Saccharomyces Cerevisiae Extract Research Articles

Effects of dietary fermented Saccharomyces cerevisiae extract (Hilyses) supplementation on growth, hematology, immunity, antioxidants, and intestinal health in Nile tilapia

This study investigated the effects of dietary supplementation with the product Hilyses on growth performance, feed utilization, nutrient composition, hematological parameters, serum biochemistry, immune function, antioxidant status, and digestive enzyme activity in juvenile Nile tilapia (Oreochromis niloticus, initial body weight 4.24 ± 0.01 g). The fish were fed diets supplemented with Hilyses at concentrations of 0, 1, 2, or 3 g/kg for a period of 8 weeks. The results showed that supplementation with Hilyses at levels up to 2 g/kg diet significantly improved final body weight, weight gain, specific growth rate, feed efficiency ratio, protein efficiency ratio, apparent protein utilization, and energy utilization compared to the control diet without Hilyses. Carcass crude protein content and moisture were significantly higher in Hilyses-fed groups, while crude lipid content decreased at the 3 g/kg supplementation level. Hilyses supplementation enhanced various hematological parameters, including increased red blood cell count, total leukocyte count, hemoglobin concentration, hematocrit, and mean corpuscular volume. Serum biochemistry and immune function markers like total protein, albumin, complement component C3, IgM, and IgG were significantly elevated in the 2 and 3 g/kg Hilyses groups. Antioxidant enzyme activities (catalase, glutathione peroxidase, total superoxide dismutase) were enhanced, and lipid peroxidation was reduced, in the 2 g/kg Hilyses group. Digestive enzyme activities, particularly protease and lipase, were also improved with Hilyses supplementation. Histological examination showed reduced lipid deposition in the liver and increased branching of intestinal villi at the 2 g/kg Hilyses level. Overall, these results indicated that dietary Hilyses supplementation at 2 g/kg diet optimizes growth, feed utilization, nutrient composition, hematology, immunity, antioxidant status, and digestive function in juvenile Nile tilapia.

How does a Saccharomyces cerevisiae extract influence the components of isolated rotavirus particles from stool samples collected in a clinical setting from children?

Human Rotavirus (HRV) is the causative pathogen of severe acute enteric infections that cause mortality among children worldwide. This study focuses on developing a new and effective treatment for rotavirus infection using an extract from Saccharomyces cerevisiae, aiming to make this treatment easily accessible to everyone. 15 antigens and 26 antibodies were detected in serum and stool using ELISA. The titers of HRVq1, HRVq2, HRVC1, and HRVC2 on Vero cells were determined to be 1.2x106, 3.0x106, 4.2x106, and 7.5x105 (Plaque forming unit, PFU/ml) four days after infection, respectively. The HRVq1 isolate induced cytopathic effects, i.e., forming multinucleated, rounded, enlarged, and expanding gigantic cells. RT-PCR identified this isolate, and the accession number 2691714 was assigned to GeneBank. The molecular docking analysis revealed that nonstructural proteins (NSPs) NSP1, NSP2, NSP3, NSP4, NSP5, and NSP6 exhibited significant binding with RNA. NSP2 demonstrated the highest binding affinity and the lowest binding energy (−8.9 kcal/mol). This affinity was maintained via hydrophobic interactions and hydrogen bonds spanning in length from 1.12 Å to 3.11 Å. The ADMET and bioactivity predictions indicated that the yeast extract possessed ideal solubility, was nontoxic, and did not cause cancer. The inhibitory constant values predicted for the S. cerevisiae extract in the presence of HRV vital proteins varied from 5.32 to 7.45 mM, indicating its potential as a viable drug candidate. Saccharomyces cerevisiae extract could be utilized as a dietary supplement to combat HRV as an alternative dietary supplement.

Protective effect of Saccharomyces cerevisiae in Rattus norvegicus Ischemic Stroke Model

Stroke is one of the leading causes of morbidity and mortality in all ages. Ischemic stroke activates excitotoxic glutamate cascade leading to brain tissue injury. Saccharomyces cerevisiae is a unicellular yeast widely found in nature. S. cerevisiae is neuroprotective and able to increase the differentiation of hematopoietic stem cells (HSCs) into neuronal cells. it may increase levels of neuroprotectant BDNF in the brain tissue, therefore increase the protection of neurons. BDNF may prevent glutamate-driven excitotoxicity by reducing glutamate levels. This study uses a randomized post-test only controlled group design. In this in vivo study, rodent models of ischemic stroke were divided into five groups comprising of the negative control group, positive control group, intervention group 1 (18mg/kgBW), intervention group 2 (36mg/kgBW) and intervention group 3 (72 mg/kgBW). Groups treated with Saccharomyces cerevisiae extract showed significantly increased BDNF levels in the brain tissue, and the expression of the glutamate level was significantly reduced (P <0.05) compared to the positive control group. Thus Saccharomyces cerevisiae has a promising potential to become a therapy against ischemic stroke disease. however further research is needed regarding the efficacy and toxicity of Saccharomyces cerevisiae.

Inhibitory effect of Saccharomyces cerevisiae extract obtained through ultrasound-assisted extraction on melanoma cells

Although the immune enhancing effect of yeast has been widely reported, studies specifically investigating its effects on skin cancer are lacking. Therefore, this study aimed to develop a yeast extract capable of inhibiting melanoma cells using ultrasound technology, which can lyse the cell walls allowing subsequent rapid yeast extraction. To compare the extraction efficiency across different extraction methods, the total yield, as well as total glucan, α-glucan, and β-glucan yields were measured. Ultrasound-assisted extract of yeast (UAEY) was found to effectively inhibit melanoma cell growth and proliferation as well as the expression of cyclin D1 and c-myc, in vitro. Additionally, the extract reduced melanoma tumor volume and cyclin D1 levels in BALB/c nu/nu mice. The optimal extraction conditions were 0.2 M NaOH, 3 h, 70 °C, 20 kHz, and 800 W, resulting in an increased total extraction and β-glucan yields of 73.6% and 7.1%, respectively, compared with that achieved using a conventional chemical (0.5 M NaOH) extraction method. Taken together, the results of this study suggest that UAEY may represent an effective anti-skin cancer agent.

Saccharomyces cerevisiae extracts improved the effects of a low fishmeal, complex plant protein diet in the orange-spotted grouper, Epinephelus coioides

Six iso-nitrogenous and iso-lipidic experimental diets were formulated to evaluate the effects of Saccharomyces cerevisiae extracts, as part of a low fishmeal diet with a complex plant protein source, on the orange-spotted grouper (Epinephelus coioides). In positive control group, fishmeal was the only protein source (FM). The negative control group (Y0) was fed low amounts of fishmeal, and plant protein was used as the protein source. The other diets were supplemented with Saccharomyces cerevisiae extract: 1 g/kg (Y1), 2 g/kg (Y2), 5 g/kg (Y5), and 10 g/kg (Y10). The Epinephelus coioides were divided into six groups, with three replicates per group and 30 groupers per replicate. The experiment lasted for 56 days. The results showed that there was no significant difference in weight gain rate and specific growth rate of FM, Y0 and Y2 groups (P > 0.05). In foregut, mucosal folds length in Y2 group was significantly greater than that in Y0, Y1 and Y10 groups (P < 0.05). The muscle thicknesses of foregut in Y2 and Y5 groups were significantly higher than those in other groups (P < 0.05). The muscle thicknesses of midgut and hindgut in Y2 group were significantly higher than those in Y0 group (P < 0.05). IL-1β and TNF-α in Y1 group were significantly downregulated compared with Y0 group (P < 0.05). After Vibrio harveyi challenge, survival rate in Y1 and Y10 groups was significantly greater than that in Y0 group (P < 0.05). These results indicated that compared with the negative control group, the addition of 2 g/kg S. cerevisiae extract could increase the mucosal folds length of the foregut, and the muscle thickness of the entire intestine, and maintain the growth similar to that of the positive control group. Adding S. cerevisiae extract to feed may improve the immune capacity of E. coioides, but the improvement was not obvious under the challenge of V. harveyi.

Biosynthesis of palladium nanoparticles using Saccharomyces cerevisiae extract and its photocatalytic degradation behaviour

In this article, we have discussed the biosynthesis of palladium nanoparticles (PdNPs) using aqueous Saccharomyces cerevisiae extract and its photocatalytic application. The biosynthesised PdNPs were characterised by UV-Vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Atomic force microscopy (AFM). The formation of PdNPs was confirmed from the disappearance of the peak at 405 nm in the UV-Vis spectrum. Agglomerated and hexagonal shaped PdNPs were noted by SEM. FTIR was performed to identify the biomolecules responsible for the synthesis of PdNPs. Bioactive compounds in the yeast extract acted as secondary metabolites which facilitated the formation of PdNPs. The yeast synthesised PdNPs degraded 98% of direct blue 71 dye photochemically within 60 min under UV light.

Expanded metabolite coverage of Saccharomyces cerevisiae extract through improved chloroform/methanol extraction and tert-butyldimethylsilyl derivatization

We present an improved extraction and derivatization protocol for GC–MS analysis of amino/non-amino acids in Saccharomyces cerevisiae. Yeast cells were extracted with chloroform: aqueous-methanol (1:1, v/v) and the resulting non-polar and polar extracts combined and dried for derivatization. Polar and non-polar metabolites were derivatized using tert-butyldimethylsilyl (t-BDMS) dissolved in acetonitrile. Using microwave treatment of the samples, the derivatization process could be completed within 2 h (from >20 h of the conventional method), providing fully derivatized metabolites that contain multiple derivatizable organic functional groups. This results in a single derivative from one metabolite, leading to increased accuracy and precision for identification and quantification of the method. Analysis of combined fractions allowed the method to expand the coverage of detected metabolites from polar metabolites i.e. amino acids, organic acids and non-polar metabolites i.e. fatty alcohols and long-chain fatty acids which are normally non detectable. The recoveries of the extraction method was found at 88 ± 4%, RSD, N = 3 using anthranilic acid as an internal standard. The method promises to be a very useful tool in various aspects of biotechnological applications i.e. development of cell factories, metabolomics profiling, metabolite identification, 13C-labeled flux analysis or semi-quantitative analysis of metabolites in yeast samples.

Effects of Saccharomyces cerevisiae supplementation on immune response, hematological parameters, body composition and disease resistance in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792)

Summary Natural substances are now generally preferred over chemical and synthetic compounds for the growth and immune enhancement of aquatic organisms. The aim of this study was to evaluate the effect of Saccharomyces cerevisiae extract and hydrolyzed powder on immunity, hematological parameters and body composition in rainbow trout, Oncorhynchus mykiss. Six hundred rainbow trout (50 ± 5 g mean weight) were acclimated to laboratory conditions and then randomly divided into four groups of triplicate tanks. The first group was fed with a commercial diet (control) without supplementation. The second and third groups were given a diet supplemented with 1% of yeast extract and hydrolyzed powder, respectively. The fourth group was also fed with a basal diet supplemented with 0.5% of both substances. Fish were cultured in 300-L polyethylene tanks for 60 days; immune and hematological parameters, fillet composition and disease resistance were analyzed at days 0, 30 and 60. Results showed that a combination of Saccharomyces cerevisiae extract and hydrolyzed powder could improve the immunity and alter hematological parameters of the rainbow trout compared to the control. Mortality rates of fish fed yeast extract and hydrolyzed powder were also lower than in fish fed the control diet after challenging with Yersinia ruckeri. There were no significant changes in rainbow trout fillet composition compared to the control. It can be concluded that fish diet supplementation with a mixture of yeast extract hydrolyzed powder is preferable compared to each one used alone.

Effects of Saccharomyces cerevisiae extract on haematological parameters, immune function and the antioxidant defence system in breeder hens fed aflatoxin contaminated diets

1. The study was conducted to investigate the efficacy of Saccharomyces cerevisiae extract (SC) on haematological parameters, immune function, and the antioxidant defence system in breeder hens fed a diet contaminated with low level aflatoxin (AF). 2. Forty-eight Ross 308 breeder hens were fed on diets containing AF (0 or 100 µg/kg) and SC (0 or 1 g/kg) in a 2 × 2 factorial arrangement. Red blood cell (RBC), white blood cell (WBC), and platelet counts, differential leucocyte counts, blood CD3+, CD4+, CD8+ and CD5+ T cell ratios, phagocytic activity and oxidative burst of heterophils, plasma and liver catalase activity, and malondialdehyde (MDA) and ascorbic acid concentrations were measured. 3. Plasma and liver MDA concentrations increased (P < 0·05), liver catalase activity decreased (P < 0·05) and total WBC count tended to decrease (P = 0·082) in hens fed the contaminated diet. WBC count, monocyte percentage, phagocytic activity and oxidative burst of heterophils increased (P < 0·05), and plasma MDA concentration tended to decrease (P = 0.088) in SC extract supplemented hens. There was a significant interaction between AF and SC on heterophil, lymphocyte, CD5+ cell percentages, and plasma catalase activity. Blood heterophil percentage decreased but lymphocyte percentage increased in hens fed on the AF contaminated diet without SC supplementation. SC supplementation counteracted the negative effect of AF on heterophils and lymphocytes. The CD5+ cell percentage decreased in unsupplemented hens fed the AF contaminated diet and this negative effect was minimised in SC supplemented hens. Plasma catalase activity increased in SC supplemented hens fed the uncontaminated diet whereas the effect of SC decreased in hens fed the AF contaminated diet. 4. The SC reduced some of the some adverse effects of AF, and improved functions of the non-specific immune system. Therefore, the SC extract which has been used for improving productive performance in birds and mammals may also be useful for modulating some of the effects of a low level, chronic dosage of AF.

The effects of Saccharomyces cerevisiae extract on the weight of some organs, liver, and pancreatic digestive enzyme activity in breeder hens fed diets contaminated with aflatoxins

The effects of the Saccharomyces cerevisiae extract on some organ, liver, and pancreatic digestive enzymes in breeder hens fed on aflatoxin (AF)-contaminated feed were investigated. Forty-eight 58-wk-old Ross 308 breeder hens were used. The hens were fed diets containing 0 or 100 µg of AF/kg and 0 or 1 g of S. cerevisiae/kg in a 2×2 factorial arrangement of treatments. Although serum alkaline phosphatase levels were significantly higher, serum alkaline aminotransferase (P=0.068) and gamma-glutamyltransferase (P=0.067) levels tended to increase (P<0.05) in hens fed the AF-contaminated diet than those of hens fed the uncontaminated diet. Both AF and S. cerevisiae extract increased (P<0.001) pancreatic amylase activity, but the effect was not additive, resulting in an AF×S. cerevisiae extract interaction (P<0.001). α-Amylase activity in duodenum was lower (P<0.001) in hens fed the AF-contaminated diet. Duodenum α-amylase activity was higher (P=0.024), but jejunum α-amylase activity was lower in S. cerevisiae extract-supplemented hens than that of nonsupplemented hens. There was a significant interaction between AF and S. cerevisiae extract on pancreatic and duodenal lipase activity. Pancreatic lipase activity decreased in hens fed the AF-contaminated diet. However, S. cerevisiae supplementation extract minimized this effect of AF on pancreatic lipase activity. Duodenal lipase activity was decreased in hens fed the AF-contaminated diet without S. cerevisiae extract supplementation. However, there were not any significant differences between hens fed the AF-contaminated diet and hens fed the uncontaminated diet after S. cerevisiae extract supplementation. Pancreatic trypsin activity was higher (P=0.044) in hens fed the AF-contaminated diet than that of hens fed the uncontaminated diet. There was a significant interaction between AF and S. cerevisiae extract on pancreatic chymotrypsin activity. It was increased in hens fed the AF-contaminated diet without S. cerevisiae extract supplementation. However, S. cerevisiae extract supplementation counteracted this negative effect of AF on pancreatic chymotrypsin activity. The treatments did not result in any change in duodenal chymotrypsin activity, but S. cerevisiae supplementation decreased (P<0.05) jejunal chymotrypsin activity. In conclusion, our results showed that addition of 1 g/kg of S. cerevisiae extract reduces the toxic effects of AF on pancreatic lipase and chymotrypsin activity. Therefore, it may be useful to supplement feedstuff with S. cerevisiae extract to reduce the effects of AF in laying breeder hens.

Effect of acibenzolar-S-methyl andSaccharomyces cerevisiaeon the activation ofEucalyptusdefences against rust

Tree defence mechanisms against the fungus Puccinia psidii were examined by comparing the activities of defence-related enzymes (chitinase, peroxidase and phenylalanine ammonia-lyase) of two Eucalyptus grandis × E. urophylla (urograndis) hybrids, previously classified as either susceptible to rust (VR hybrid) or moderately resistant to rust (C0 hybrid). Furthermore, the potential of disease control by artificial activation of host defences using either acibenzolar-S-methyl (ASM) or Saccharomyces cerevisiae extract was also investigated. Greenhouse inoculation trials revealed that the C0 hybrid had lower disease severity than the VR hybrid but following foliar applications of either ASM or S. cerevisiae extract treatment, disease severity (evaluated at 15 days after inoculation) was reduced in both hybrids. This enhanced resistance was associated with the induction of a hypersensitive reaction which appeared to be effective in controlling rust in both clones. The activity of all enzymes differed between clones and inducer treatment. The role of the defence-related enzymes in imparting resistance to eucalypt hybrids against rust is discussed.

Evaluation of dermatological effects of cosmetic formulations containing Saccharomyces cerevisiae extract and vitamins

Saccharomyces cerevisiae extract (SCE) is used in cosmetics since it can act in oxidative stress and improve skin conditions. This study investigated dermatological effects of cosmetic formulations containing SCE and/or vitamins A, C and E. The formulation studied was supplemented or not (F1: vehicle) with vitamins A, C and E esters (F2) or with SCE (F3) or with the combination of vitamins and SCE (F4). Formulations were patch tested on back skin of volunteers. For efficacy studies, formulations were applied on volunteers and transepidermal water loss (TEWL), skin moisture (SM), skin microrelief (SMR) and free radicals protection were analysed after 3 h, 15 and 30 days of application. Volunteers were also asked about efficacy perception. It was observed that F4 provoked a slight erythema in one volunteer. All formulations enhanced forearm SM. Only F3 and F4 presented long term effects on SMR and showed higher texture values; F3 had the highest brightness values. Our results suggest that vitamins and SCE showed effects in SM and SMR. Only formulations containing SC had long term effects in the improvement of SMR. Thus, these kinds of evaluations are very important in cosmetics development to evaluate the best risk and benefit correlation.

Effects of yeast (Saccharomyces cerevisiae) cell components on growth performance, meat quality, and ileal mucosa development of broiler chicks

An experiment was conducted with 240, 1-d-old, male broilers to investigate the effects of Saccharomyces cerevisiae (SC) cell components on the growth performance, meat quality, and ileal mucosa development. There were 4 dietary treatments, each consisting of 6 replicates. Whole yeast (WY), SC extract (YE), and SC cell wall (CW) were added at 0.5, 0.3, and 0.3%, respectively, to the control starter and finisher diets. From 0 to 3 wk of age, a lower feed/gain ratio (P ≤ 0.05) was observed with CW, whereas the WY-fed birds at 4 to 5 wk of age showed a lower feed/gain ratio compared with the control. From 0 to 5 wk of age, WY and CW gave higher BW gains than did the control. The shear force of raw drumstick decreased in the WY treatment relative to the control, and YE and CW treatments were intermediate. The shear forces in cooked breast and drumstick in treatments WY and YE decreased when compared with the control. The amount of 2-thiobarbituric acid-reactive substances (TBARS) in the breast meats of WY, YE, and CW were lower than the control at 10 d of incubation. In raw drumstick meats, TBARS values were lower in treatments WY and YE than that of the control at 6 and 10 d of incubation. At 10 d of incubation, skins from YE and CW treatments had lower TBARS values than did the control. Villus height was greater in WY and CW compared with those in control and YE. No differences were found in crypt depth among the 4 treatments. The villus height/ crypt depth ratios in WY and CW were greater than those of the control and YE. It could be concluded that dietary yeast components, such as WY or CW supplementation improved growth performance. Meat tenderness could be improved by the WY or YE. Both YE and CW had oxidation-reducing effects. Yeast cell wall may improve ileal villus development.

Cell Cycle Regulation of a Novel DNA Binding Complex in Saccharomyces cerevisiae with E2F-like Properties

Using a biochemical approach, we have detected an activity in Saccharomyces cerevisiae extract that displays the same DNA binding specificity as the mammalian E2F transcription factor and interacts with TTTCGCGC promoter elements. Additional studies revealed that this factor, termed SCELA (S. cerevisiae E2F-like activity), also binds to the closely related SCB promoter sequences. SCB sites (consensus: TTTCGTG) are involved in the cell cycle regulation of several S. cerevisiae cyclin genes and have been shown to interact with the heterodimeric yeast Swi4-Swi6 complex. However, genetic studies clearly demonstrate that SCELA is not related to Swi4 or Swi6. These experiments imply that SCB sites are able to interact with at least two activities: Swi4-Swi6 and SCELA. Because SCB sites are critical for the periodic activation of cell cycle genes, we asked whether SCELA is regulated during yeast cell cycle. Employing a temperature-sensitive strain, we were able to demonstrate that the DNA binding activity of SCELA oscillates during the cell cycle and reaches its maximum at the transition between the G1 and S phases. Preliminary studies suggest that this fluctuation is mediated by phosphorylation/dephosphorylation events. Further characterization of SCELA by UV cross-linking experiments indicate a molecular mass of 47 kDa for this activity. In addition, we present evidence strongly suggesting that SCELA is actually the DNA binding moiety of a large 300-kDa protein complex. Together, these studies firmly indicate that SCELA (as part of a larger complex) plays a critical role in cell cycle regulation of SCB-containing genes, such as CLN cyclins and HO endonuclease. This hypothesis is consistent with other studies that conclude that the SCB-mediated cell cycle oscillation of CLN cyclins and HO requires activities that are distinct from Swi4-Swi6. Finally, it is worth mentioning that the similarities between SCELA and E2F, which is a crucial component in mammalian cell cycle regulation, extend well beyond the DNA binding specificity. In analogy to E2F, SCELA oscillates during the cell cycle, interacts with other cellular activities, and binds to promoter elements that are known mediators of cell cycle control. We will discuss possible functions for SCELA in yeast cell cycle regulation and its relationship to E2F.

Molecular tools for inactivating a yeast enzyme in vivo.

As part of an effort to develop a new means of inducibly inactivating cellular proteins in vivo, three monoclonal antibodies which neutralize yeast alcohol dehydrogenase (ADH) activity were isolated and characterized with respect to criteria important for the inactivation strategy. The significance of these criteria is considered, and a general means of generating appropriate antibodies is suggested. All three antibodies described here were specific for ADH I; they did not recognize the closely related isozyme ADH II in a plate-binding assay and did not immunoprecipitate molecules other than ADH from a Saccharomyces cerevisiae extract. Neutralization occurred in a yeast extract and, for two antibodies, was blocked by high concentrations of the coenzyme NAD+. This finding suggests that the antibodies may block enzyme activity by stabilizing an inactive form of ADH lacking bound NAD+. These results provide a foundation for the use of these antibodies to inactivate ADH in vivo.

Molecular tools for inactivating a yeast enzyme in vivo.

As part of an effort to develop a new means of inducibly inactivating cellular proteins in vivo, three monoclonal antibodies which neutralize yeast alcohol dehydrogenase (ADH) activity were isolated and characterized with respect to criteria important for the inactivation strategy. The significance of these criteria is considered, and a general means of generating appropriate antibodies is suggested. All three antibodies described here were specific for ADH I; they did not recognize the closely related isozyme ADH II in a plate-binding assay and did not immunoprecipitate molecules other than ADH from a Saccharomyces cerevisiae extract. Neutralization occurred in a yeast extract and, for two antibodies, was blocked by high concentrations of the coenzyme NAD+. This finding suggests that the antibodies may block enzyme activity by stabilizing an inactive form of ADH lacking bound NAD+. These results provide a foundation for the use of these antibodies to inactivate ADH in vivo.

Structure-activity relationships of sparsomycin: modification at the hydroxyl group

Ten analogues of the antibiotic sparsomycin were prepared and evaluated in several in vitro tests. Nine of them carry a modification at the hydroxymethylene group of the molecules, two have a disulfide bond instead of the S(O)-CH 2-S moiety at the sulfur-containing side chain of the molecules. While the presence of the S-S group decreases the activity of the analogues in all the tests performed, the modification at the OH group has no deleterious effects on the activity when a polyphenylalanine synthesis assay is used in an Escherichia coli extract. The same modifications, however, diminish drastically the activity of the analogues when tested in a similar Saccharomyces cerevisiae extract. A polymerization system in the archaebacterium Halobacterium halobium extract behaves like the eukaryotic preparations. A discrepancy is also found between the results of the polymerization tests and those of the ‘puromycin reaction’ which is also less sensitive to the modified sparsomycin analogues. The results of cell growth inhibition tests in bacteria as well as in eukaryotic organisms agree only partially with the in vitro data.

Mutations preventing expression of sup3 tRNASer nonsense suppressors of Schizosaccharomyces pombe.

Suppression of nonsense codons in Schizosaccharomyces pombe by sup3-e tRNASerUGA or sup3-i tRNASerUAA is reduced or abolished by mutations within the suppressor locus. Twenty-five suppressor-inactive sup3-e genes and thirteen mutant sup3-i genes were isolated from S. pombe genomic clone banks by colony hybridization. Sequence analysis of these revertant alleles corroborates genetic evidence for mutational hotspots within the sup3 tRNA gene. Fifteen types of point mutations or insertions were found. Many of these replace bases which are highly or completely conserved in eucaryotic tRNA genes. Transcription of the altered sup3 genes in a Saccharomyces cerevisiae extract enabled the identification of mutations which affect the rate of 5'-end maturation or splicing of the tRNA precursors or both. A total of seven mutations were found which alter transcriptional efficiencies. Of these, five are located outside the internal transcription control regions.

Mutations preventing expression of sup3 tRNASer nonsense suppressors of Schizosaccharomyces pombe.

Suppression of nonsense codons in Schizosaccharomyces pombe by sup3-e tRNASerUGA or sup3-i tRNASerUAA is reduced or abolished by mutations within the suppressor locus. Twenty-five suppressor-inactive sup3-e genes and thirteen mutant sup3-i genes were isolated from S. pombe genomic clone banks by colony hybridization. Sequence analysis of these revertant alleles corroborates genetic evidence for mutational hotspots within the sup3 tRNA gene. Fifteen types of point mutations or insertions were found. Many of these replace bases which are highly or completely conserved in eucaryotic tRNA genes. Transcription of the altered sup3 genes in a Saccharomyces cerevisiae extract enabled the identification of mutations which affect the rate of 5'-end maturation or splicing of the tRNA precursors or both. A total of seven mutations were found which alter transcriptional efficiencies. Of these, five are located outside the internal transcription control regions.