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A set of homozygous diploid deletion mutants of the yeast Saccharomyces cerevisiae was screened for the genes required for tolerance to aliphatic alcohols. The screen identified 137, 122 and 48 deletion mutants sensitive to ethanol, 1-propanol and 1-pentanol, respectively. A number of the genes required for ethanol tolerance were those also required for tolerance to other alcohols. Numerous mutants with defective genes encoding for vacuolar H+ -ATPase (V-ATPase) were cosensitive to these alcohols. A global screening approach of yeast deletion library mutants was useful in elucidating the mechanisms of alcohol tolerance based on different lipophilicities.

Plant-derived essential oils with monoterpenoids have been used as antifungal drugs since ancient times, but the mode of action of these natural hydrocarbons at the molecular level is not understood. In order to understand the mechanisms of toxicity of alpha-terpinene (a cyclic monoterpene), a culture of Saccharomyces cerevisiae was exposed to 0.02% alpha-terpinene for 2 h and transcript profiles were obtained using yeast DNA arrays. These profiles, when compared with transcript profiles of untreated cultures, revealed that the expression of 793 genes was affected. For 435 genes, mRNA levels in treated cells compared with control cells differed by more than two-fold, whereas for 358 genes, it was0.5-fold. Northern blots were performed for selected genes to verify the microarray results. Functional analysis of the up-regulated genes indicates that, similar to commonly used antifungal drugs, alpha-terpinene exposure affected genes involved in ergosterol biosynthesis and sterol uptake. In addition, transcriptional induction of genes related to lipid metabolism, cell wall structure and function, detoxification and cellular transport was observed in response to terpinene toxicity. Notably, the functions of 192 up-regulated genes are still unknown, but their characterization will probably shed light on the mechanisms of drug resistance and sensitivity. Taken together, this study showed that alpha-terpinene has strong antifungal activities and its modes of action resemble those of presently used antifungal drugs.

Capsaicin is a pungent element in a variety of red peppers that are widely used as food additives and considered to be an antimicrobial factor. For our tests, we used yeast DNA micro-array methods to understand the mechanisms of inhibitory effects of capsaicin. The capsaicin treatment significantly induced 39 genes from approximately 6,000 genes. These induced genes were classified as multi-drug resistance transporter genes, membrane biosynthesis genes, genes encoding stress proteins, and uncharacterized genes. The growth abilities of the strains with the deletion of the induced genes suggest that capsaicin is pumped out of the yeast cells by the PDR5 transporter.

A barotolerant mutant of Saccharomyces cerevisiae and its parent were compared with respect to the barotolerance of each strain, intracellular content of trehalose, amounts of three major heat shock proteins (hsps), relative proportion of unsaturated and saturated fatty acids in membrane phospholipids, and membrane fluidity. Changes in the amount of trehalose, but not hsps, were associated with changes in the barotolerance of each strain during the different phases of growth and with the difference in barotolerance between the mutant and parent strain. The membrane fluidity in the case of the mutant was low, while that of the parent was high. These results suggest that accumulation of trehalose and the condition of the membrane are more important for barotolerance than accumulation of hsps.

A comparison of barotolerance, thermotolerance and oxygen tolerance was made under different physiological conditions, such as heat shocked and recovered state, different growth phases and changes of physiological conditions by mutations. The three kinds of tolerance showed similar features under different physiological conditions. We suggest that the damage caused by hydrostatic pressure may be essentially the same as that due to high temperature and oxidative stress in yeast.

In Saccharomyces cerevisiae, heat shock treatment provides protection against subsequent hydrostatic pressure damage. Such an induced hydrostatic pressure resistance (barotolerance) closely resembles the thermotolerance similarly induced by heat shock treatment. The parallel induction of barotolerance and thermotolerance by heat shock suggests that hydrostatic pressure and high temperature effects in yeast may be tightly linked physiologically.

Thirteen new types of oxygen-sensitive mutants were isolated from Azotobacter vinelandii, without any selection on carbon sources. Three of these showed decreased respiratory or catalase activity, and the other ten, the same level of activity as the parent strain. The oxygen protection mechanism appears due not only to the respiratory activity but may also involve catalase or another, yet unknown, factor(s).

Association of cellular influences and physical and chemical properties were examined for 24 kinds of industrial metal oxide nanoparticles: ZnO, CuO, NiO, Sb(2)O(3), CoO, MoO(3), Y(2)O(3), MgO, Gd(2)O(3), SnO(2), WO(3), ZrO(2), Fe(2)O(3), TiO(2), CeO(2), Al(2)O(3), Bi(2)O(3), La(2)O(3), ITO, and cobalt blue pigments. We prepared a stable medium dispersion for each nanoparticle and examined the influence on cell viability and oxidative stress together with physical and chemical characterizations. ZnO, CuO, NiO, MgO, and WO(3) showed a large amount of metal ion release in the culture medium. The cellular influences of these soluble nanoparticles were larger than insoluble nanoparticles. TiO(2), SnO(2), and CeO(2) nanoparticles showed strong protein adsorption ability; however, cellular influences of these nanoparticles were small. The primary particle size and the specific surface area seemed unrelated to cellular influences. Cellular influences of metal oxide nanoparticles depended on the kind and concentrations of released metals in the solution. For insoluble nanoparticles, the adsorption property was involved in cellular influences. The primary particle size and specific surface area of metal oxide nanoparticles did not affect directly cellular influences. In conclusion the most important cytotoxic factor of metal oxide nanoparticles was metal ion release.

Platinum nanoparticles have industrial application, for example in catalysis, and are used in consumer products such as cosmetics and supplements. Therefore, among the many nanoparticles, platinum is one of the more accessible nanoparticles for consumers. Most platinum nanoparticles that are used in cosmetics and supplements which have an anti-oxidant activity are modified particles. However, the cellular influences of pristine platinum nanoparticles are still unclear, although it has been reported that platinum nanoparticles induce oxidative stress. In this study, we investigated the cellular influences induced by pure pristine platinum nanoparticles. Platinum nanoparticles of 100% purity were dispersed in a cell culture medium and stable medium dispersion was obtained. The platinum nanoparticle medium dispersion was applied to two kinds of cultured cells, A549 and HaCaT cells, and the cellular influences were examined. Cell viability (MTT assay), cell proliferation (clonogenic assay), apoptosis induction (caspase-3 activity), intracellular ROS level (DCFH assay), and lipid peroxidation level (DPPP assay) were measured as markers of cellular influences. Transmission electron microscope observation showed cellular uptake of platinum nanoparticles. However, the platinum nanoparticles did not drive any markers. It is known that some metal oxide nanoparticles such as NiO and CuO show severe cytotoxicity via metal ion release. Compared with these toxic nanoparticles, the platinum nanoparticles used in this study did not release platinum ions into the culture media. These results suggest that the physically and chemically inactive cellular influences of platinum nanoparticles are small.

The existence of a carrier-bound pathway for inorganic sulfate assimilation has been proposed in Chlorella and Escherichia coli. The possibility that the sulfonyl group of active sulfate is transferred to a specific organic acceptor to form thiosulfate ester was examined with Salmonella typhimurium LT-2. Some 11% of the radioactive products from [35S]-3′-phosphoadenosine 5′-phosphosulfate were transferred to high molecular weight compounds, and the remainder of the product is identified as free inorganic sulfite. Apparent thiosulfonate reductase activity was detected in the reaction mixtures containing S-sulfoglutathione and NADPH as conceivable substrates, but not with partially purified sulfite reductase. The former activity was attributable to the nonenzymatic reaction, sulfitolysis. Through these in vitro experiments the existence of the carrier-bound pathway was disproved.

The metabolism of S-sulfocysteine was studied in Salmonella typhimurium. Nutritional experiments with sulfite- and sulfide-requiring mutants ascertained that this amino acid is converted into cysteine and sulfite, and served exclusively as a sulfur source. Two different NADPH- depending systems able to participate in the metabolism of S-sulfocysteine were detected in a crude extract. Both systems were purified and identified as glutathione-glutathione reductase and thioredosin-thioredoxin reductase. The latter system seems to function more efficiently.