Identification of the dialysable serum inducer of germ-tube formation in Candida albicans

Yeast cells of Candida albicans are induced by serum at 37 °C to produce germ tubes, the first step in a transition from yeast to hyphal growth. Previously, it has been shown that the active component is not serum albumin but is present in the dialysable fraction of serum. In this study, serum induction of germ-tube formation is shown to occur even in the presence of added exogenous nitrogen sources and is therefore not signalled by nitrogen derepression. The active component in serum was purified by ion-exchange, reverse-phase and size-exclusion chromatography from the dialysable fraction of serum and was identified by NMR to be d-glucose. Enzymic destruction of glucose, using glucose oxidase, demonstrated that d-glucose was the only active component in these fractions. Induction of germ-tube formation by d-glucose required a temperature of 37 °C and the pH optimum was between pH 7·0 and 8·0. d-Glucose induced germ-tube formation in a panel of clinical isolates of C. albicans. Although d-glucose is the major inducer in serum, a second non-dialysable, trichloroacetic acid precipitable inducer is also present. However, whereas either 1·4 % (v/v) serum or an equivalent concentration of d-glucose induced 50 % germ-tube formation, the non-dialysable component required a 10-fold higher concentration to induce 50 % germ-tube formation. Serum is, therefore, the most effective induction medium for germ-tube formation because it is buffered at about pH 8·5 and contains two distinct inducers (glucose and a non-dialysable component), both active at this pH.

Download Full-text

A putative dual-specific protein phosphatase encoded by YVH1 controls growth, filamentation and virulence in Candida albicans

Microbiology ◽

10.1099/mic.0.27999-0 ◽

2005 ◽

Vol 151 (7) ◽

pp. 2223-2232 ◽

Cited By ~ 23

Author(s):

Nozomu Hanaoka ◽

Takashi Umeyama ◽

Keigo Ueno ◽

Kenji Ueda ◽

Teruhiko Beppu ◽

...

Keyword(s):

Cell Cycle ◽

Candida Albicans ◽

Cell Cycle Progression ◽

Germ Tube ◽

Hyphal Growth ◽

Tube Formation ◽

Yeast Cells ◽

Nucleotide Polymorphisms ◽

Wild Type ◽

Cycle Progression

In response to stimulants, such as serum, the yeast cells of the opportunistic fungal pathogen Candida albicans form germ tubes, which develop into hyphae. Yvh1p, one of the 29 protein phosphatases encoded in the C. albicans genome, has 45 % identity with the dual-specific phosphatase Yvh1p of the model yeast Saccharomyces cerevisiae. In this study, Yvh1p expression was not observed during the initial step of germ tube formation, although Yvh1p was expressed constitutively in cell cycle progression of yeast or hyphal cells. In an attempt to analyse the function of Yvh1p phosphatase, the complete ORFs of both alleles were deleted by replacement with hph200–URA3–hph200 and ARG4. Although YVH1 has nine single-nucleotide polymorphisms in its coding sequence, both YVH1 alleles were able to complement the YVH1 gene disruptant. The vegetative growth of Δyvh1 was significantly slower than the wild-type. The hyphal growth of Δyvh1 on agar, or in a liquid medium, was also slower than the wild-type because of the delay in nuclear division and septum formation, although germ tube formation was similar between the wild-type and the disruptant. Despite the slow hyphal growth, the expression of several hypha-specific genes in Δyvh1 was not delayed or repressed compared with that of the wild-type. Infection studies using mouse models revealed that the virulence of Δyvh1 was less than that of the wild-type. Thus, YVH1 contributes to normal vegetative yeast or hyphal cell cycle progression and pathogenicity, but not to germ tube formation.

Download Full-text

Differential expression of cytoplasmic proteins during yeast bud and germ tube formation in Candida albicans

Canadian Journal of Microbiology ◽

10.1139/m81-088 ◽

1981 ◽

Vol 27 (6) ◽

pp. 580-585 ◽

Cited By ~ 16

Author(s):

Louise A. Brown ◽

W. LaJean Chaffin

Keyword(s):

Gene Expression ◽

Candida Albicans ◽

Germ Tube ◽

Polyacrylamide Gel Electrophoresis ◽

Tube Formation ◽

Yeast Cells ◽

Cytoplasmic Proteins ◽

Specific Proteins ◽

Major Shift ◽

Dimorphic Yeast

Changes in the identity and quantity of proteins synthesized during morphogenesis may result from alterations in gene expression in the dimorphic yeast Candida albicans. Stationary phase yeast cells, upon resuming growth at 25 °C, form budding yeast and at 37 °C form germ tubes. In order to identify proteins associated with morphogenesis, we compared cytoplasmic proteins synthesized during germ tube and bud formation. Proteins synthesized during this period were labeled at four intervals with either [3H]leucine or [35S]methionine and separated by two-dimensional polyacrylamide gel electrophoresis. This study shows that, of the 230 proteins resolved on each gel, 5 were specific to the yeast morphology and 2 proteins showed reduction in net synthesis in the mycelial phase. There were, however, no mycelium-specific proteins at any labeling period. The majority of proteins were common to both morphologies and showed no major shift in number during resumption of growth. The observations reported here suggest that differential gene expression occurs during morphogenesis of C. albicans.

Download Full-text

Rates of germ tube formation from growing and non-growing yeast cells of Candida albicans

FEMS Microbiology Letters ◽

10.1016/0378-1097(91)90463-k ◽

1991 ◽

Vol 81 (1) ◽

pp. 15-18 ◽

Cited By ~ 1

Author(s):

A Buchan

Keyword(s):

Candida Albicans ◽

Germ Tube ◽

Tube Formation ◽

Yeast Cells

Download Full-text

Nutrient-limited yeast growth in Candida albicans: effect on yeast-mycelial transition

Canadian Journal of Microbiology ◽

10.1139/m80-015 ◽

1980 ◽

Vol 26 (1) ◽

pp. 102-105 ◽

Cited By ~ 12

Author(s):

William M. Bell ◽

W. LaJean Chaffin

Keyword(s):

Candida Albicans ◽

Stationary Phase ◽

Germ Tube ◽

Specific Effect ◽

Defined Medium ◽

Tube Formation ◽

Yeast Cells ◽

Yeast Growth ◽

Limiting Nutrient ◽

Final Cell Concentration

The yeast-mycelial transition in Candida albicans can be induced from yeast cells grown on minimal defined medium only in stationary phase. This study examined the inducibility of cultures in which growth was limited by the availability of the nutrients, glucose, NH4Cl, or galactose. The results showed that neither stationary phase nor cell cycle stage alone was a sufficient condition to support subsequent germ tube formation. In addition, final cell concentration alone was not a factor in inducibility. When a hundredfold decrease in growth was obtained by limiting any of the nutrients, a loss in inducibility was observed. However, the loss of inducibility differed with the limiting nutrient. Galactose, NH4Cl, and glucose-limited cultures showed respectively 15, 30, and 80% loss of inducibility. Thus the effect was associated with both carbon/energy and nitrogen-limited cells; however, glucose appeared to have a specific effect. These observations suggest that the metabolic state of the stationary phase yeast cell was an important factor in the subsequent ability to respond to conditions inducing germ tube formation.

Download Full-text

Germ tube induction in Candida albicans

Canadian Journal of Microbiology ◽

10.1139/m80-004 ◽

1980 ◽

Vol 26 (1) ◽

pp. 21-26 ◽

Cited By ~ 103

Author(s):

M. G. Shepherd ◽

Chiew Yoke Yin ◽

S. P. Ram ◽

P. A. Sullivan

Keyword(s):

Candida Albicans ◽

Germ Tube ◽

Potassium Cyanide ◽

Dry Weight ◽

Tube Formation ◽

Yeast Cells ◽

Leucine Incorporation ◽

Dna And Rna ◽

Rna Content ◽

Germ Tubes

A reproducible and simple system for the production of germ tubes from yeast cells of Candida albicans using glucose and glutamine as substrates has been described.During germ tube formation there was a doubling of the dry weight but the number of cells remained constant. Although the DNA content did not change for the first 4 h of germ tube formation, the RNA content more than doubled. The DNA and RNA content of C. albicans blastospores are 4.5 × 10−15 g per cell and 48 × 10−15 g per cell respectively.Nystatin, phenethyl alcohol, 2,4-dinitrophenol, azaserine, salicylhydroxamic acid, and 5-fluorocytosine were all effective inhibitors of germ tube formation. Cysteine, potassium cyanide, and polyoxin D did not prevent germination. The incorporation of both uracil and leucine occurred rapidly during germ tube formation. The inhibitors of RNA synthesis, actinomycin D, cordycepin, and daunomycin prevented germination and inhibited uracil incorporation. The translational inhibitors, trichodermin, aurin tricarboxylic acid, puromycin, and cyloheximide were effective in inhibiting both germ tube formation and leucine incorporation.

Download Full-text

Ras1-Induced Hyphal Development in Candida albicans Requires the Formin Bni1

Eukaryotic Cell ◽

10.1128/ec.4.10.1712-1724.2005 ◽

2005 ◽

Vol 4 (10) ◽

pp. 1712-1724 ◽

Cited By ~ 44

Author(s):

Ronny Martin ◽

Andrea Walther ◽

Jürgen Wendland

Keyword(s):

Candida Albicans ◽

Fluorescent Protein ◽

Hyphal Growth ◽

Time Lapse ◽

Tube Formation ◽

Effector Proteins ◽

Yeast Cells ◽

Hyphal Development ◽

Growth Defects

ABSTRACT Formins are downstream effector proteins of Rho-type GTPases and are involved in the organization of the actin cytoskeleton and actin cable assembly at sites of polarized cell growth. Here we show using in vivo time-lapse microscopy that deletion of the Candida albicans formin homolog BNI1 results in polarity defects during yeast growth and hyphal stages. Deletion of the second C. albicans formin, BNR1, resulted in elongated yeast cells with cell separation defects but did not interfere with the ability of bnr1 cells to initiate and maintain polarized hyphal growth. Yeast bni1 cells were swollen, showed an increased random budding pattern, and had a severe defect in cytokinesis, with enlarged bud necks. Induction of hyphal development in bni1 cells resulted in germ tube formation but was halted at the step of polarity maintenance. Bni1-green fluorescent protein is found persistently at the hyphal tip and colocalizes with a structure resembling the Spitzenkörper of true filamentous fungi. Introduction of constitutively active ras1 G13V in the bni1 strain or addition of cyclic AMP to the growth medium did not bypass bni1 hyphal growth defects. Similarly, these agents were not able to suppress hyphal growth defects in the wal1 mutant which is lacking the Wiskott-Aldrich syndrome protein (WASP) homolog. These results suggest that the maintenance of polarized hyphal growth in C. albicans requires coordinated regulation of two actin cytoskeletal pathways, including formin-mediated secretion and WASP-dependent endocytosis.

Download Full-text

CAP1, an Adenylate Cyclase-Associated Protein Gene, Regulates Bud-Hypha Transitions, Filamentous Growth, and Cyclic AMP Levels and Is Required for Virulence of Candida albicans

Journal of Bacteriology ◽

10.1128/jb.183.10.3211-3223.2001 ◽

2001 ◽

Vol 183 (10) ◽

pp. 3211-3223 ◽

Cited By ~ 118

Author(s):

Yong-Sun Bahn ◽

Paula Sundstrom

Keyword(s):

Candida Albicans ◽

Cyclic Amp ◽

Adenylate Cyclase ◽

Germ Tube ◽

Filamentous Growth ◽

Tube Formation ◽

Camp Signaling ◽

Solid Media ◽

Opportunistic Fungal Pathogen ◽

Camp Levels

ABSTRACT In response to a wide variety of environmental stimuli, the opportunistic fungal pathogen Candida albicans exits the budding cycle, producing germ tubes and hyphae concomitant with expression of virulence genes, such as that encoding hyphal wall protein 1 (HWP1). Biochemical studies implicate cyclic AMP (cAMP) increases in promoting bud-hypha transitions, but genetic evidence relating genes that control cAMP levels to bud-hypha transitions has not been reported. Adenylate cyclase-associated proteins (CAPs) of nonpathogenic fungi interact with Ras and adenylate cyclase to increase cAMP levels under specific environmental conditions. To initiate studies on the relationship between cAMP signaling and bud-hypha transitions in C. albicans, we identified, cloned, characterized, and disrupted the C. albicans CAP1 gene. C. albicans strains with inactivated CAP1 budded in conditions that led to germ tube formation in isogenic strains withCAP1. The addition of 10 mM cAMP and dibutyryl cAMP promoted bud-hypha transitions and filamentous growth in thecap1/cap1 mutant in liquid and solid media, respectively, showing clearly that cAMP promotes hypha formation in C. albicans. Increases in cytoplasmic cAMP preceding germ tube emergence in strains having CAP1 were markedly diminished in the budding cap1/cap1 mutant. C. albicans strains with deletions of both alleles ofCAP1 were avirulent in a mouse model of systemic candidiasis. The avirulence of a germ tube-deficientcap1/cap1 mutant coupled with the role of Cap1 in regulating cAMP levels shows that the Cap1-mediated cAMP signaling pathway is required for bud-hypha transitions, filamentous growth, and the pathogenesis of candidiasis.

Download Full-text