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At least 19 recordsLinked to original sources
PubMed1975

Studies on tetrahymena membranes. Modification of surface membrane lipids by replacement of tetrahymanol by exogenous ergosterol in Tetrahymena pyriformis.

Tetrahymena pyriformis WH-14 cells were grown in the medium supplemented with ergosterol (1 mg/100 ml) and the effects of replacement of tetrahymanol by ergosterol upon the lipid composition in the surface membranes (cilia and pellicles) were examined. 1. By scanning and freeze-etch electron microscopy it was suggested that exogenous ergosterol would be inserted into the lipid regions in the surface membranes. Although freeze-etched faces of filipin-treated membranes containing the native tetrahymanol showed a random distribution of 85-a protein particles, the ergosterol-replaced membranes after the same polyene treatment revealed the marked ultrastructural alterations on the fracture faces. 2. The replacement of tetrahymanol in membranes by ergosterol induced a profound alteration in the phospholipid class composition and a marked increase in phosphatidylethanolamine with a compensatory decrease in phosphatidylcholine and 2-aminoethylphosphonolipid. 3. There are significant and quantitative but not qualitative changes in the fatty acid composition of total lipids from the ergosterol-replaced membranes. There are also increases in saturated and decreases in unsaturated fatty acids. Phosphatidylethanolamine acyl chains particularly become more saturated, as compared with two other phospholipids, in ergosterol-replaced pellicles. This increase in saturation is due to an appreciable increase in C14:0, C16:0 and iso-C17:0, and a decrease in C18:1(delta9), C18:2(delta9,12) and C18:3(delta6,9,12). 4. These results suggest that profound alterations in phospholipids as well as in their fatty acyl chains are required to modify the overall membrane lipid composition for the maintenance of proper membrane fluidity. Our data would also support the thesis that polat head groups are involved in the membrane lipid organization and that sterols interact selectively with phospholipid molecules containing the appropriate fatty acyl chain composition in biological membranes.

Acetates↗
PubMed1992

[Cold storage of wheat. 1. Ergosterol, ochratoxin A and citrinin after inoculation with Penicillium verrucosum].

Seed wheat was inoculated without having been sterilized with an ochratoxin A and citrinin forming strain of Penicillium verrucosum and stored at moisture contents of 18, 20, 22, 24, and 26% at 10 and 4 degrees C. The production of ergosterol, a chemical indicator of fungal biomass, started within the storage time investigated (240 days). Only at 18% H2O/4 degrees C an increase of the ergosterol content was not observed. Ochratoxin A and Citrinin were not detected at 18% H2O/4 degrees C and 20% H2O/4 degrees C within 240 days (detection limit: 10 and 25 micrograms/kg, respectively). At the other combinations of moisture content and temperature the first detection of the two toxins approximately coincided with the onset of ergosterol production. With increasing moisture content and temperature the time up to the start of ergosterol production decreased, whereas the production rates of ergosterol, ochratoxin A and citrinin increased. Both toxins were produced with about the same rate during a first phase of accumulation. At 20-26% H2O there was no influence of moisture content and temperature on the relation between toxin content and the simultaneously reached ergosterol content. It is recommended that wheat highly contaminated with Penicillium verrucosum should not be stored beyond the start of ergosterol production.

Citrinin↗
PubMed1979

The effect of altered ergosterol content on the transport of various amino acids in Candida albicans.

Candida albicans cells have low levels of ergosterol when grown in ascorbic acid-supplemented media. When cells are grown in hydroquinone-supplemented media, the ergosterol levels became higher as compared to normal cells. The uptake of lysine, glycine, glutamic acid, proline, methionine and serine is reduced in hydroquinone-supplemented cells. In contrast to hydroquinone-supplemented cells, the rate and level of accumulation of these amino acids are higher in ascorbic acid-supplemented cells. Nystatin-resistant isolates of C. albicans with low ergosterol contents also exhibit an increased rate and level of accumulation of these amino acids. The uptake of phenylalanine and leucine remained unaffected by such a change in ergosterol levels brought about by different supplementation of the media. The results demonstrate a correlation between ergosterol levels and amino acids uptake. Contrary to various reports, the rate of K+ efflux does not seem to correlate with the amino acid uptake in C. albicans cells.

Amino Acids↗
PubMedDate not supplied

[Ergosterol synthesis by hybrids and strains of yeasts of the genus saccharomyces with different ploidies].

Numerous hybrid and polyploid strains of the Saccharomyces genus were obtained by hybridization. The activity of ergosterol synthesis was assayed in hybrids, several industrial races, and in haploid and diploid cultures produced from the spores of these races. The content of ergosterol was determined in 160 strains and hybrids. Ergosterol synthesis is controlled by recessive genes, and accumulation of ergosterol in the cell depends on the interaction between genes. During growth in semiindustrial conditions, triploid hybrids accumulated more biomass than diploid, and particularly haploid, strains. Polyploid hybrids valuable for food industry have been selected, according to several characteristics, from active hybrid strains. One of them, the triploid 262, is characterized by a high rate of ergosterol synthesis, good baking quality, and resistance to dehydration.

Ergosterol↗
PubMed1977

Determination of the absolute configuration at C-20 and C-24 of ergosterol in Ascomycetes and Basidiomycetes by proton magnetic resonance spectroscopy.

Samples of ergosterol isolated from Saccharomyces cerevisiae, Neurospora crassa, and Agaricus sp., and commercial ergosterol all displayed identical proton magnetic resonance (PMR) spectra at 220 MHz. From the effects produced on the doublet for C-21 by epimerization at C-20 and C-24 in sterols of known configuration, the absolute configurations at these positions in ergosterol were determined. The data demonstrate that ergosterol from both Ascomycetes and Basidiomycetes is the same and that at C-20 and C-24, the two H-atoms are on the alpha-side of the asymmetric carbon atoms and that C-22 is trans-oriented with respect to C-13 about the 17(20)-bond.

Ascomycota↗
PubMed1979

Differential biosynthesis of polyunsaturated fatty acids by Tetrahymena supplemented with ergosterol.

Tetrahymena grown with foreign sterols such as ergosterol incorporate them into cellular membranes at the expense of the native compound, tetrahymanol. It is shown that cells grown with ergosterol have a lessened capacity to produce the polyunsaturated linoleic and gamma-linolenic acids from [14C]oleic acid. However, the same cells have normal capacities to introduce double bonds at C-6 into linoleate, alpha-linolenate, or cis-vaccenate. Thus, a presumed 12-desaturase is inhibited in the presence of ergosterol, while desaturation at C-6 is unaffected.

Ergosterol↗
PubMed1978

Ergosterol biosynthesis in yeast. Pathways in the late stages and their variation under various conditions.

[Methyl-14C]methionine was supplied to yeast cells under aerobic and anaerobic conditions for the investigation of the pathway for ergosterol biosynthesis after the methylation of the side-chain. Under aerobic conditions, the incorporation of radioactivity into ergosterol was high. With a limited oxygen supply, in contrast, the radioactivity was first accumulated in ergosta-7,24(28)-dien-3beta-ol and ergosta-8,24(28)-dien-3beta-ol, and then transferred to ergost-7-en-3beta-ol, ergost-8-en-3beta-ol and ergosta-7,22-dien-3beta-ol with time. Under strictly anaerobic conditions, a double bond was introduced neither to delta5 nor to delta22. The results of the tracer experiments suggested the operation of several pathways in the late stages of ergosterol biosynthesis. It was also suggested that the main pathways varied depending on the conditions such as oxygen supply and other factors. The above conclusion was supported by the results of the analyses of the sterol compositions of the cells grown under various conditions.

Aerobiosis↗
PubMed1975

Nuclear demethylation and C-24 alkylation during ergosterol biosynthesis in Saccharomyces cerevisiae.

The role of 4,4-dimethylzymosterol (3), 4,4-dimethylfecosterol (4) and 31-norlanosterol (5) in the biosynthesis of ergosterol in Saccharomyces cerevisiae has been investigated. The synthesis of 4 and 5 coupled with the availability of 3 facilitated a search for these sterols in commercial yeast sterol concentrates, fresh laboratory grown yeast and fresh brewery grown yeast. Sterol 4 was not detected in any of these mixtures whereas 5 was found in the first and last and 3 was present in all three sources investigated. Investigation of incorporation of [2-3H]lanosterol into 3, 4 and 5 revealed significant incorporation into 3 but neither 4 nor 5. This observation suggests the principle pathway for ergosterol biosynthesis initially involved 1 leads to 3 leads to 7. Incubation of a mixture of [2,4-3H]zymosterol and [26,27-14C]lanosterol with S. cerevisiae revealed that during the initial phases of aerobic growth the major route from 7 to ergosterol involves zymosterol (11) but as 11 accumulates 4 alpha-methyl-24-methylenezymosterol (8) assumes equal importance.

Chromatography, Gas↗
PubMedDate not supplied

[Formation of ergosterol by yeasts of Candida genus].

The formation of ergosterol by the Candida yeast was studied using glucose, n-paraffins, a mixture of organic acids and inedible sugars. Yeast of different species and strains showed a similar content of ergosterol which made, as a rule, 0.4--0.5%. The amount of ergosterol remained relatively stable with varying cultivation conditions and decreased 1.5--2 times with a temperature increase.

Alkanes↗
PubMedDate not supplied

[A spectroscopic examination on intermolecular interaction of ergosterol with lecithin].

The ergosterol and lecithin absorption IR-spectra were studied in a nonpolar anhydrous medium. The thermodynamical and spectral characteristics of dimeric associates and the enthalpy value for trimeric associates of this sterol are determined. Thermodynamical and spectral parameters of ergosterol intermolecular associates with lecithin in a nonpolar anhydrous medium are found. It is established that the intermolecular interaction of lecithin with ergosterol occurs according to the mechanism of hydrogen bond. A conclusion is drawn that the presence of binary bonds and methyl groups in the cyclic and aliphatic parts of the sterol molecule affects greatly the structure of the model membrane and its strength. It is shown that under conditions of the experiment the oxygen of the phosphate group contributes to formation of the molecular associates of lecithin with sterols and not that of the carbonyl group. The obtained experimental data may be at use when studying structural disturbances of native membranes in norm and with different pathologies.

Chemical Phenomena↗
PubMed2025

Ergosterol-depleted clinical isolates of Nakaseomyces glabratus can develop multi-drug resistance without apparent fitness and virulence defects.

OBJECTIVES: Nakaseomyces glabratus (formerly Candida glabrata) is a leading cause of invasive candidiasis and rapidly develops antifungal drug resistance during treatment. An increasing number of clinical isolates shows reduced susceptibility to echinocandins and azoles, leaving amphotericin B (AMB) as a last therapeutic option. Resistance of N. glabratus to this drug is rare and its underlying mechanisms are still not fully understood. Here, we describe two independent multidrug resistant (MDR) bloodstream isolates displaying resistance to AMB and anidulafungin (ANF) as well as a reduced susceptibility to azoles. METHODS: Whole-genome sequencing and sterol profiling were performed on nine clinical N. glabratus isolates which were resistant to ANF and displayed resistance or low susceptibility to fluconazole (FLU) and AMB. The transcriptional response of reference strain CBS138 and an AMBR+ANFR isolate was analyzed by RNA-seq. Furthermore, PDR1 was deleted in the latter isolate to examine its influence on efflux pump gene expression. Additionally, fitness and virulence of the AMBR+ANFR isolate were examined in growth assays and a Galleria mellonella infection model. RESULTS: Loss of function mutations in the genes ERG3 and ERG4 is linked to ergosterol depletion and AMB resistance. Ergosterol depletion also contributed to a Pdr1-mediated up-regulation of ERG and ABC transporter genes which was associated with low FLU susceptibility. The AMBR isolates displayed no fitness defects and one of them was fully virulent in a G. mellonella infection model. CONCLUSIONS: These findings demonstrate that ergosterol depletion in N. glabratus leads to AMB resistance without affecting fitness or virulence.

Journal Article↗
PubMed1979

Effects of lipid-phase separation on the filipin action on membranes of ergosterol-replaced Tetrahymena cells, as studied by freeze-fracture electron microscopy.

The effects of lipid-phase separation on the filipin action on pellicle membranes of ergosterol-replaced Tetrahymena pyriformis cells were studied by freeze-fracture electron microscopy. The pellicle membranes with phase separations induced by chilling from 34 degrees C (growth temperature) to lower temperatures (30, 22 and 15 degrees C) were treated with filipin. This produced filipin-induced lesions ("pits") only in the particulated (liquid) regions along the margin between solid and liquid domains, while they were produced in the particle-free (solid) areas when membranes were chilled to 15 degrees C. The pellicle membranes with lesions induced by filipin at 34 degrees C were chilled to 22 degrees C. This chilling raised larger particle-free areas and more condensed particle-aggregations on the membranes than on the membranes without the filipin treatment. These results suggest that the membrane fluidity affects induction and development of the ergosterol-filipin complex in the membrane.

Animals↗
PubMed1992

Ergosterol levels in two L-methionine-enriched mutants of the methylotrophic yeast Candida boidinii ICCF26.

Two L-methionine-enriched mutants, SN-78 and SE-57, were isolated in a sulphur-deficient medium from the methylotrophic yeast Candida boidinii ICCF26. No significant differences were detected between the L-cysteine pools of the mutants and the wild-type. In mutant strain SE-57, S-adenosylmethionine and ergosterol levels were higher than in the wild-type strain, while in the other mutant, SN-78, the levels were lower. The evidence presented would suggest that, in both the mutants and the wild-type used in this study, S-adenosylmethionine was of key importance for the accumulation of L-methionine and ergosterol.

Candida↗
PubMed1977

The effects of ergosterol on the response of female chicks to oral oestrogens and progestogens.

The chick-oviduct assay was used to investigate the effects of dietary ergosterol on the response to oral progestogens and oestrogens. 2. Progestogens alone had no effect on the oviduct but the hypertrophy due to oestrogen was greatly enhanced by simultaneous treatment with progestogen at all dose levels tested. 3. Ergosterol had no effect on any of the responses of the oviduct studied.

Animals↗
PubMed1975

Oxygen pressure, fatty acid composition and ergosterol level in Rhodotorula gracilis.

Cells of Rhodotorula gracilis grown for 6 hrs at 2 mm Hg O2 pressure when compared with cells grown for 6 hrs at 140 mm Hg, show: a) a large decrease in the level of ergosterol, b) a significant increase in the level of oleic acid and a decrease in the levels of linoleic and linolenic acids, both in fatty acid fraction of the phospholipids and in the free fatty acids and neutral fat fractions. The results suggest that the dehydrogenation of oleic acid to linoleic acid is preferentially inhibited at low O2 pressure. The possibility is considered that these changes of lipid metabolism might be causally related with decrease of the growth rate observed at low O2 pressure.

Ergosterol↗
PubMed1992

Ergosterol depletion and 4-methyl sterols accumulation in the yeast Saccharomyces cerevisiae treated with an antifungal, 6-amino-2-n-pentylthiobenzothiazole.

In Saccharomyces cerevisiae treated with an antifungal agent, 6-amino-2-n-pentylthiobenzothiazole, levels of ergosterol and other 4-desmethylsterols were found to be significantly reduced. Major sterols in treated yeast were lanosterol, 4,4-dimethylzymosterol, 4-methylzymosterol and 4-methylfecosterol. A hypothesis is stated that the antifungal agent inhibits sterol demethylation at C-4 and forces the biosynthesis to a blind pathway ending by 4-methylfecosterol.

Antifungal Agents↗