A high intracellular concentration of potassium (200-300 mmol/L) is essential for many yeast cell functions, such as the regulation of cell volume and pH, maintenance of membrane potential, and enzyme activation. Thus, cells use high-affinity specific transporters and expend a lot of energy to acquire the necessary amount of potassium from their environment. In Candida genomes, genes encoding 3 types of putative potassium uptake systems were identified: Trk uniporters, Hak symporters, and Acu ATPases. Tests of the tolerance and sensitivity of C. albicans, C. dubliniensis, C. glabrata, C. krusei, C. parapsilosis, and C. tropicalis to various concentrations of potassium showed significant differences among the species, and these differences were partly dependent on external pH. The species most tolerant to potassium-limiting conditions were C. albicans and C. krusei, while C. parapsilosis tolerated the highest KCl concentrations. Also, the morphology of cells changed with the amount of potassium available, with C. krusei and C. tropicalis being the most influenced. Taken together, our results confirm potassium uptake and accumulation as important factors for Candida cell growth and suggest that the sole (and thus probably indispensable) Trk1 potassium uptake system in C. krusei and C. glabrata may serve as a target for the development of new antifungal drugs.
- Klíčová slova
- Candida, homéostasie du potassium, morphologie, morphology, potassium homeostasis,
- MeSH
- Candida albicans růst a vývoj patogenita MeSH
- Candida glabrata růst a vývoj patogenita MeSH
- Candida tropicalis růst a vývoj patogenita MeSH
- Candida růst a vývoj patogenita MeSH
- draslík metabolismus MeSH
- genom fungální MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- draslík MeSH
A defined mixed culture of Pseudomonas putida, Commamonas testosteroni and Candida tropicalis was immobilized by adsorption on polyurethane foam, cocoa-fibers, expanded slate and sintered glass. Packed bed reactors were used for long-term continuous phenol biodegradations. Loading experiments were done to study the impact of the following parameters: (1) hydraulic retention time, (2) dissolved oxygen concentration, and (3) elimination of the oxygen limitation. After the acclimation period (approximately 10 d), the loading test with the individual packings showed the following maximum degradation rates: sintered glass 34, polyurethane foam 12, expanded slate 11.5, and cocoa-fibers 7.7 kg m(-3) d(-1). All these values were reached at a removal efficiency >99 % and with oxygen in excess. Under these conditions, the pH of the diluted unbuffered medium in the reactor effluent was 3.2-4.0 and no incompletely oxidized metabolic intermediates were found. The free cell concentration in the effluent increased after the phenol overloading time period.
- MeSH
- aerobióza MeSH
- biodegradace MeSH
- bioreaktory * MeSH
- biotechnologie metody MeSH
- Candida tropicalis růst a vývoj metabolismus MeSH
- ekosystém * MeSH
- fenol metabolismus MeSH
- gramnegativní bakterie genetika růst a vývoj MeSH
- imobilizované buňky MeSH
- kultivační média MeSH
- Pseudomonas putida růst a vývoj metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
- Názvy látek
- fenol MeSH
- kultivační média MeSH
Microsomal preparations isolated from yeast Candida tropicalis (C. tropicalis) grown on three different media with or without phenol were isolated and characterized for the content of cytochrome P450 (CYP) (EC 1.14.15.1). While no CYP was detected in microsomes of C. tropicalis grown on glucose as the carbon source, evidence was obtained for the presence of the enzyme in the microsomes of C. tropicalis grown on media containing phenol. Furthermore, the activity of NADPH: CYP reductase, another enzyme of the microsomal CYP-dependent system, was markedly higher in cells grown on phenol. Microsomes of these cells oxidized phenol. The major metabolite formed from phenol by microsomes of C. tropicalis was characterized by UV/vis absorbance and mass spectroscopy as well as by the chromatographic properties on HPLC. The characteristics are identical to those of catechol. The formation of catechol was inhibited by CO, the inhibitor of CYP, and correlated with the content of cytochrome P450 in microsomes. These results, the first report showing the ring hydroxylation of phenol to catechol with the microsomal enzyme system of C. tropicalis, strongly suggest that CYP-catalyzed reactions are responsible for this hydroxylation. The data demonstrate the progress in resolving the enzymes responsible for the first step of phenol degradation by the C. tropicalis strain.
- MeSH
- biodegradace MeSH
- Candida tropicalis enzymologie růst a vývoj MeSH
- chemické látky znečišťující vodu metabolismus MeSH
- čištění vody metody MeSH
- fenol metabolismus MeSH
- hydroxylace MeSH
- katecholy metabolismus MeSH
- koenzymy metabolismus MeSH
- mikrozomy enzymologie MeSH
- průmyslový odpad prevence a kontrola MeSH
- systém (enzymů) cytochromů P-450 metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- catechol MeSH Prohlížeč
- chemické látky znečišťující vodu MeSH
- fenol MeSH
- katecholy MeSH
- koenzymy MeSH
- průmyslový odpad MeSH
- systém (enzymů) cytochromů P-450 MeSH
