Degradation of microbodies in relation to activities of alcohol oxidase and catalase in Candida boidinii

Degradation of microbodies in the methanol-utilizing yeast Candida boidinii was mainly studied by electron microscopical observation. The yeast cells precultured on methanol medium contained five to six microbodies per section and showed high activities of alcohol oxidase, catalase, formaldehyde dehydrogenase and formate dehydrogenase. When the precultured cells were transferred into an ethanol medium the number of microbodies and concomitantly the activities of alcohol oxidase and catalase decreased. After 6 h of cultivation microbodies were hardly detected. Also the activity of alcohol oxidase was not measurable and catalase activity was reduced to one tenth, whereas the activities of formaldehyde dehydrogenase and formate dehydrogenase decreased only to about 70%. Experiments with methanol-grown cells transferred into an ethanol medium without nitrogen source indicated that the inactivation of alcohol oxidase and catalase does not require protein synthesis. However, the reappearance of these enzymes is presumably due to de novo protein synthesis as shown by experiments with cycloheximide.

[Cryofractographic study of the structure of yeast cells found in an anabiotic state]

Cryofractographic studies of normally growing yeast cells have shown that the length, number and arrangement of slit-like invaginations, as well as the number, frequency of arrangement and dimensions of pores on the nucleolemma, differ among various yeast species. The data on the structure of various organoids published earlier have been confirmed. The volume of all cellular organoids, with an exception of mitochondria, decreases upon dehydration. The invaginations of the plasmalemma coalesce to form a common network. This is important in the course of changes in the volume and density of the cytoplasm of cells in the anabiotic state, maintaining the structural connection of the plasmalemma with the cellular contents, which is necessary for the survival of an organism under extreme conditions.

Chemical and structural alterations at the cell surface of Candida tropicalis, induced by hydrocarbon substrate

The surface-localized polysaccharide of alkane-grown cells of Candida tropicalis was identified as mannan containing approximately 4% covalently linked fatty acids. Glucose-grown cells lacked the mannan-fatty acid complex. The surface structure of alkane-grown cells showed a radial arrangement of the wall polymers, with protruding parts. The cell surface of glucose-grown cells was smooth, with a coherent outer limit. The mannan was localized by using concanavalin A. Masking of the mannan with concanavalin A reduced the binding affinity of the surface for alkane, indicating the involvement of the surface-localized mannan-fatty acid complex in the binding of alkanes.

Virus-like particles in yeast: isolation and infectivity

Virus-like particles containing electron dense cores are seen in thin sections of intact and degenerated cells of a thermosensitive (ts) strain of Candida tropicalis. A particulate fraction not present in wild-type cells has been isolated from the ts cells disrupted by pressure. The particles are 80-120 nm in diameter. Empty particles with a central cavity are observed. The method of infecting mating pairs of Saccharomyces cerevisiae by partially purified particles is described.

Recombination after protoplast fusion in the yeast Candida tropicalis

Candida tropicalis protoplasts obtained by snail enzyme treatment were induced to fuse by the use of polyethylene-glycol. Heterokaryons formed by two auxotrophic strains were selected by complementation on minimal medium. These heterokaryons were unstable and readily dissociated into their nuclear components. Under appropriate conditions, the parental nuclei of an heterokaryon fused. The homokaryon so obtained was unstable and segregated into various types of auxotrophic and prototrophic recombinants.

[Isolation and characteristics of the lipid granules of Candida tropicalis yeasts]

Preparative isolation of lipid granules from the protoplasts of Candida tropicalis was conducted by a technique of flotation in a stepwise density gradient. Parameters were selected for decomposing the protoplasts under hypotonic and isotonic conditions which made it possible to preserve the lipid granules being isolated intact, as well as parameters of a density gradient and centrifugation. The specific content of lipids, proteins and low molecular weight compounds was assayed using labeled compounds in the lipid granules which were isolated from yeast cells cultivated on various carbon substrates (1-6(-14C)-glucose and 1(-14C-octadecane). The lipid composition of the spherosomes was determined. If the yeast was grown on glucose, lipids localized in the lipid granules were represented mainly by triglycerides whose carbon constituted 69 per cent of the total lipid carbon. If it was cultivated on n-octadecane, these lipids were represented by hydrocarbons (51 per cent) and triglycerides (22 per cent). The structures isolated possessed a small lipase activity. The specific lipase activity of the lipid granules was lower by 16 per cent than that of the cell protoplast.

Location of mannan and chitin on thin sections of budding yeasts with gold markers

Mannan was located on thin sections of Saccharomyces cerevisiae and Candida utilis with the homologous anti-mannan antibodies or with Concanavalin A, both labelled with gold granules. Fully synthesized mannan was found in the cell walls, on the plasmalemma and within the cytoplasm sometimes associated with vesicles and vacuoles. Chitin or its oligomers were located with wheat germ agglutinin in the bud scars but also in the cell wall and the cytoplasm near the plasmalemma. Both mannan and chitin or its oligomers were found in the forming septum and are synthesized within the cytoplasm. The gold method was also suitable for marking mannan and chitin simultaneously.

[New scanning electron microscopy contribution to the study of yeast protoplasts]

Study by scanning electron microscopy enables us to describe with precision the morphology of protoplasts. We can confirm that the wrinkles more or less perceptible on the protoplasts studied, do belong to the morphology of those just mentioned, that the presence or the absence of globulous component is connected with the physiological activity of the cell and that it is possible to distinguish the different protoplasts thanks to their morphological aspect.

Influence of specific growth limitation and dilution rate on the phosphorylation efficiency and cytochrome content of mitochondria of Candida utilis NCYC 321

With Candida utilis cells that had been removed directly from a 61 chemostat culture, in steady state, well-coupled mitochondria generally could be isolated. This requires a modified snail-gut enzyme procedure that allowed the total processing time to be decreased to 3 h, or less. Examination of these mitochondria in an oxygraph showed the presence of 3 sites of energy conservation when the cells were grown at various dilution rates between 0.1 and 0.45 h-1 in environments that were, successively, glucose-, ammonia-, magnesium-, phosphate- and sulphate-limited. Potassium-limited cells also apparently possessed 3 sites of oxidative phosphorylation when growing at dilution rates greater than 0.2 h-1, but only 2 sites when growing at lower dilution rates. Analysis of cytochrome spectra obtained with these intact mitochondria revealed large quantitative (but not qualitative) differences, depending on the environmental conditions under which the yeast had been cultured. In particular, comparison of the ratio of cytochrome b to cytochrome a showed a pattern of change with dilution rate in mitochondria from potassium-limited cells that was distinctly different from those evident in mitochondria from cells that had been limited in their growth by the availability of other nutrients.

[Several properties of the extracellular vesicles of Candida tropicalis yeasts grown on n-alkanes]

Vesicles with a high content of phospholipids were found when Candida tropicalis IBFM-303 was cultivated on n-alkanes. The vesicles were extracellular, and their inner content had a fine-grained structure confined within a monolayer membrane. The number of the vesicles increased in the course of growth and depended on the concentration of n-alkanes in the medium. When the vesicles were added to an inoculate of C. tropicalis IBFM-303, the growth of cells decelerated and the biomass yield decreased. The paper presents experimental results concerning the chemical composition and the activity of some enzymes of these extracellular structures.

Cell surface topography of Candida and Leucosporidium yeasts as revealed by scanning electron microscopy

The cell surface topography of the following yeast strains was examined by scanning electron microscopy: Candida slooffii, C. lipolytica, Leucosporidium frigidum, and L. nivalis. Multipolar and lateral budding were observed in the Candida yeasts in contrast to bipolar budding in the Leucosporidium species. The cell surface topography and the morphology of the bud and birth scars in these yeasts differed markedly. Apart from the bud and birth scars, the cells of C. slooffii showed a relatively smooth topography. The bud scars were seen as a circular ridge of wall material surrounding a markedly convex scar plug. Birth scars were raised, rounded structures, which appeared to distend upon cell growth. In contrast, bud scars of C. lipolytica were platelike, lacked a distinct annulus of wall material, and were much less protuberent than those of C. slooffii. Birth scars were a more permanent feature of these cells. The topography of Leucosporidium yeasts was characterized by the presence of numerous protrusions on the cell surface. In some cases, the entire cell surface was covered by these protrusions. There appeared to be some correlations between the age of the cell and the extent of surface protrusions and degree of surface convolution...

Microbody of n-alkane-grown yeast. Enzyme localization in the isolated microbody

Microbodies appearing abundantly in n-alkane-grown cells of Candida tropicalis pK 233 were isolated by means of sucrose density gradient centrifugation. Electron microscopical observation showed that the microbodies isolated were intact. Localization of catalase and D-amino acid oxidase in the isolated microbodies was confirmed. Isocitrate lyase, melate synthase and NADP-linked isocitrate dehydrogenase were also located in the microbody, but malate dehydrogenase, citrate synthase, aconitase and NAD-linked isocitrate dehydrogenase were not. Neither cytochrome P-450 not NADPH-cytochrome c reductase, the components involved in the n-alkane hydroxylation system of the yeast, were detected in the microbody fraction.

Structure of mitochondria and vacuoles of Candida utilis and Schizosaccharomyces pombe studied by electron microscopy of serial thin sections and model building

The structure of mitochondria and of vacuoles in Candida utilis and Schizosaccharomyces pombe has been studied by electron microscopy of serial thin sections and subsequent model building. The models of the two cells of C. utilis which were studied confirmed our earlier findings, made by high voltage electron microscopy of thick sections, that there is a single, branched and continuous mitochondrial network in the cell (Davison & Garland, 1975). A model of a S. pombe cell showed that the mitochondrial structure was far more continuous than expected from inspection of thin sections, there being but two large and two small mitochondria. The models demonstrated that the few large vacuoles in C. utilis were interconnected into a single cluster, whereas in S. pombe there were two separate complexes of interconnected vacuoles towards each pole of the cell.

[Experimental investigations on ultraweak photonemission form biological systems (author's transl)]

Measurements on untreated yeast cells, potato- and cucumber seedlings have confirmed the existence of photon emission from biological systems known as "ultraweak luminescence". The intensity is of the order of 10(2) counts per second, and the spectral distrubtion shows a maximum near 550 nm. The dependence of th photon emission on certain chemicals has been investigated. Some chemicals, as for instance acetone, intensify the photon emission from cucumber seedlings without essential change of the spectral distribution. On the other hand, NaCl leads to a shift to the red region of the spectrum. The treatment of EAT-cells by 4-Hydroperoxycyclofosfamide involves a nonlinear enhancement of the intensity with increasing concentration. There are some indications that collective interactions of the system are more appropriate than simple chemiluminescence reactions.

[Cytological mechanisms involved in assimilation of n-alkanes by yeasts]

The paper describes cytological mechanism of adaptation of yeasts to assimilation of aliphatic hydrocarbons added to a growth medium as a sole source of carbon. The process was studied by light optical and electron microscopy, employing fluorescent labelling and electron microscopy contrasting. Two types of yeasts were found, which differed by the response of the cell walls to hydrocarbons: those that formed "channels" and those that did not form them. Cytological response to hydrocarbon assimilation was detected also in the mitochondria and canals of the endoplasmic reticulum. Components of the Golgi apparatus may also participate in this process, in particular, in formation of peroxisomes (microbodies). Close contacts of the yeast cells with the hydrocarbon being assimilated is important; assimilation may start in a close vicinity of the cell walls. The rate of flavin production by Candida tropicalis 303 IBFM increases during growth on solid paraffins, beginning with C20-paraffin.

[Isolation of vacuoles from Candida tropicalis]

Intact vacuoles were isolated from the homogenate of the Candida tropicalis protoplasts by flotation in a stepwise gradient of phycoll density. New parameters of protoplast decomposition in hypotonic and isotonic conditions yielding intact vacuoles have been found, as well parameters of density gradient and conditions of centrifugation which differ essentially from parameters used by other authors for isolating the vacuoles from the Saccharomyces cells. The purity of the vacuole preparations was confirmed by using enzymes, light and electron microscopy. The specific content of the carbon of protein, lipids, and free amino acids in the vacuoles and protoplasts of the yeast cells cultivated on 14C-labelled glucose was determined by the radioindicator technique.

Susceptibility and resistance of Candida to 5-fluorocytosine in relation to the cell wall ultrastructure

Studies on the susceptibility of Candida albicans to 5-fluorocytosine (5FC) demonstrated a high rate of resistance (85%) for serogroup B strains, more frequently isolated in Africa, and a low incidence (<1%) for serogroup A, predominating among Whites (Drouhet et al., 1974). Determination of the electrophoretic mobility of various strains did not provide a correlation between the charged groups of the surface and their phenotype to 5FC and antigenic groups. Adsorption of the surface antigens with a hyperimmune antiserum did not modify the phenotypic expression of Candida to 5FC. Electron microscopy studies revealed that susceptible strains had an additional granular layer dividing the inner stratum into two parts. After trypsin digestion of these strains, the disappearance of this layer was concomitantly associated with the emergence of resistance. Thus, it appears that the cell wall contains a proteinic material, which is located in the interior of the electron-transparent region and acts in the metabolism of 5FC.

A comparative analysis of the ultrastructure of hydrocarbon-oxidizing micro-organisms

The ultrastructure of a variety of micro-organisms was compared after growth on hydrocarbon and non-hydrocarbon substrates. Hydrocarbon-grown organisms were characterized by the presence of intracellular electron-transparent inclusions which in many cases appeared membrane-bound. With one exception, non-hydrocarbon-grown organisms did not contain electron-transparent inclusions. Insignificant amounts of poly-beta-hydroxybutyric acid were produced by the hydrocarbon-grown micro-organisms. After growth on hydrocarbons, all the microorganisms had accumulated varying amounts of the respective unmodified hydrocarbon growth substrate.