Morphogenesis In Candida Albicans Research Articles

Zinc levels of serum and cervicovaginal secretion in recurrent vulvovaginal candidiasis.

To determine whether zinc deficiency in serum or vulvovaginal secretion is a risk factor for recurrent vulvovaginal candidiasis. Prospective and controlled study. Department of Dermatology, University of Vienna. 21 women who had experienced at least three documented episodes of acute vulvovaginal candidiasis within the previous 12 months. Fifteen women without anamnesis of vulvovaginal candidiasis as a control group. Blood samples were drawn for measurement of plasma zinc levels. Lavage of the vagina and ectocervix was performed with sterile saline solution for measurement of cervicovaginal zinc levels. Zinc levels of serum and cervicovaginal secretions were determined by flame atomic absorption spectrophotometry. We found no significant difference in the mean zinc concentration of plasma and cervicovaginal secretions between the recurrent vulvovaginal candidiasis and the control group. (p value for serum = 0.71, p value for secretion = 0.80). Zinc levels of plasma and cervicovaginal secretions showed no correlation (patient group: r = -0.05, control group: r = -0.07). It is well known that zinc not only exerts a major impact on different immune functions, but also participates in growth and morphogenesis of Candida albicans. Our results could not confirm the previous hypothesis that zinc deficiency of serum is a risk factor in recurrent vulvovaginal candidiasis. It is possible that the local zinc level of cervicovaginal secretions essentially influences antifungal activity of third generation azole antimycotics.

Levels of plasma membrane H+-ATPase do not change during growth and morphogenesis of Candida albicans

A transient rise in the PM-ATPase activity was observed at the time of commitment of Candida albicans cells to either bud or hyphal formation. However, the changes in PM-ATPase activity did not correlate with the level of enzyme protein detected by ELISA. It was found to be fairly constant during differentiation, implying that there was no de novo synthesis of the protein. Post-translational modification(s) of enzyme protein is suggested to account for variation in PM-ATPase activity during morphogenesis.

Overexpression of the actin gene is associated with the morphogenesis of Candida albicans

A progressive increase in the synthesis of actin mRNA was observed by Northern blot analysis, when cells were induced to form germ tubes at 37°C by N-acetyl-D-glucosamine. Presence of trifluoperazine, a calmodulin inhibitor, or incubation of cells at 25°C, or by replacing N-acetyl-D-glucosamine with glucose which inhibited germ tube formation lowered this synthesis. Furthermore, in vitro translation of total RNA revealed an increase in the synthesis of actin (45 kDa) during germ tube formation. These results suggest for the first time that the expression of actin gene is regulated during morphogenesis of C. albicans.

Involvement of calcium, calmodulin and protein phosphorylation in morphogenesis of Candida albicans

N-Acetyl-D-glucosamine-induced germ tube formation in Candida albicans at 37 degrees C was accompanied by an increase in the rate of protein phosphorylation. The calmodulin antagonist trifluoperazine and the Ca2+ ionophore A23187, which inhibited germ tube formation, also reduced the rate of phosphorylation. The rate of phosphorylation was also reduced when cells were incubated at 25 degrees C, which favoured yeast-phase growth. Two-dimensional SDS-PAGE analysis of phosphoproteins from germ-tube-forming and yeast cells revealed two germ-tube-specific and three yeast-specific phosphoproteins. Germ tubes and hyphae had more calmodulin activity than yeast cells, irrespective of the germ-tube-inducing condition used. As a first step towards understanding the inhibitory effect of trifluoperazine on germ tube formation, calmodulin from C. albicans was purified to homogeneity. It was heat stable, and displayed a pronounced Ca2(+)-induced shift in electrophoretic mobility.

Receptor-mediated elevation of adenylate cyclase by luteinizing hormone in Candida albicans

Human luteinizing hormone (hLH) and the GTP analogue guanosine 5'-O-(3-thio)triphosphate stimulated morphogenesis in the dimorphic fungal pathogen Candida albicans. hLH bound specifically to subcellular fractions from C. albicans and stimulated adenylate cyclase activity in C. albicans microsomes. We provide the first demonstration of guanine-nucleotide-binding proteins (G-proteins) in C. albicans, and propose that the stimulation of C. albicans morphogenesis by hLH is mediated by a receptor-coupled adenylate cyclase system involving G-proteins.

A calmodulin inhibitor blocks morphogenesis in Candida albicans

A calmodulin inhibitor, trifluoperazine (TFP), can block yeast-to-germ-tube morphogenesis of Candida albicans induced by N-acetyl-d-glucosamine at 37°C. Furthermore, the ionophore A23187 can also block germ tube formation, which can be reversed by Ca2+. This indicates the possible involvement of calcium and calmodulin in morphogenesis of C. albicans. During germ tube formation, there is a progressive increase in the rate of protein phosphorylation, which is completely absent in non-germinating cells (yeast form). Trifluoperazine can also inhibit this phosphorylation indicating that protein phosphorylation may also be involved in this process.

A calmodulin inhibitor blocks morphogenesis in Candida albicans

A calmodulin inhibitor, trifluoperazine (TFP), can block yeast-to-germ-tube morphogenesis of Candida albicans induced by N-acetyl-d-glucosamine at 37°C. Furthermore, the ionophore A23187 can also block germ tube formation, which can be reversed by Ca2+. This indicates the possible involvement of calcium and calmodulin in morphogenesis of C. albicans. During germ tube formation, there is a progressive increase in the rate of protein phosphorylation, which is completely absent in non-germinating cells (yeast form). Trifluoperazine can also inhibit this phosphorylation indicating that protein phosphorylation may also be involved in this process.

The control of morphogenesis in Candida albicans.

Morphogenesis (germ-tube formation) in Candida albicans was induced gratuitously by N-acetylhexosamine derivatives (N-acetyl-glucosamine covalently linked to agarose, N-acetylmannosamine, hyaluronic acid, colloidal chitin, and mucin). These compounds were not taken up by the yeast cells and did not support growth. 2-Deoxyglucose was a potent inhibitor of germ-tube formation (50 microM), but did not affect the yeast growth yield at a concentration of 2.5 mM. 2-Deoxyglucose covalently linked to agarose did not affect germ-tube formation, and the inhibition by free 2-deoxyglucose was overcome by the addition of glucose to the germ-tube-forming cells. Glucose competitively inhibited 2-deoxyglucose uptake (Ki = 0.14 mM), and these data indicate that 2-deoxyglucose acted intracellularly.

Effect of cobalt and morphogenic autoregulatory substance (MARS) on morphogenesis of Candida albicans

Candida albicans yeast cells produce a factor, designated morphogenic autoregulatory substance (MARS), which suppresses yeast-to-mycelial conversion under conditions that support germination. In experiments designed to characterize MARS, the effect of various metals on MARS activity was tested. Cobalt but not zinc, iron, or other metals enhanced the ability of MARS to inhibit germination. Furthermore, uptake of cobalt by cells exposed to MARS was enhanced over cells in control medium if the cells were first incubated in a medium containing MARS for several hours prior to addition of cobalt to the medium. Uptake of zinc under similar conditions was not affected by MARS. The enhanced uptake of cobalt by MARS-exposed cells appears to be related to germination because such enhancement did not occur in strains of yeasts incapable of germination even in the absence of MARS.

Analysis of cytoplasmic antigens of the yeast and mycelial phases of Candida albicans by two-dimensional electrophoresis.

The extent of the macromolecular change accompanying yeast to mycelium morphogenesis of Candida albicans was analyzed by two-dimensional gel electrophoresis of the cytoplasmic proteins of the two growth forms after antibody cross-absorption experiments. Pure cultures of yeasts and true hyphae (i.e., without concomitant production of pseudohyphae) were grown in a synthetic low-sulfate medium (LSM). The two strains selected for this study were strain 4918, which produces pure mycelial (M) cultures in LSM at 37 degrees C (designated 4918-37M) and yeasts (Y) at 24 degrees C (4918-24Y), and strain 2252, which produces yeasts exclusively at both 24 and 37 degrees C in LSM (2252-24Y and 2252-37Y). The proteins of both strains were labeled at both temperatures with [35S]sulfate, and cytoplasmic fractions were prepared by mechanical disruption and ultracentrifugation. Rabbits were immunized with the 4918-24Y and 4918-37M cytoplasmic fractions to produce anti-yeast-phase and anti-mycelial-phase hyperimmune sera. Each radiolabeled cytoplasmic fraction was absorbed with anti-mycelial-phase immunoglobulin, anti-yeast immunoglobulin, and immunoglobulin from normal rabbit serum. Staphyloccal protein A was used to remove immune complexes. The labeled, nonabsorbed proteins were also analyzed by two-dimensional electrophoresis. Highly reproducible protein spot patterns were obtained which defined hundreds of proteins in each extract. The specificity of the immunoglobulin hundreds of proteins in each extract. The specificity of the immunoglobulin preparations was extremely broad, and as many as 168 cytoplasmic antigens were detected. Eighty-three antigens were recognized in the mycelial-phase extract only by the anti-mycelial-phase immunoglobulin. However, comparative analysis revealed that all of these proteins were present in at least one other extract. Therefore, none of them was unique to the mycelial morphology. Eleven antigens were detected in the 2252-37Y extract that were not present in the extracts from strain 4918, which indicates that proteins obtained from different strains may express similar antigenic determinants, but differ in their physiochemical properties.

Methionine biosynthesis and S-adenosylmethionine degradation during an induced morphogenesis of Candida albicans.

Seven strains of Candida albicans were used in studies designed to delineate altered biochemical activity during an induced yeast to filamentous morphogenesis. Four of the strains studied underwent a rapid (1–2 h) yeast to filamentous transformation in a defined medium with glycine as the main nitrogen source; three other strains of C. albicans remained yeast-like under the same growth conditions. Cell-free extracts, prepared from cells harvested after various time intervals of growth in glycine medium, were used to measure enzymic capacity to form methionine, via the enzyme S-adenosylmethionine (or methylmethionine) homocysteine methyltransferase, and degrade S-adenosylmethionine. Increased enzymic capacity to synthesize methionine (with S-adenosylmethionine as methyl donor) and degrade S-adenosylmethionine appeared to correlate best with a yeast to filamentous transformation of C. albicans. Intracellular S-adenosylmethionine content also decreased with time, in all seven strains, when the cells were cultured in the glycine medium. S-adenosylmethionine may play a key role in the biochemical alterations that occur during the morphogenesis of C. albicans.

Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick.

Balish, Edward (Syracuse University, Syracuse, N.Y.), and A. W. Phillips. Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick. J. Bacteriol. 91:1736-1743. 1966.-The effects of intestinal bacteria on the multiplication, morphogenesis, and infectivity of Candida albicans in the alimentary tract were investigated by comparing results obtained in germ-free and conventional chicks after oral inoculation. This challenge resulted in the establishment of large numbers of the pathogen in the alimentary tract of each group of chicks; these numbers were increased in crop contents from challenged bacteria-free chicks wherein hyphae predominated over the yeast form. These animals also had lesions of the crop epithelium containing numerous hyphae and few yeast-like forms. In contrast, challenged conventional chicks receiving an adequate diet displayed no evidence of infection. Their alimentary tract contained the yeast form of C. albicans; no hyphae were seen. Although we found bacterial inhibition of C. albicans multiplication in the alimentary tract, this in itself did not seem to explain the resistance to intestinal candidiasis in our conventional chicks. We argued that this resistance to infection was due chiefly to the prevention of hyphal development in C. albicans by intestinal bacteria. C. albicans in the gut of our conventional chicks resulted in some increase in numbers of enterococci in contents from the crop. Increased pH values in contents from the gut of germ-free chicks were not clearly related to infection after challenge. The E(h) of the above crop contents were only slightly decreased in the germ-free crop. Thus the E(h) did not appear to be involved in susceptibility to infection. Invasion of the blood stream and kidneys of conventional chicks by the yeast form of C. albicans occurred in challenged animals receiving a purified diet which had been radiation-sterilized and stored for 6 months at room temperature (25 C). Their growth rate decreased and they became moribund; no hyphae were observed in tissues or intestine of these animals. Challenged bacteria-free chicks receiving the same diet were resistant to the above invasion, although they had crop lesions containing hyphae as described. The resistance of these chicks to systemic invasion was attributed to absence of intestinal bacteria competing for low levels of vitamins in the stored diet. Germ-free chicks had decreased levels of serum gamma-globulin which increased after challenge, whereas this value was unchanged in conventional birds after challenge.

Chlamydospore production in candida albicans

A review of the literature correlated with laboratory studies of the influence of carbon source, temperature, and pH on chlamydospore formation, substantiate the enzymatic hypothesis of morphogenesis inCandida albicans.