Production and characterisation of a monoclonal antibody to a cell-surface, glucomannoprotein constituent of Candida albicans and other pathogenic Candida species

A murine monoclonal antibody (MAB AF-1) class IgM was raised to a soluble glucomannoprotein extract (GMP) of Candida albicans. Agglutination and indirect immunofluorescence assays with purified MAB showed that AF-1 was directed against a cell-surface epitope shared by C. albicans serotypes A and B, C. tropicalis, C. guilliermondii and C. viswanathii, but not by C. krusei, C. parapsilosis, C. kefyr (pseudotropicalis) and T. glabrata. Treatment with heat, protease or periodate-treated GMP and with other cell-wall extracts of C. albicans provided evidence that the epitope recognised by MAB AF-1 is carried by the polysaccharide moiety of cell-surface glucomannoprotein molecule(s).

Enzyme activities in oleaginous yeasts accumulating and utilizing exogenous or endogenous lipids

The activities of ATP: citrate lyase (ACL; EC 4. 1. 3. 8), carnitine acetyltransferase (CAT; EC 2. 3. 1. 7), NADP+-dependent isocitrate dehydrogenase (ICDH; EC 1. 1. 1. 42), isocitrate lyase (ICL; EC 4. 1. 3. 1) and malic enzyme (malate dehydrogenase; EC 1. 1. 1. 40) were measured in four oleaginous yeasts, Candida curvata D, Trichosporon cutaneum and two strains of Rhodosporidium toruloides, grown either to accumulate lipid, or to utilize their own lipid reserves or an exogenous supply of lipid. During lipid utilization, activities of ACL and malic enzyme diminished to low levels; CAT and ICL increased considerably in activity and ICDH activity was slightly increased but catalase (EC 1. 11. 1. 6) diminished in activity in both strains of R. toruloides. In all cases, yeasts utilizing exogenous lipid showed greater changes in enzyme activities than cells utilizing their endogenous reserves. Electron micrographs of Candida curvata D showed proliferation of peroxisomes in starved cells utilizing their own lipid reserve though peroxisomes were more in evidence when the yeast had been grown on exogenous lipid. In Lipomyces starkeyi, which shows only minimal utilization of its stored lipid and furthermore cannot grow on exogenous lipid, only the occasional peroxisome was seen when cells were starved of carbon.

Oral hairy leukoplakia: ultrastructural observations

On the basis of the clinical appearance and the light microscopic findings, we determined 16 biopsy specimens to be possible examples of oral hairy leukoplakia. All 16 specimens were studied by means of electron microscopy. Ten of these specimens contained typical herpes-type viral particles in the epithelial cells of the upper stratum spinosum. None of the specimens contained ultrastructural evidence of human papillomaviruses.

Occurrence and possible roles of acetoacetyl-CoA thiolase and 3-ketoacyl-CoA thiolase in peroxisomes of an n-alkane-grown yeast, Candida tropicalis

Two kinds of 3-ketoacyl-CoA thiolases were found in the peroxisomes of Candida tropicalis cells grown on n-alkanes (C10-C13). One was a typical acetoacetyl-CoA thiolase specific only to acetoacetyl-CoA, while another was 3-ketoacyl-CoA thiolase showing high activities on the longer chain substrates. A high level of the latter thiolase activity in alkane-grown cells was similar to that of other enzymes constituting the fatty acid beta-oxidation system in yeast peroxisomes. These facts suggest that the complete degradation of fatty acids to acetyl-CoA is carried out in yeast peroxisomes by the cooperative contribution of acetoacetyl-CoA thiolase and 3-ketoacyl-CoA thiolase.

Differential location of regulatory and nonregulatory trehalases in Candida utilis cells

The isolation of vacuoles by density gradient centrifugation of protoplast lysates from Candida utilis cells showed a high specific activity for nonregulatory trehalase in vacuoles whereas the regulatory trehalase activatable by phosphorylation behaves as a cytoplasmic enzyme. The vacuolar trehalase is a glycoprotein that can be precipitated by Con A-Sepharose. Treatment of this enzyme with endo H reduced its reactivity with the lectin without loss of enzyme activity and decreased its apparent molecular weight by gel filtration.

Morphological basis for multiple interactions of ethidium bromide (EB) with yeast Candida utilis

Exposure of yeast cells to EB produced multiple effects on the cellular organelles: changes in the plasma membrane characterized by 75 to 110 nm deep pits; polymorphisms of the mitochondria ranging from cup-shaped, ring-shaped, ribbon-shaped, dumbbell-shaped structures to finally the formation of very elongated mitochondria (up to 4.5 micron in length); an increase in the length and number of endoplasmic reticulum; an increase in the number of cytoplasmic vesicles whose diameter varied between 25 to 45 nm. Furthermore, EB inhibited cytochrome c oxidase and cytochrome b biosynthesis, stimulated cytochrome c biosynthesis and uncoupled oxidative phosphorylation.

A 31P NMR study of the internal pH of yeast peroxisomes

The internal pH of peroxisomes in the yeasts Hansenula polymorpha, Candida utilis and Trichosporon cutaneum X4 was estimated by 31P nuclear magnetic resonance (NMR) spectroscopy. 31P NMR spectra of suspensions of intact cells of these yeasts, grown under conditions of extensive peroxisomal proliferation, displayed two prominent Pi-peaks at different chemical shift positions. In control cells grown on glucose, which contain very few peroxisomes, only a single peak was observed. This latter peak, which was detected under all growth conditions, was assigned to cytosolic Pi at pH 7.1. The additional peak present in spectra of peroxisome-containing cells, reflected Pi at a considerably lower pH of approximately 5.8-6.0. Pi at a considerably lower pH of approximately 5.8-6.0. Experiments with the protonophore carbonyl cyanide m-chlorophenylhydrazon (CCCP) and the ionophores valinomycin and nigericin revealed that separation of the two Pi-peaks was caused by a pH-gradient across a membrane separating the two pools. Experiments with chloroquine confirmed the acidic nature of one of these pools. In a number of transfer experiments with the yeast H. polymorpha it was shown that the relative intensity of the Pi-signal at the low pH-position was correlated to the peroxisomal volume fraction. These results strongly suggest that this peak has to be assigned to Pi in peroxisomes, which therefore are acidic in nature. The presence of peroxisome-associated Pi was confirmed cytochemically.

A proton-translocating adenosine triphosphatase is associated with the peroxisomal membrane of yeasts

The association of an ATPase with the yeast peroxisomal membrane was established by both biochemical and cytochemical procedures. Peroxisomes were purified from protoplast homogenates of the methanol-grown yeast Hansenula polymorpha by differential and sucrose gradient centrifugation. Biochemical analysis revealed that ATPase activity was associated with the peroxisomal peak fractions which were identified on the basis of alcohol oxidase and catalase activity. The properties of this ATPase closely resembled those of the mitochondrial ATPase of this yeast. The enzyme was Mg2+-dependent, had a pH optimum of approximately 8.5 and was sensitive to N,N'-dicyclohexylcarbodiimide (DCCD), oligomycin and azide, but not to vanadate. A major difference was the apparent Km for ATP which was 4-6 mM for the peroxisomal ATPase compared to 0.6-0.9 mM for the mitochondrial enzyme. Cytochemical experiments indicated that the peroxisomal ATPase was associated with the membranes surrounding these organelles. After incubations with CeCl3 and ATP specific reaction products were localized on the peroxisomal membrane, both when unfixed isolated peroxisomes or formaldehyde-fixed protoplasts were used. This staining was strictly ATP-dependent; in controls performed in the absence of substrate, in the presence of glycerol 2-phosphate instead of ATP, or in the presence of DCCD, staining was invariably absent. Similar staining patterns were observed in subcellular fractions and protoplasts of Candida utilis and Trichosporon cutaneum X4, grown in the presence of ethanol/ethylamine or ethylamine, respectively.

Mitochondrial DNA in Candida pintolopesii, a yeast indigenous to the surface of the secreting epithelium of the murine stomach

Candida pintolopesii 108-1 is an indigenous yeast which colonizes the surface of the secreting gastric mucosa of mice. We have been exploring the aerobic respiratory capacities of this organism in reference to its capacity to colonize the stomach surface, an environment that could contain little oxygen for microbial growth. In this paper, we report mitochondrial DNA and membranes in cells of a strain of this yeast isolated from the gastric epithelium of a mouse and compare the findings with those made by other investigators in studies of Saccharomyces cerevisiae. Putative mitochondrial DNA was isolated from crude lysates of C. pintolopesii and S. cerevisiae as fluorescing bands in CsCl gradients containing 4',6-diamidino-2-phenylindole. The DNA from C. pintolopesii hybridized with a 32P-labeled DNA probe for the 21S rRNA gene encoded by mitochondrial DNA in S. cerevisiae. Postvital cell staining with 4',6-diamidino-2-phenylindole and rhodamine 123 revealed mitochondrial DNA and membranes, respectively, in the cytoplasm of intact C. pintolopesii cells. The staining patterns were generally similar to those reported for S. cerevisiae. Finally, structures similar to those reported to be mitochondria in electron micrographs of S. cerevisiae were seen in preparations of C. pintolopesii cells examined by transmission electron microscopy. These data confirm findings from studies of its respiratory capacity published earlier that a strain of C. pintolopesii isolated directly from its native habitat has functional mitochondria.

Yeasts in juvenile periodontitis. Preliminary observations by scanning electron microscopy

Through the use of the electron microscope, yeasts were found invading gingival connective tissue in juvenile periodontitis (JP). Samples (3-mm punch biopsies, including epithelium and underlying connective tissue) were taken apically to periodontal pockets before and after patient treatment with spiramycin. Some samples underwent in vitro treatment with spiramycin. Oval and round yeast cells were found before and after in vivo and after in vitro spiramycin treatment. Larger numbers of yeast cells were seen after spiramycin treatment indicating that their growth might be favored after patient treatment with this antibiotic. This observation has an obvious clinical implication. Budding processes, indicating active yeast multiplication, were observed. Some yeast cells also showed the presence of glycocalyx. Further studies on the role of yeast in the pathogenesis of JP are necessary.

Induction, identification, and cell-free translation of mRNAs coding for peroxisomal proteins in Candida tropicalis

Peroxisomes have been purified from Candida tropicalis grown on oleic acid and shown to be nearly pure by marker enzyme analysis, electron microscopy, and comparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They contain approximately 20 polypeptides, among which acyl-CoA oxidase, trifunctional hydratase-dehydrogenase-epimerase, and catalase have been identified. Rabbit antisera have been elicited that react with these three proteins. When C. tropicalis is grown on alkanes, a dozen mRNAs are strikingly induced. Nine of the 12 induced mRNAs code for polypeptides that comigrate in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with peroxisomal proteins, among which three have been identified immunochemically as the acyl-CoA oxidase, the trifunctional protein, and catalase. These results indicate that some genes coding for peroxisomal proteins are strongly expressed during growth of C. tropicalis on alkanes. The data are consistent with evidence in other species that peroxisomes form by the post-translational incorporation of newly made proteins into pre-existing peroxisomes, generally without proteolytic processing, followed by peroxisome division.

A 96-well epifluorescence assay for rapid assessment of compounds inhibitory to Candida spp

A rapid method for the screening of potential antifungal compounds was developed. A variety of compounds were tested against regenerating protoplasts of Candida spp. in a microtiter format. The degree of cell wall formation was assessed by staining with Cellufluor (Polysciences, Inc., Warrington, Pa.), a fluorochrome with known affinity for chitin, followed by determination of fluorescence by using a Dynatech Microfluor reader (Dynatech Laboratories, Inc., Alexandria, Va.). Compounds with known activity against the cell wall or cytoplasmic membrane of fungi inhibited wall synthesis in a concentration-dependent fashion. Treatment with 5-fluorocytosine, however, resulted in no inhibition. In general, protoplasts of C. albicans regenerated more quickly and were more sensitive to the compounds tested than protoplasts of C. tropicalis and C. parapsilosis. While the described method is not specific for a given class of antifungal agents, it may prove useful for testing large numbers of compounds quickly.

Effects of antineoplastic agents on growth, morphology and metabolism of Torulopsis glabrata

The effect of treatment by a number of antineoplastic agents on the growth, ultrastructure and macromolecular synthesis of T. glabrata was studied. Many differences were noted in the response of this yeast to these agents. Thiotepa and methotrexate inhibited the growth of T. glabrata, while it was resistant to endoxan-asta and vincristine sulphate. A variation of morphological response of T. glabrata was also observed. Methotrexate enhanced filamentation while thiotepa influenced the surface structures of the cells, resulting in loss of cytoplasmic materials and cell collapse. The other two drugs had little or no effect on the morphology of the yeast tested. The incorporation of precursors for macromolecular synthesis of T. glabrata in the presence of thiotepa and methotrexate was restricted. Thiotepa affected the uptake of precursors of RNA, DNA and protein limiting them to between 62 and 66% of the control values. In contrast, methotrexate limited the uptake of macromolecular precursors to a lesser extent. The possible mechanism of action of antineoplastic agents against yeast and the clinical implications of these findings are discussed.

Yeasts in molecular biology. Spheroplast preparation with Candida utilis, Schizosaccharomyces pombe and Saccharomyces cerevisiae

Efficient preparation of spheroplasts from Candida utilis, Saccharomyces cerevisiae, and Schizosaccharomyces pombe, using a purified mixture of enzymes from Trichoderma harzianum, is described. Limitations of other methods, and differences between yeasts are demonstrated.

Anticandidal activities of terconazole, a broad-spectrum antimycotic

Terconazole is a new triazole ketal derivative with broad-spectrum in vitro and in vivo antifungal activities. This study further characterizes the effects of terconazole in vitro on yeast cell growth, viability, and morphology. Terconazole inhibited the growth of Candida albicans ATCC 44859 in a concentration-related manner, but with modest effects noted at levels from 10(-8) to 10(-5) M when the yeast was grown on media favoring the cell form. The inhibitory potency of terconazole on yeast cell viability varied with the strain and species of Candida tested. The susceptibility of C. albicans ATCC 44859 to terconazole was markedly enhanced when the yeast was grown on Eagle minimum essential medium, which favors mycelium formation. The effects of terconazole on the morphology of yeast cells (grown on Eagle minimum essential medium) were shown by phase-contrast and electron microscopy. There is a progression of changes, from loss of mycelia formation at 10(-8) M terconazole through complete necrosis at 10(-4) M.

[Role of cell wall components in yeasts of the genus Candida in the morphology of the cell]

The object of this work was to study the function of the mannan and glucan layers in the cell wall of Candida yeasts. When the outer mannan layer was removed with proteinases, the cells became round and their volume increased by a factor of 2.2. The contribution of the above layers into the elastic properties of the cell wall was estimated in qualitative terms. Apparently, mannans play a more important role in cell morphogenesis than it was supposed earlier.

The membrane proteins of the methanol-induced peroxisome of Candida boidinii. Initial characterization and generation of monoclonal antibodies

Peroxisomes are massively induced when methylotrophic yeasts are cultured on methanol as the sole carbon and energy source. An analysis of the protein composition of the peroxisomal membrane and the generation of probes against two peroxisomal membrane proteins (PMPs) have been undertaken. Peroxisomes from Candida boidinii were obtained from sucrose gradients as previously described or from a novel one-step purification of the organelle on a Percoll gradient. The protein composition of the membranes from these two preparations was virtually identical. About 10 proteins comprise nearly all of its protein mass. The most prominent proteins have molecular masses of 120, 100, 47, 31-32 (a triplet), and 20 kDa; significant amounts of alcohol oxidase and dihydroxyacetone synthase, the two abundant matrix proteins, also remain associated with the membrane. Glycosylation of the membrane proteins could not be detected. Exposure of the membrane to chaotropes shows that PMPs 100 and 20 are the most easily removable, whereas PMP 47 appears to be the most tightly associated. Mice were injected with peroxisomal membrane, and hybridoma lines were isolated that produced antibody against PMP 20, PMP 47, and dihydroxyacetone synthase. Indirect immunofluorescence with these monoclonal antibodies confirmed that all three proteins are localized to the peroxisomal cluster. Immunoblotting experiments demonstrated that peroxisomal membrane as well as matrix proteins are induced by methanol.

Purification of peroxisomal malate synthase from alkane-grown Candida tropicalis and some properties of the purified enzyme

Malate synthase, one of the key enzymes in the glyoxylate cycle, was purified from peroxisomes of alkane-grown yeast, Candida tropicalis. The enzyme was mainly localized in the matrix of peroxisomes, judging from subcellular fractionation followed by exposure of the organelles to hypotonic conditions. The molecular mass of this peroxisomal malate synthase was determined to be 250,000 daltons by gel filtration on a Sepharose 6B column as well as by ultracentrifugation. On sodium dodecylsulfate/polyacrylamide slab-gel electrophoresis, the molecular mass of the subunit of the enzyme was demonstrated to be 61,000 daltons. These results revealed that the native form of this enzyme was homo-tetrameric. Peroxisomal malate synthase showed the optimal activity pH at 8.0 and absolutely required Mg2+ for enzymatic activity. The Km values for Mg2+, acetyl-CoA and glyoxylate were 4.7 mM, 80 microM and 1.0 mM, respectively.

Zygoascus hellenicus gen. nov., sp. nov., the teleomorph of Candida hellenica (= C. inositophila = C. steatolytica)

The anamorphic yeast species Candida hellenica, C. inositophila and C. steatolytica were found to constitute haploid mating types of an undescribed, filamentous heterothallic Endomycete. The new genus Zygoascus is proposed for the teleomorph. Descriptions are given of the genus and type species, Z. hellenicus.

Degradative inactivation of the peroxisomal enzyme, alcohol oxidase, during adaptation of methanol-grown Candida boidinii to ethanol

Adaptation of methanol-grown C. boidinii to ethanol-utilization in non-growing cells resulted in decreased activity of the peroxisomal enzyme alcohol oxidase. Re-appearance of alcohol oxidase activity was dependent on protein synthesis de novo. Degradation of alcohol oxidase protein was shown to parallel the decrease in activity. Adaptation of methanol-grown cells to ethanol-utilization resulted in increased absorbance due to cytochromes and decreased absorbance due to flavoprotein. Decrease in alcohol oxidase activity was associated with loss of the flavin coenzyme, FAD, from the organisms and the appearance of flavins (FAD, FMN, riboflavin) in the surrounding medium. Electron microscopic observations showed that general degradation of whole peroxisomes rather than specific loss of crystalline cores (alcohol oxidase protein) occurred during the adaptation.

[Importance of cellular homogenization for the posterior isolation of plasma membranes of the Candida utilis yeast]

Candida utilis plasma membranes were isolated from different homogenized, either whole cells or spheroplasts, by centrifugation and aggregation of mitochondrial and internal membranes at pH 4.0. As judged by electron microscopy, chemical analysis, disc electrophoresis and enzymatic assays, membrane preparations with different degrees of purity were obtained. The purest plasma membranes were those prepared by homogenization of spheroplasts in the Omnimixer Sorvall followed aggregation at mitochondrial isoelectric point as described above.

Dihydroxyacetone synthase is an abundant constituent of the methanol-induced peroxisome of Candida boidinii

Methylotrophic yeasts induce large peroxisomes when grown on methanol. The recent ability to stabilize and isolate these peroxisomes at pH 5.5 has led to the demonstration that two polypeptides comprise the bulk of the peroxisome of Candida boidinii, alcohol oxidase, and a 79-kDa species, determined by sodium dodecyl sulfate-polyacrylamide electrophoresis (Goodman, J.M., Scott, C.W., Donahue, P.N., and Atherton, J.P. (1984) J. Biol. Chem. 259, 8485-8493). The 79-kDa peroxisomal protein is now identified as dihydroxyacetone synthase, the first enzyme in the assimilatory pathway of formaldehyde utilization. This identification is based on several criteria: The enzyme activity is mainly in a particulate fraction at pH 5.5 but not at pH 8.0. It copurifies with alcohol oxidase and catalase on sucrose gradients. The 79-kDa protein behaves as a 135,000-kDa dimer on gel filtration, similar to the published behavior of the enzyme. The specific activity of dihydroxyacetone synthase in the pure 79-kDa preparation (3.20 units/mg of protein) is close to that reported for the purified enzyme (3.88 units/mg of protein). Antibodies against dihydroxyacetone synthase were used to show that its synthesis, induction, and assembly are similar to that of alcohol oxidase. Neither contains a detectable cleaved leader sequence and both are assembled post-translationally. The localization of dihydroxyacetone synthase to the peroxisome may influence the regulation of the two pathways of formaldehyde utilization and may protect the cell from damage by formaldehyde.

Relationship between growth inhibition and mitochondrial function in petite-negative yeasts. I. Effects of antibiotics and dyes upon pathogenic and non-pathogenic Candida species

Antibiotics and dyes which preclude growth of Saccharomyces cerevisiae in media containing oxidizable carbon sources arrested the growth of Candida albicans, Candida tropicalis and Candida utilis even in glucose medium. The growth in the presence of sub-inhibitory concentrations of the various antibiotics and dyes determined a reduction in the cell survival but with no accumulation of respiratory deficient mutants. Under these culture conditions, the total respiration declined leaving a residual antimycin A-resistant--hydroxamate-sensitive O2 uptake, and the amount of the respiratory cytochromes aa3 and b synthesized was reduced. SDS gel electrophoresis of soluble proteins prepared from the antibiotic-treated cells showed some bands in the MW range 92-100 K, which became faint after the cells were grown in the presence of some mitochondrial inhibitors. The ultrastructural analysis of these cells evidenced disappearance of the mitochondrial cristae and their replacement by unfolded membranes. The data obtained suggest that the petite negative trait of Candida could depend on the non-viability or on the very low viability of those cells which have lost their mitochondrial function.