point dilution assay. Activation of the macrophages with mouse gamma interferon did not enhance anti-Candida activity. Continued coculture of the Candida and macrophage cells eventually led to death of the macrophages, but for the RAW 264.7 cell line this was not due to apoptotic pathways involving caspase-8 or -9 activation. In general Candida cells defective in the formation of hyphae were both less virulent in animal models and more sensitive to macrophage engulfment and growth inhibition. However the nonvirulent, hypha-defective cla4 mutant line was considerably more resistant to macrophage-mediated inhibition than the wild-type strain. Thus although mutants sensitive to engulfment are typically less virulent in systemic-infection models, sensitivity to phagocytic macrophage cells is not the unique determinant of C. albicans virulence.

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