Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 6 de 6
Filter
Add more filters










Database
Language
Publication year range
1.
J Bioenerg Biomembr ; 45(6): 561-8, 2013 Dec.
Article in English | MEDLINE | ID: mdl-24052423

ABSTRACT

Recently we introduced a fluorescent probe technique that makes possible to convert changes of equilibrium fluorescence spectra of 3,3'-dipropylthiadicarbocyanine, diS-C3(3), measured in yeast cell suspensions under defined conditions into underlying membrane potential differences, scaled in millivolts (Plasek et al. in J Bioenerg Biomembr 44: 559-569, 2012). The results presented in this paper disclose measurements of real early changes of plasma membrane potential induced by the increase of extracellular K(+), Na(+) and H(+) concentration in S. cerevisiae with and without added glucose as energy source. Whereas the wild type and the ∆tok1 mutant cells exhibited similar depolarization curves, mutant cells lacking the two Trk1,2 potassium transporters revealed a significantly decreased membrane depolarization by K(+), particularly at lower extracellular potassium concentration [K(+)]out. In the absence of external energy source plasma membrane depolarization by K(+) was almost linear. In the presence of glucose the depolarization curves exhibited an exponential character with increasing [K(+)]out. The plasma membrane depolarization by Na(+) was independent from the presence of Trk1,2 transporters. Contrary to K(+), Na(+) depolarized the plasma membrane stronger in the presence of glucose than in its absence. The pH induced depolarization exhibited a fairly linear relationship between the membrane potential and the pHo of cell suspensions, both in the wild type and the Δtrk1,2 mutant strains, when cells were energized by glucose. In the absence of glucose the depolarization curves showed a biphasic character with enhanced depolarization at lower pHo values.


Subject(s)
Hydrogen/metabolism , Potassium/metabolism , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/metabolism , Sodium/metabolism , Cations, Monovalent/metabolism , Cell Membrane/metabolism , Fluorescent Dyes/chemistry , Fluorometry , Hydrogen-Ion Concentration , Membrane Potentials/drug effects
2.
J Bioenerg Biomembr ; 44(5): 559-69, 2012 Oct.
Article in English | MEDLINE | ID: mdl-22810564

ABSTRACT

The fluorescent dye 3,3'-dipropylthiadicarbocyanine, diS-C(3)(3), is a suitable probe to monitor real changes of plasma membrane potential in yeast cells which are too small for direct membrane potential measurements with microelectrodes. A method presented in this paper makes it possible to convert changes of equilibrium diS-C(3)(3) fluorescence spectra, measured in yeast cell suspensions under certain defined conditions, into underlying membrane potential differences, scaled in the units of millivolts. Spectral analysis of synchronously scanned diS-C(3)(3) fluorescence allows to assess the amount of dye accumulated in cells without otherwise necessary sample taking and following separation of cells from the medium. Moreover, membrane potential changes can be quantified without demanding calibration protocols. The applicability of this approach was demonstrated on the depolarization of Rhodotorula glutinis yeast cells upon acidification of cell suspensions and/or by increasing extracellular K(+) concentration.


Subject(s)
Carbocyanines/chemistry , Fluorescent Dyes/chemistry , Membrane Potentials/physiology , Rhodotorula/physiology , Rhodotorula/cytology
3.
FEMS Microbiol Lett ; 254(2): 240-4, 2006 Jan.
Article in English | MEDLINE | ID: mdl-16445751

ABSTRACT

The expression of the Tvsrh1 gene encoding conidial hydrophobin was investigated during the development of surface-cultivated Trichoderma viride mycelia under different illumination regimes. Three transcripts of the whole gene amplified from the total mRNA were found with lengths of 400, 323 and 272 bp. The 400-bp transcript was slowly converted to the shorter forms in the dark. Light-pulse dramatically increased the rate of conversion, and a permanent illumination of mycelia was most efficient in this process. The sequencing of transcripts revealed that the 400 bp transcript contains two introns, whereas the intermediate one contains only one intron located distally from the 5'-end. The shortest transcript was without introns. The sum of all transcripts remained almost unchanged in the dark and increased upon the light pulse but decreased during development under permanent illumination. The appearance of conidia coincided with the complete conversion of the transcripts. The results showed that the splicing of the two introns was not random but sequential, and that it did not follow the cotranscriptional mechanism. Furthermore, they suggested that mRNA processing could represent another regulation level of gene expression by light during the photo-induced conidiation in T. viride.


Subject(s)
Fungal Proteins/metabolism , Gene Expression Regulation, Fungal , Light , Mycelium/metabolism , RNA Splicing , Trichoderma/metabolism , Base Sequence , Fungal Proteins/chemistry , Fungal Proteins/genetics , Molecular Sequence Data , Mycelium/genetics , Sequence Analysis, DNA , Transcription, Genetic , Trichoderma/genetics , Trichoderma/growth & development
4.
Antonie Van Leeuwenhoek ; 88(3-4): 267-75, 2005.
Article in English | MEDLINE | ID: mdl-16284933

ABSTRACT

Based on morphological characteristics the taxa included in the Aspergillus aggregate can hardly be differentiated. For that reason the phylogeny of this genus was revised several times as different criteria, from morphological to later molecular, were used. We found, comparing nucleotide sequences of the ITS-region, that the strain Aspergillus niger (DSM 823) which is claimed to be identical to the strains ATCC 10577, IMI 027809, NCTC 7193 and NRRL 2322 can be molecularly classified as Aspergillus tubingensis, exhibiting 100% identity with the A. tubingensis CBS strains 643.92 and 127.49. We amplified, cloned and sequenced a new glucoamylase gene (glaA) from this strain of A. tubingensis (A. niger DSM 823) using primers derived from A. niger glucoamylase G1. The amplified cDNA fragment of 2013 bp contained an open reading frame encoding 648 amino acid residues. The calculated molecular mass of the glucoamylase, deduced from the amino acid sequence, was 68 kDa. The nucleotide sequence of glaA showed 99% similarity with glucoamylases from Aspergillus kawachii and Aspergillus shirousami, whereas the similarity with the glucoamylase G1 from A. niger was 92%


Subject(s)
Aspergillus niger/classification , Aspergillus niger/enzymology , Glucan 1,4-alpha-Glucosidase/genetics , Amino Acid Sequence , Aspergillus niger/genetics , Base Sequence , Cloning, Molecular , DNA, Fungal/chemistry , DNA, Fungal/genetics , DNA, Ribosomal Spacer/chemistry , DNA, Ribosomal Spacer/genetics , Genes, Fungal , Glucan 1,4-alpha-Glucosidase/chemistry , Molecular Sequence Data , Molecular Weight , Open Reading Frames , Phylogeny , Sequence Analysis, DNA , Sequence Homology, Amino Acid
5.
Res Microbiol ; 156(9): 932-43, 2005 Nov.
Article in English | MEDLINE | ID: mdl-16085397

ABSTRACT

Microorganisms were isolated from lignite freshly excavated in the Záhorie coal mine (southwestern Slovakia) under conditions excluding contamination with either soil or air-borne microorganisms. The isolates represented both Prokarya and Eukarya (fungi). All were able to grow on standard media, although some microorganisms were unstable and became extinct during storage of coal samples. Bacteria belonged to the genera Bacillus, Staphylococcus, and Rhodococcus, according to both morphological criteria and ITS sequences. Several bacterial isolates were resistant to antibiotics. The presence of anaerobic bacteria was also documented, although they have not yet been identified. Fungal isolates were typified by using their ITS sequences. They belonged to the genera Trichoderma (Hypocrea), Penicillium, Epicoccum, Metarhizium (Cordyceps), and Cladosporium. Several fungi produced compounds with antibiotic action against standard bacterial strains. The evidence for the presence of microorganisms in native lignite was obtained by means of fluorescence microscopy, scanning electron microscopy, and electron microprobe analysis. Results demonstrated that microorganisms were able to survive in the low-rank coal over a long time period.


Subject(s)
Bacteria/classification , Bacteria/isolation & purification , Coal/microbiology , Fungi/classification , Fungi/isolation & purification , Mining , Anti-Bacterial Agents/biosynthesis , Anti-Bacterial Agents/pharmacology , Antibiosis , Bacillus/classification , Bacillus/isolation & purification , Bacteria, Anaerobic/isolation & purification , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , DNA, Ribosomal Spacer/chemistry , DNA, Ribosomal Spacer/genetics , Drug Resistance, Microbial , Electron Probe Microanalysis , Microscopy, Electron, Scanning , Microscopy, Fluorescence , Molecular Sequence Data , Rhodococcus/classification , Rhodococcus/isolation & purification , Sequence Analysis, DNA , Slovakia , Staphylococcus/classification , Staphylococcus/isolation & purification
6.
Antonie Van Leeuwenhoek ; 86(4): 287-94, 2004 Nov.
Article in English | MEDLINE | ID: mdl-15704285

ABSTRACT

A hitherto undescribed black yeast was isolated from an extract of brown coal containing humic and fulvic acids at pH 0.6. The fungus showed morphological similarity to some members of the genus Exophiala (Chaetothyriales) and of Hortaea (Dothideales). Based on SSU rDNA sequence similarity to meristematic members of the Dothideales, the new species was accommodated in Hortaea, which presently contains only a single, halophilic species, H. werneckii.


Subject(s)
Acids/pharmacology , Ascomycota/drug effects , Coal , Ascomycota/classification , Ascomycota/genetics , Ascomycota/growth & development , Carbon/metabolism , DNA, Ribosomal/genetics , DNA, Ribosomal/isolation & purification , Drug Resistance, Fungal , Phylogeny
SELECTION OF CITATIONS
SEARCH DETAIL
...