Pavla Češková

Kinetic constant variability in bacterial oxidation of elemental sulfur

ABSTRACT Wide ranges of growth yields on sulfur (from 2.4 × 1010 to 8.1 × 1011 cells g−1) and maximum sulfur oxidation rates (from 0.068 to 1.30 mmol liter−1 h−1) of an Acidithiobacillus ferrooxidans strain (CCM 4253) were observed in 73 batch cultures. No significant correlation between the constants was observed. Changes of the Michaelis constant for sulfur (from 0.46 to 15.5 mM) in resting cells were also noted.

Determination of rhodanese enzyme activity by capillary zone electrophoresis

A new sensitive method has been developed for the determination of rhodanese activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of SCN- was monitored by sequential capillary zone electrophoretic runs. The determinations were performed in a 75-micron fused-silica capillary using 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, a separation voltage of 18 kV (negative polarity), a capillary temperature of 25 degrees C and direct detection at 200 nm. Short-end injection or long-end injection procedures were used for sample application. The method is rapid, able to be automated and requires only small amounts of sample and substrates, which is especially important in the case of highly toxic cyanide. The developed capillary electrophoretic method also has great potential for thiocyanate determinations in other applications.

Metabolic activity of Thiobacillus ferrooxidans on reduced sulfur compounds detected by capillary isotachophoresis

Abstract The sulfur-oxidizing activity of Thiobacillus ferrooxidans was investigated using capillary isotachophoresis. The oxidation of pyrite and sulfur was detected through sulfate formation while oxidation of thiosulfate was detected by thiosulfate consumption. Electrolyte systems and the conditions for the isotachophoretic determination of sulfate (leading electrolyte: HCl, 1 mmol l −1 ; CaCl 2 , 2 mmol l −1 and β -alanine, pH 4.0; terminating electrolyte: citric acid, 1 mmol l −1 ) and thiosulfate (leading electrolyte: HCl, 1 mmol l −1 ; CaCl 2 , 4 mmol l −1 and β -alanine; terminating electrolyte: hexanoic acid, 5 mmol l −1 ) are described. Oxidation of pyrite and sulfur occurred without sulfur intermediate formation; however, during thiosulfate oxidation, sulfur intermediates were detected.

The cell type-specific effect of TAp73 isoforms on the cell cycle and apoptosis

Abstractp73, a member of the p53 family, exhibits activities similar to those of p53, including the ability to induce growth arrest and apoptosis. p73 influences chemotherapeutic responses in human cancer patients, in association with p53. Alternative splicing of the TP73 gene produces many p73 C- and N-terminal isoforms, which vary in their transcriptional activity towards p53-responsive promoters. In this paper, we show that the C-terminal spliced isoforms of the p73 protein differ in their DNA-binding capacity, but this is not an accurate predictor of transcriptional activity. In different p53-null cell lines, p73β induces either mitochondrial-associated or death receptor-mediated apoptosis, and these differences are reflected in different gene expression profiles. In addition, p73 induces cell cycle arrest and p21WAF1 expression in H1299 cells, but not in Saos-2. This data shows that TAp73 isoforms act differently depending on the tumour cell background, and have important implications for p73-mediated therapeutic responses in individual human cancer patients.

Kinetic quantitation of sulfur-oxidizing bacteria adsorbed on sulfur

A hyperbolic equation was fitted to the time dependence of Thiobacillus ferrooxidans adsorption on sulfur. This procedure allowed the determination of an asymptote value which represented a free cell count at equilibrium. The data thus obtained were used to calculate the numbers of adsorbed bacteria without attainment of equilibrium. The maximum number of adsorbed bacteria based on the Langmuir isotherm was 8.3 × 109 per g of sulfur.

Formation of iodinin by a strain of Acidithiobacillus ferrooxidans grown on elemental sulfur

The presence of the pigment iodinin, anAcidithiobacillus ferrooxidans culture metabolite, was demonstrated after growth of bacteria on elemental sulfur. The structure of iodinin was confirmed by X-ray structure analysis; its physiological role is discussed.