Genomic, transcriptomic and physiological analyses of silver-resistant Saccharomyces cerevisiae obtained by evolutionary engineering.

Silver is a non-essential metal used in medical applications as an antimicrobial agent, but it is also toxic for biological systems. To investigate the molecular basis of silver resistance in yeast, we employed evolutionary engineering using successive batch cultures at gradually increased silver stress levels up to 0.25-mM AgNO3 in 29 populations and obtained highly silver-resistant and genetically stable Saccharomyces cerevisiae strains. Cross-resistance analysis results indicated that the silver-resistant mutants also gained resistance against copper and oxidative stress. Growth physiological analysis results revealed that the highly silver-resistant evolved strain 2E was not significantly inhibited by silver stress, unlike the reference strain. Genomic and transcriptomic analysis results revealed that there were mutations and/or significant changes in the expression levels of the genes involved in cell wall integrity, cellular respiration, oxidative metabolism, copper homeostasis, endocytosis and vesicular transport activities. Particularly the missense mutation in the RLM1 gene encoding a transcription factor involved in the maintenance of cell wall integrity and with 707 potential gene targets might have a key role in the high silver resistance of 2E, along with its improved cell wall integrity, as confirmed by the lyticase sensitivity assay results. In conclusion, the comparative physiological, transcriptomic and genomic analysis results of the silver-resistant S. cerevisiae strain revealed potential key factors that will help understand the complex molecular mechanisms of silver resistance in yeast.

Determination of lead, cadmium and nickel in hennas and other hair dyes sold in Turkey.

The concentrations of lead, nickel and cadmium in various hennas and synthetic hair dyes were determined by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). For this purpose, 1 g of sample was digested using 4 mL of hydrogen peroxide (30%) and 8 mL of nitric acid (65%). The digests were diluted to 15 mL and the analytes were determined by HR-CS GFAAS. All determinations of Pb and Cd were performed using NH4H2PO4 as a modifier. The analytes in hair certified reference materials (CRMs) were found within the uncertainty limits of the certified values. In addition, the analyte concentrations added to hair dye were recovered between 95 and 110%. The limits of detection of the method were 48.90, 3.90 and 12.15 ng g(-1) for Pb, Cd and Ni, respectively and the characteristic concentrations were 8.70, 1.42 and 6.30 ng g(-1), respectively. Finally, the concentrations of the three analytes in various synthetic hair dyes with different brands, shades and formulae as well as in two henna varieties were determined using aqueous standards for calibration. The concentrations of Pb, Cd and Ni in hair dyes were in the ranges of LOD-0.56 µg g(-1), LOD-0.011 ng g(-1) and 0.030-0.37 µg g(-1), respectively, whereas those in the two hennas were 0.60-0.93 µg g(-1), 0.033-0.065 ng g(-1) and 0.49-1.06 µg g(-1), respectively.

Evolutionary engineering and transcriptomic analysis of nickel-resistant Saccharomyces cerevisiae.

Increased exposure to nickel compounds and alloys due to industrial development has resulted in nickel pollution and many pathological effects on human health. However, there is very limited information about nickel response, transport, and tolerance in eukaryotes. To investigate nickel resistance in the model eukaryote Saccharomyces cerevisiae, evolutionary engineering by batch selection under gradually increasing nickel stress levels was performed. Nickel hyper-resistant mutants that could resist up to 5.3 mM NiCl2 , a lethal level for the reference strain, were selected. The mutants were also cross-resistant against iron, cobalt, zinc, and manganese stresses and accumulated more than twofold higher nickel than the reference strain. Global transcriptomic analysis revealed that 640 upregulated genes were related to iron homeostasis, stress response, and oxidative damage, implying that nickel resistance may share common mechanisms with iron and cobalt resistance, general stress response, and oxidative damage.

Investigation of lead contents in lipsticks by solid sampling high resolution continuum source electrothermal atomic absorption spectrometry.

In this study, the lead contents of different kinds of lipsticks were determined by solid sampling high resolution continuum source electrothermal atomic absorption spectrometry (SS-HR-CS ET AAS) and the results were compared with those obtained after microwave-assisted acid digestion of the samples. The experimental parameters for solid sampling such as the maximum amount of sample on the platforms of solid autosampler, graphite furnace program were optimized. Samples were directly loaded on the platforms of solid autosampler between 0.25 and 2.0mg and lead was determined applying 800 °C for pyrolysis and 2100 °C for atomization. Under optimized conditions, interference-free determination could be performed using aqueous standards. The LOD and the characteristic mass were 21.3 and 12.6 pg, respectively. The lead in the same lipstick samples was determined after microwave-assisted acid digestion and compared with those found by solid sampling. Mostly, there was no significant difference between the lead concentrations found by the two techniques. The lead in 25 lipstick samples with different properties were 0.11-4.48 ng mg(-1) which were not significantly different from those (<0.026-7.19 ng mg(-1)) reported by FDA for around 400 samples.

In vivo evolutionary engineering of a boron-resistant bacterium: Bacillus boroniphilus.

Boron is an industrially and biologically important element. However, the mechanisms of boron tolerance and its transport in bacteria and many other living systems are still not clearly understood. In this study, the boron resistance level of a boron-tolerant bacterium, Bacillus boroniphilus DSM 17376, was improved up to 300 mmol l(-1) boron, by employing an in vivo evolutionary engineering strategy based on batch selection under continuous exposure to gradually increasing boron stress levels. The resistance was heterogeneous within the final mutant population which ranged from about 1- to 16-fold of the wild type resistance at 150 mmol l(-1) boron stress level. Boron-resistant mutants had significant cross-resistance to iron and copper stresses, and were also cross-resistant to salt (NaCl) stress, suggesting a common resistance mechanism between these stress types. Additionally, highly boron-resistant mutants had up to 2.8-fold higher boron contents than the wild-type, when exposed to high levels of (150 mmol l(-1)) continuous boron stress throughout their cultivation. It was shown that evolutionary engineering is a successful approach to significantly increase bacterial boron resistance and investigate the complex mechanism of boron tolerance and transport in microbial systems.

Solid-phase extraction of Mn(II) and slurry analysis of the sorbent by electrothermal atomic absorption spectrometry.

In this study, a challenging preconcentration/separation method based on the sorption of manganese on ethylene glycol dimethacrylatemethacrylic acid copolymer (EGDMA-MA) treated with ammonium pyrrolidine dithiocarbamate (APDC) and its slurry analysis by electrothermal atomic absorption spectrometry was described. Optimum conditions for quantitative sorption, as well as for preparing a homogeneous and stable slurry were investigated. A 100-fold enrichment factor could be reached. The analyte element in certified sea-water and bovine-liver samples were determined in the range of 95% confidence level. The proposed technique is fast, simple, and the risk of contamination is low. The limit of detection of the method for manganese in the slurry of the blank subjected to the proposed procedure was 0.07 microg L(-1) (3delta, N:10) corresponding to 0.56 microg kg(-1) slurry.

Effect of a Single Application of CPP-ACPF Varnish on the Prevention of Erosive Tooth Wear: An AAS, AFM and SMH Study.

PURPOSE: The aim of this study was to investigate the in vitro effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride-containing varnish on prevention enamel erosive tooth wear. MATERIALS AND METHODS: A total of 28 enamel samples were prepared from human molars, divided into four groups: CPP-ACPF varnish, TCP-F varnish, NaF varnish, and deionised water. For the remineralisation process stimulated human pooled saliva was used. After treatment, all enamel samples were exposed to 10 ml of Coca Cola. Ca++ release was determined by atomic absorption spectroscopy (AAS). The surface topography was evaluated by atomic force microscopy (AFM). Surface microhardness of enamel was analysed and SMHR % (surface microhardness reduction ) was calculated. Data were analysed with repeated measures analysis of variance (ANOVA). RESULTS: Deionised water demonstrated a statistically significantly higher Ca+2 release compared to those of groups NaF > fTCP > CPP-ACPF, respectively (p <0.01). All groups measured for root-mean-square-roughness (Rrms) showed a statistically significantly difference of 6 × 6 µm2 and 12 × 12 µm2 enamel area (p <0.05) compared with a negative control group. CPP-ACPF varnish showed rougher surfaces than all remineralisation groups. SMHR % of enamels were as follows: CPP-ACPF < fTCP < NaF < deionised water (p <0.01). CONCLUSION: According to the findings of this study; CPP-ACP containing agents have a statistically statistically significant effect on preventing dental erosion. Among these, CPP-ACPF-containing remineralisation agents have the most effect on the remineralisation process.

Slurry analysis after lead collection on a sorbent and its determination by electrothermal atomic absorption spectrometry.

In this study, in order to eliminate the drawbacks of elution step and to reach higher enrichment factors, a novel preconcentration/separation technique for the slurry analysis of sorbent loaded with lead prior to its determination by electrothermal atomic absorption spectrometry was described. For this purpose, at first, lead was collected on ethylene glycol dimethacrylate methacrylic acid copolymer (EGDMA-MA) treated with ammonium pyrolidine dithiocarbamate (APDC) by conventional batch technique. After separation of liquid phase, slurry of the sorbent was prepared and directly pipetted into graphite furnace of atomic absorption spectrophotometer. Optimum conditions for quantitative sorption and preparation of the slurry were investigated. A 100-fold enrichment factor could be easily reached. The analyte element in certified sea-water and Bovine-liver samples was determined in the range of 95% confidence level. The proposed technique was fast and simple and the risks of contamination and analyte loss were low. Detection limit (3delta) for Pb was 1.67 microg l(-1).

Assessment of chromium and nickel levels in surface sea waters and sediments from industrial marine area in Tuzla Aydinli Bay, Istanbul Turkey.

The determination and evaluation of nickel and chromium in Tuzla Aydinli Bay is an important subject since it is an industrial marine area for decades and it is crucial to protect aquatic life which are toxic for the aqueous environment. In this study, 32 samples were collected both from near the coastal shipyard activity to far of the activity areas in Tuzla Aydinli Bay, Istanbul (Turkey) according to the standard guidance. Nickel and chromium were determined in the sea water and sediment samples by graphite furnace atomic absorption spectrometry. The contamination factors and geoaccumulation indices with respect to nickel and chromium were calculated and evaluated. Based on the modified ecological risk assessments, variable results were obtained depending on the selection of control (blank) points.

Determination of Lead in Water Samples by GFAAS after Collection on Montmorillonite with Slurry Introduction.

In this study, a highly accurate, fast and practical separation/enrichment technique is described to determine the Pb in tap water samples by graphite furnace atomic absorption spectrometry. For this purpose, at first, Pb was collected on montmorillonite by batch technique, the supernatant was decanted and the solid phase was slurried in a mixture of 0.1% Triton X-114 and 0.1 mol L-1 HNO3 then directly introduced into graphite furnace without elution. Since the elution step was not applied, the method was simpler and faster compared to conventional techniques. The risks of elution step on the precision and recovery were eliminated. Up to 50-fold enrichment could be obtained by this method. The limit of detection (3δ, N = 10) and characteristic concentration of the method for Pb were 0.46 and 1.13 µg L-1, respectively. In addition, the Pb in water samples (tap and river) collected from different regions of Turkey were determined.

A Practical Application of Solid-phase Extraction Using a Syringe Filled with Sorbent for the Determination of Lead and Cadmium in Water.

In this study, at first the synthesis of 3-chloro-2-hydroxypropyl methacrylate-ethylene glycole dimethacrylate co-polymer beads and its modification with tris(2-aminoethyl) amine is described. Characterization of the polymer was done by FTIR and SEM. The functional co-polymer was filled in a disposable pipet tip and tightly connected to a 50-mL syringe for the separation and the enrichment of lead and cadmium prior to their determination by flame atomic absorption spectrometry. The sample and then the eluate were subsequently drawn and discharged to retain and desorb lead and cadmium by means of the syringe, respectively. Both analytes were quantitatively retained at pH 4 and eluted using 3.0 mol L-1 of HNO3 at flow rates of approximately 10 mL min-1. Under the optimum conditions, the enrichment factors of up to 50-fold both elements could be obtained by drawing and discharging 250 mL (5 × 50 mL) of the sample, and then 5 mL of the eluent. The recoveries were >90%. The limits of detection (3σ; N = 10 of blank) for Pb and Cd were 0.0034 and 0.0016 mg L-1 for a 50-fold enrichment, respectively. The analyte concentrations in a certified waste water reference agreed within the certified values in the 95% confidence range.

Solid sampling determination of total fluorine in baby food samples by high-resolution continuum source graphite furnace molecular absorption spectrometry.

This study describes the applicability of solid sampling technique for the determination of fluorine in various baby foods via molecular absorption of calcium monofluoride generated in a graphite furnace of high-resolution continuum source atomic absorption spectrometry. Fluorine was determined at CaF wavelength, 606.440nm in a graphite tube applying a pyrolysis temperature of 1000°C and a molecule forming temperature of 2200°C. The limit of detection and characteristic mass of the method were 0.20ng and 0.17ng of fluorine, respectively. The fluorine concentrations determined in standard reference sample (bush branches and leaves) were in good agreement with the certified values. By applying the optimized parameters, the concentration of fluorine in various baby foods were determined. The fluorine concentrations were ranged from

Determination of Chlorine in Milk via Molecular Absorption of SrCl Using High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry.

Total chlorine in milk was determined via the molecular absorption of diatomic strontium monochloride at 635.862 nm using high-resolution continuum source graphite furnace atomic absorption spectrometry. The effects of coating the graphite furnace, using different modifiers, amount of molecule-forming element, and different calibrants were investigated and optimized. Chlorine concentrations in milk samples were determined in a Zr-coated graphite furnace using 25 µg of Sr as the molecule-forming reagent and applying a pyrolysis temperature of 600 °C and a molecule-forming temperature of 2300 °C. Linearity was maintained up to 500 µg mL(-1) of Cl. The method was tested by analyzing a certified reference wastewater. The results were in the uncertainty limits of the certified value. The limit of detection of the method was 1.76 µg mL(-1). The chlorine concentrations in various cow milk samples taken from the market were found in the range of 588-1472 mg L(-1).

Determination of total sulfur concentrations in different types of vinegars using high resolution flame molecular absorption spectrometry.

Total sulfur concentrations in vinegars were determined using molecular absorption of carbon monosulfide (CS) determined with a high-resolution continuum source flame atomic absorption spectrometer. The molecular absorption of CS was measured at 258.056nm in an air-acetylene flame. Due to non-spectral interference, as well as the different sensitivities to some sulfur compounds, all sulfur species were oxidized to sulfate using a HNO3 and H2O2 mixture and the analyte addition technique was applied for quantification. The limit of detection (LOD) and limit of quantification (LOQ) were 11.6 and 38.6mgL(-1), respectively. The concentrations of sulfur in various vinegars ranged from ⩽LOD to 163.6mgL(-1).

Microwave plasma atomic emission spectrometric determination of Ca, K and Mg in various cheese varieties.

Microwave plasma-atomic emission spectrometry (MP-AES) was used to determine calcium, magnesium and potassium in various Turkish cheese samples. Cheese samples were dried at 100 °C for 2 days and then digested in a mixture of nitric acid/hydrogen peroxide (3:1). Good linearities (R(2) > 0.999) were obtained up to 10 µg mL(-1) of Ca, Mg and K at 445.478 nm, 285.213 nm and 766.491 nm, respectively. The analytes in a certified reference milk powder sample were determined within the uncertainty limits. Moreover, the analytes added to the cheese samples were recovered quantitatively (>90%). All determinations were performed using aqueous standards for calibration. The LOD values for Ca, Mg and K were 0.036 µg mL(-1), 0.012 µg mL(-1) and 0.190 µg mL(-1), respectively. Concentrations of Ca, K and Mg in various types of cheese samples produced in different regions of Turkey were found between 1.03-3.70, 0.242-0.784 and 0.081-0.303 g kg(-1), respectively.

Method development for the determination of calcium, copper, magnesium, manganese, iron, potassium, phosphorus and zinc in different types of breads by microwave induced plasma-atomic emission spectrometry.

A novel method was developed for the determination of calcium, magnesium, potassium, iron, copper, zinc, and manganese and phosphorous in various kinds of breads samples sold in Turkey by microwave plasma-atomic emission spectrometry (MIP-AES). Breads were dried at 100 °C for one day, ground thoroughly and then digested using nitric acid/hydrogen per oxide (3:1). The analytes in certified reference wheat flour and maize flour samples were determined in the uncertainty limits of the certified values as well as the analytes added to the mixture of ground bread and acid mixture prior to digestion were recovered quantitatively (>90%). Therefore, all determinations were made by linear calibration technique using aqueous standards. The LOD values for Ca, Cu, Fe, K, Mg, Mn, P and Zn were 13.1, 0.28, 4.47, 118, 1.10, 0.41, 7550 and 3.00 ng mL(-1), respectively. No spectral interference was detected at the working wavelengths of the analytes.

Determination of sulphur in various vegetables by solid sampling high-resolution electrothermal molecular absorption spectrometry.

Sulphur was determined in various vegetables via molecular absorption of carbon monosulphide (CS) at 258.056 nm using a solid sampling high resolution continuum source electrothermal atomic absorption spectrometer (SS HR-CS ETAAS). Samples were dried, ground and directly introduced into the ruthenium coated graphite furnace as 0.05 to 0.50mg. All determinations were performed using palladium+citric acid modifier and applying a pyrolysis temperature of 1000 °C and a volatilisation temperature of 2400 °C. The results were in good agreement with certified sulphur concentrations of various vegetal CRM samples applying linear calibration technique prepared from thioacetamide. The limit of detection and characteristic mass of the method were 7.5 and 8.7 ng of S, respectively. The concentrations of S in various spinach, leek, lettuce, radish, Brussels sprouts, zucchini and chard samples were determined. It was showed that distribution of sulphur in CRM and grinded food samples were homogeneous even in micro-scale.

Molecule formation mechanisms of strontium mono fluoride in high-resolution continuum source electrothermal atomic absorption spectrometry.

In this study, the molecule formation mechanisms of strontium mono fluoride used for the determination of fluorine in a high-resolution continuum source atomic absorption spectrophotometer was investigated. To distinguish between the gas-phase and the condensed-phase mechanisms, the analyte (F) and the molecule forming element (Sr) were injected on the solid sampling platform manually, as mixed or separately, and the absorbances/peak shapes were compared. There was no significant difference between the absorbances. In addition, the peak shapes and the appearance times were almost the same for the two cases. It was proposed that the main pathway for SrF formation is a gas-phase combination reaction between Sr and F. When Sr and F were mixed on the platform, it was expected that at first SrF2 would be formed in the condensed phase, and then at elevated temperatures it was partly decomposed while either losing one F atom to form SrF, or completely decomposed to its atoms in the gas phase.

Determination of fluorine in milk samples via calcium-monofluoride by electrothermal molecular absorption spectrometry.

The determination of fluorine in milk samples via the molecular absorption of calcium mono-fluoride (CaF) was performed using a HR-CS-ETAAS. For this purpose, calcium was pipetted to graphite furnace together with samples. The amount of Ca and the graphite furnace program were optimised. Fluorine was determined in pyrolytically coated platforms at 606.440 nm applying a pyrolysis temperature of 700 °C and a molecule forming temperature of 2250 °C. Finally, applying standard addition technique, F contents of several milk samples were determined. The results obtained by linear calibration and standard addition techniques were significantly different which can be attributed to non-spectral interferences in milk due to matrix concomitants. Therefore, in order to tolerate the errors, the F contents of several milk samples were determined applying standard addition technique. However, since the ingredients of milk samples change for different kinds, the F in each sample was determined from its own standard addition curve. The range of F content for the milk samples were 0.027-0.543 µg mL(-1). The limit of detection and characteristic mass of the method were 0.26 and 0.13 ng of F, respectively.

Determination of total sulfur in food samples by solid sampling high-resolution continuum source graphite furnace molecular absorption spectrometry.

The determination of sulfur in food samples via the rotational molecular absorption of carbon monosulfide (CS) was performed using a solid sampling high-resolution continuum source electrothermal atomic absorption spectrophotometer (SS-HR-CS-ETAAS). In the presence of plenty of carbon in the graphite furnace as well as in food samples, CS was formed in the gas phase without the addition of any molecule forming element externally. The effects of the wavelength selected to detect CS, graphite furnace program, amount of sample, coating of the graphite tube and platform with Ir, and the use of a Pd modifier on the accuracy, precision, and sensitivity were investigated and optimized. Sulfur was determined in an iridium-coated graphite tube/platform at 258.056 nm by applying a pyrolysis temperature of 1000 °C and a molecule forming temperature of 2400 °C. The calibration curve prepared from Na2S was linear between 0.01 µg (LOQ) and 10 µg of S. The accuracy of the method was tested by analyzing certified reference spinach and milk powder samples by applying a linear calibration technique prepared from aqueous standard. The results were in good agreement with certified values. The limit of detection and characteristic mass of the method were 3.5 and 8.1 ng of S, respectively. By applying the optimized parameters, the concentrations of S in onion and garlic samples were determined.