Growth Of Yeast Cells Research Articles

Stochastic Simulation of Yeast Cells and Its Colony Growth by Using Circular Granular Model for Cases of Growth and Birth Probabilities Depends on Position

Until now, many studies were conducted on microorganisms in order to make the best use of them and prevent the loss. As a type of microorganism that is widely utilized by humans, the yeast has a simple single cell structure that can represent many other complex cell processes and generally has almost elliptical shapes making it easier to model for further investigation. In this study, we model yeast cells with two dimensional circular granular particles and the interaction between them are modeled by the force of gravity, normal force, and Stokes force. The growth and birth factor of yeast cells are modeled stochastic with the simulation is done by using javascript programming language. From the simulation results obtained, showing the growth of yeast cells in the colony has a behavior that is in accordance with the theory, which grows exponentially, as well as the growth of the size of the colony radius whose growth rate is half to the rate of growth of its number of cells.

RESEARCH OF THE EFFICIENCY OF APIP-PRODUCTS APPLICATION IN THE PRACTICE OF PREPARATION OF BIOLOGICAL-ACTIVE, FUNCTIONAL MINORITY PRODUCTS

The demand of consumers for the use of sour milk functional products is analyzed. The recommended sour-milk product was obtained by thermostat from ultra-pasteurized drinking milk with a mass fraction of fat of 3.2%. As a fertiliser was used the preparation «Bifivit» VIVO Kiev Institute of Milk and Meat (Ukraine, Kiev), which includes Bifidobacterium lactis, Bifidobacterium longum, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium infantis, Lactobacillus bulgaricus, Lactobacillus acidophilus, Streptococcusthermophiles. The effectiveness of the use of fermentation of VIVO trade mark – bifiit in the technology of preparation of lactic acid products is proved, which is confirmed by high tartar of lactic acid bacteria in the finished product. The optimum time of digestion of lactic acid is established, which according to the results of studies is 5-6 hours, which corresponds to the optimum acidity of the product – 650T for yoghurts.It is recommended as yogurt fillers to use api products: honey, propolis and pollen, which improve the flavoring properties of the product and enrich them with useful biologically active substances. Beekeeping products are a powerful source of biologically active substances. According to the results of personal studies, the optimum dosages of fillers were determined: floral honey – 6%, propolis – 0.5%, pollen – 5%.The research results show that yeast is present in the yogurt with honey and pollen for the third day. And on the 7th day in the sample with pollen, the amount of yeast exceeded the norm (50 Columns of forming units / ml). Signs of fermentation were observed in this sample. This indicates that when a saw is introduced into the product, a significant amount of foreign microflora enters simultaneously. The most stable microbiological parameters are observed in samples of yogurt with propolis. This may be explained by the fact that propolis is a natural antiseptic, which in some way affects the growth of yeast cells, as well as other microorganisms. Honey has a positive effect on the development of lactic acid microorganisms, but the period of changes in the organoleptic properties of the product with honey is less compared with control samples.

Modulation of ruthenium anticancer drugs analogs with tolfenamic acid: Reactivity, biological interactions and growth inhibition of yeast cell

We synthesized two ruthenium(II) complexes: trans,trans-[Ru(im)2(tfa)2] (1) and trans,trans‑[Ru(in)2(tfa)2] (2) where im = 1H‑imidazole, in = 1H‑indazole and tfa = tolfenamic acid, a potential nonsteroidal anti-inflammatory drug (NSAID). The NSAID was opted as bioactive ligand to understand its synergistic therapeutic effect in structurally analogous Ru(II)-compounds with KP418 (imidazolium trans‑[tetrachloridobis(1H‑imidazole)ruthenate(III)]) and KP1019 (indazolium trans‑[tetrachloridobis(1H‑indazole)ruthenate(III)]). The complexes were studied using various analytical methods and structure was determined by X-ray crystallography. Both the complexes display discrete mononuclear Ru(II) center in {RuN4O2} distorted octahedral geometry. The reactivity of the complexes was tested with potentially important biomolecules involved in metabolism of cancer cells, viz. l‑arginine, dl‑methionine, glutathione and L(+)ascorbate. Such studies intended to provide deeper insights on intracellular speciation and kinetic substitution encountered by Ru-drugs to target alternative cell death pathways. The complexes demonstrate a preferential binding affinity with calf thymus DNA (Kb ~ 104 M−1) and human serum albumin (KHSA = 105 M−1). Both the complexes showed potent inhibition of wild type yeast cell growth in a dose-dependent manner. Yeast cells were used as a powerful model system to study the molecular mechanism of pathobiology which shares a high degree of conservation of both cellular and molecular processes with human cells for assessing toxicity potential of the complexes. Fluorescence imaging studies reveal the localization of both complexes to yeast mitochondria despite its rigid cell wall and induce mitochondrial damage and formation of reactive oxygen species (ROS). The Micrococcal nuclease assay revealed complexes do not alter global nucleosome occupancy and probably target specific regions of the genome.

The influence of low-frequency magnetic field regions on the Saccharomyces cerevisiae respiration and growth

The influence of four low-frequency magnetic field (MF) ranges 10–300 Hz, 10–100 Hz, 10–50 Hz and 50–100 Hz in scanning regime (all frequencies from selected range were scanned during 100 s repetitively during 24 h) on baker’s yeast cells Saccharomyces cerevisiae was examined by continuous measurements of cumulative O2 consumption and cumulative CO2 production over 24 h with Micro-Oxymax® respirometer. Besides respiration activity, measurements of cell growth and glucose uptake were performed as well. Statistical analysis indicated that, among all investigated low-frequency MF ranges, range from 10 Hz to 50 Hz had the greatest influence to yeast cell respiration and cell growth. More precisely, for this region, paired two sample one-tail t-test showed statistically significant differences in cumulative O2 consumption, cumulative CO2 production and S. cerevisiae cell number. Moreover samples exposed to MF range from 10 Hz to 50 Hz showed the same behavior in all five replicates: lower cumulative O2 consumption, higher cumulative CO2 production and higher cell number compared to control sample. This could be important from the application aspect, in industry (food, feed, brewery etc.) and biotechnology, because changes in cells metabolism are not caused by chemical treatment.

Human Aquaporin-5 Facilitates Hydrogen Peroxide Permeation Affecting Adaption to Oxidative Stress and Cancer Cell Migration.

Reactive oxygen species (ROS), including H2O2, contribute to oxidative stress and may cause cancer initiation and progression. However, at low concentrations, H2O2 can regulate signaling pathways modulating cell growth, differentiation, and migration. A few mammalian aquaporins (AQPs) facilitate H2O2 diffusion across membranes and participate in tumorigenesis. AQP3 and AQP5 are strongly expressed in cancer tissues and AQP3-mediated H2O2 transport has been related to breast cancer cell migration, but studies with human AQP5 are lacking. Here, we report that, in addition to its established water permeation capacity, human AQP5 facilitates transmembrane H2O2 diffusion and modulates cell growth of AQP5-transformed yeast cells in response to oxidative stress. Mutagenesis studies revealed that residue His173 located in the selective filter is crucial for AQP5 permeability, and interactions with phosphorylated Ser183 may regulate permeation through pore blockage. Moreover, in human pancreatic cancer cells, the measured AQP5-mediated H2O2 influx rate indicates the presence of a highly efficient peroxiporin activity. Cell migration was similarly suppressed by AQP3 or AQP5 gene silencing and could be recovered by external oxidative stimuli. Altogether, these results unveiled a major role for AQP5 in dynamic fine-tuning of the intracellular H2O2 concentration, and consequently in activating signaling networks related to cell survival and cancer progression, highlighting AQP5 as a promising drug target for cancer therapies.

Cyclin-dependent kinase–mediated phosphorylation of the exocyst subunit Exo84 in late G1 phase suppresses exocytic secretion and cell growth in yeast

In eukaryotic cells, the growth rate is strictly regulated for proper progression of the cell cycle. In the budding yeast Saccharomyces cerevisiae, it was previously shown that cell growth dramatically slows down when the cells start budding at the G1/S transition. However, the molecular mechanism for this G1/S-associated growth arrest is unclear. In this study, using exocytic secretion, cyclin-dependent kinase (CDK) assay, immunoprecipitation, and microscopy, we demonstrate that the exocyst subunit Exo84, which is known to be phosphorylated in mitosis, can also be phosphorylated directly by Cdk1 in the late G1 phase. Of note, we found that the Cdk1-mediated Exo84 phosphorylation impairs exocytic secretion in the late G1 phase. Using conditional cdc mutants and phosphodeficient and phosphomimetic exo84 mutants, we further observed that Cdk1-phosphoryated Exo84 inhibits the exocyst complex assembly, exocytic secretion, and cell growth, which may be important for proper execution of the G1/S-phase transition before commitment to a complete cell cycle. Our results suggest that the direct Cdk1-mediated regulation of the exocyst complex critically contributes to the coordination of cell growth and cell cycle progression.

Characterization of lapachol cytotoxicity: contribution of glutathione depletion for oxidative stress in Saccharomyces cerevisiae.

Over the years, quinones or its derivatives have been extensively studied due to their broad therapeutic spectrum. However, due to the significant structural differences between the individual naturally occurring quinones, investigation of the precise mechanism of their action is essential. In this context, we have analyzed the mechanism of lapachol [4-hydroxy-3-(3-methylbut-2-enyl)naphthalene-1,2-dione] toxicity using Saccharomyces cerevisiae as eukaryotic model organism. Analyzing yeast (wild type, sod1∆, and gsh1∆) cell growth, we observed a strong cytostatic effect caused by lapachol exposure. Moreover, survival of cells was affected by time- and dose-dependent manner. Interestingly, sod1∆ cells were more prone to lapachol toxicity. In this sense, mitochondrial functioning of sod1∆ cells were highly affected by exposure to this quinone. Lapachol also decreased glutathione (GSH) levels in wild type and sod1∆ cells even though glutathione disulfide (GSSG) remained unchanged. We believe that reduction of GSH contents has contributed to the enhancement of lipid peroxidation and intracellular oxidation, effect much more pronounced in sod1∆ cells. Overall, the collected data suggest that although lapachol can act as an oxidant, it seems that the main mechanism of its action initially consists in alkylation of intracellular targets such as GSH and then generating oxidative stress.

Chemogenomic profiling in yeast reveals antifungal mode-of-action of polyene macrolactam auroramycin.

In this study, we report antifungal activity of auroramycin against Candida albicans, Candida tropicalis, and Cryptococcus neoformans. Auroramycin, a potent antimicrobial doubly glycosylated 24-membered polyene macrolactam, was previously isolated and characterized, following CRISPR-Cas9 mediated activation of a silent polyketide synthase biosynthetic gene cluster in Streptomyces rosesporous NRRL 15998. Chemogenomic profiling of auroramycin in yeast has linked its antifungal bioactivity to vacuolar transport and membrane organization. This was verified by disruption of vacuolar structure and membrane integrity of yeast cells with auroramycin treatment. Addition of salt but not sorbitol to the medium rescued the growth of auroramycin-treated yeast cells suggesting that auroramycin causes ionic stress. Furthermore, auroramycin caused hyperpolarization of the yeast plasma membrane and displayed a synergistic interaction with cationic hygromycin. Our data strongly suggest that auroramycin inhibits yeast cells by causing leakage of cations from the cytoplasm. Thus, auroramycin’s mode-of-action is distinct from known antifungal polyenes, reinforcing the importance of natural products in the discovery of new anti-infectives.

Culture of yeast cells immobilized by alginate-chitosan microcapsules in aqueous-organic solvent biphasic system

Immobilization biocatalysis is a potential technology to improve the activity and stability of biocatalysts in nonaqueous systems for efficient industrial production. Alginate-chitosan (AC) microcapsules were prepared as immobilization carriers by emulsification-internal gelation and complexation reaction, and their contribution on facilitating the growth and metabolism of yeast cells were testified successfully in culture medium-solvent biphasic systems. The cell growth in AC microcapsules is superior to that in alginate beads, and the cells in both immobilization carriers maintain much higher activity than free cells, which demonstrates AC microcapsules can confer yeast cells the ability to resist the adverse effect of solvent. Moreover, the performance of AC microcapsules in biphasic systems could be improved by adjusting the formation of outer polyelectrolyte complex (PEC) membrane to promote the cell growth and metabolic ability under the balance of resisting solvent toxicity and permitting substrate diffusion. Therefore, these findings are quite valuable for applying AC microcapsules as novel immobilization carriers to realize the biotransformation of value-added products in aqueous-solvent biphasic systems.

Optimized activated charcoal detoxification of acid-pretreated lignocellulosic substrate and assessment for bioethanol production

This study optimized an activated charcoal (AC) detoxification method for the reduction of three different fermentation inhibitor compounds, while minimising the reducing sugar loss from acid-pretreated sorghum leaf (SL) wastes. Process optimization demonstrated a 98%, 88% and 37% removal efficiency for furfural, 5-hydroxymethylfurfural (HMF) and acetic acid respectively, with a 7% reducing sugar loss. Subsequently, the logistic and modified Gompertz models were used to comparatively evaluate the kinetics of Saccharomyces cerevisiae growth and ethanol production using the non-detoxified (NDF) and optimized detoxified (ODF) substrate. Yeast cell growth and bioethanol kinetic coefficients revealed that the ODF process was more effective than the NDF system. The experimental data generated from this study revealed that a suitable, cost-effective AC detoxification enhanced cell growth and bioethanol production efficiency. These findings pave the way for biomass pretreatment, detoxification and bioethanol process development using lignocellulosic wastes.

A novel functional role of nickel in sperm motility and eukaryotic cell growth

BackgroundMetal ions are essential for numerous life processes. This study aims to investigate the relationship between seminal quality and ion levels in seminal plasma. Basic proceduresA total of 205 semen samples were collected and seminal plasma ion levels were examined with inductively-coupled plasma-mass spectrometry. The nickel function was demonstrated by in vitro assay and cell growth. Main findingsThe low sperm motility group showed distinctively reduced nickel concentration in seminal plasma compared with the normal sperm motility group. However, arsenic, sulfur, selenium, magnesium and zinc were negatively associated with sperm quality. No significant relationship between other examined cations and semen quality was observed. In vitro assay suggested low concentration of nickel significantly increased sperm total motility and progressive motility. Cell growth assay further confirmed nickel promoted eukaryotic yeast cell growth. Nickel level in seminal plasma may play important functions to determine sperm quality. Principal conclusionsOur study reveals a strong correlation between S, Mg, Se, Zn, As, Ni and seminal quality as well as discovers a novel functional role of nickel in sperm motility and eukaryotic cell growth. These findings may provide a potential avenue for assessment of sperm quality and treatment of reproduction disorders.

Yeast Dop1 is required for glycosyltransferase retrieval from the trans-Golgi network

BackgroundGlycosyltransferases are type II membrane proteins that are responsible for glycan modification of proteins and lipids, and localize to distinct cisternae in the Golgi apparatus. During cisternal maturation, retrograde trafficking helps maintain the steady-state localization of these enzymes in the sub-compartments of the Golgi. MethodsTo understand how glycosyltransferases are recycled in the late Golgi complex, we searched for genes that are essential for budding yeast cell growth and that encode proteins localized in endosomes and in the Golgi. We specifically analyzed the roles of Dop1 and its binding partner Neo1 in retaining Golgi-resident glycosyltransferases, in the late Golgi complex. ResultsDop1 primarily localized to younger compartments of the trans-Golgi network (TGN) and seemed to cycle within the TGN. In contrast, Neo1, a P4-ATPase that interacts with Dop1, localized to the TGN. Abolition of DOP1 expression led to defects in the FM4-64 endocytic pathway. Dop1 and Neo1 were required for correct glycosylation of invertase, a secretory protein, at the Golgi. In DOP1-shutdown cells, Och1, a mannosyltransferase that is typically located in the cis-Golgi, mislocalized to the TGN. In addition, the function of multiple glycosyltransferases required for N- and O-glycosylation were impaired in DOP1-shutdown cells. ConclusionsOur results indicate that Dop1 is involved in vesicular transport at the TGN, and is critical for retrieving glycosyltransferases from the TGN to the Golgi in yeast. General significanceGolgi-resident glycosyltransferases recycling from the TGN to the Golgi is dependent on Dop1 and the P4-ATPase Neo1.

Fission yeast cells grow approximately exponentially

ABSTRACTHow the rate of cell growth is influenced by cell size is a fundamental question of cell biology. The simple model that cell growth is proportional to cell size, based on the proposition that larger cells have proportionally greater synthetic capacity than smaller cells, leads to the prediction that the rate of cell growth increases exponentially with cell size. However, other modes of cell growth, including bilinear growth, have been reported. The distinction between exponential and bilinear growth has been explored in particular detail in the fission yeast Schizosaccharomyces pombe. We have revisited the mode of fission yeast cell growth using high-resolution time-lapse microscopy and find, as previously reported, that these two growth models are difficult to distinguish both because of the similarity in shapes between exponential and bilinear curves over the two-fold change in length of a normal cell cycle and because of the substantial biological and experimental noise inherent to these experiments. Therefore, we contrived to have cells grow more than twofold, by holding them in G2 for up to 8 h. Over this extended growth period, in which cells grow up to 5.5-fold, the two growth models diverge to the point that we can confidently exclude bilinear growth as a general model for fission yeast growth. Although the growth we observe is clearly more complicated than predicted by simple exponential growth, we find that exponential growth is a robust approximation of fission yeast growth, both during an unperturbed cell cycle and during extended periods of growth.

Investigating the N‐ and C‐terminal Extensions of the Yeast DEAD‐box Protein Dbp6

DEAD‐box proteins are RNA‐dependent ATPases that are involved in all aspects of RNA metabolism. Also known as DEAD‐box helicases, these enzymes bind RNA and ATP and unwind short RNA duplexes via a highly conserved helicase core. N‐ and C‐terminal extensions that flank this core differ in both length and composition between DEAD‐box proteins and have been shown to contribute to RNA specificity and binding, thereby conferring the diverse cellular roles of DEAD‐box proteins. Here, we are investigating the 192 amino acid N‐terminal and 63 amino acid C‐terminal extensions of Dbp6, a yeast DEAD‐box protein that is required for 60S ribosome biogenesis. To find the minimum functional length of the flanking regions, we have systematically designed truncation constructs and observed their effects on the growth of yeast cells in which endogenous Dbp6 has been depleted. Our results indicate that deletion of up to 168 amino acids at the N‐terminus (ΔN168) or 27 amino acids at the C‐terminus (ΔC27) give either wild‐type level or slow growth. However, removal of five more residues at the N‐terminus or two more at the C‐terminus results in a lethal phenotype. Interestingly, even though Dbp6 ΔN143 and Dbp6 ΔC21 each have near normal growth, the double truncation construct Dbp6 ΔN143ΔC21 has no growth. We are currently conducting Western blot analysis to confirm that Dbp6 is indeed being expressed in these yeast cells with growth phenotypes. Follow‐up experiments include measuring the ATP and/or RNA binding and RNA duplex unwinding activities of Dbp6 truncation constructs in vitro. Since most of the yeast DEAD‐box proteins have orthologs in humans and many of those proteins have been implicated in cancer development or progression, we hope that these insights into the molecular workings of Dbp6 can contribute to our broader understanding of DEAD‐box proteins and their uses as potential cancer therapeutic targets.Support or Funding InformationEckerd College Natural Sciences Summer Research Program (NSSRP)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Analysis of autophagy activated during changes in carbon source availability in yeast cells

Autophagy is a conserved intracellular degradation system in eukaryotes. Recent studies have revealed that autophagy can be induced not only by nitrogen starvation but also by many other stimuli. However, questions persist regarding the types of conditions that induce autophagy, as well as the particular kinds of autophagy that are induced under these specific conditions. In experimental studies, abrupt nutrient changes are often used to induce autophagy. In this study, we investigated autophagy induction in batch culture on low-glucose medium, in which growth of yeast (Saccharomyces cerevisiae) cells is clearly reflected exclusively by carbon source state. In this medium, cells pass sequentially through three stages: glucose-utilizing, ethanol-utilizing, and ethanol-depleted phases. Using GFP cleavage assay by immunoblotting methods, fluorescence microscopy, and transmission electron microscopy ultrastructural analysis, we found that bulk autophagy and endoplasmic reticulum-phagy are induced starting at the ethanol-utilizing phase, and bulk autophagy is activated to a greater extent in the ethanol-depleted phase. Furthermore, we found that mitophagy is induced by ethanol depletion. Microautophagy occurred after glucose depletion and involved incorporation of cytosolic components and lipid droplets into the vacuolar lumen. Moreover, we observed that autophagy-deficient cells grow more slowly in the ethanol-utilizing phase and exhibit a delay in growth resumption when they are shifted to fresh medium from the ethanol-depleted phase. Our findings suggest that distinct types of autophagy are induced in yeast cells undergoing gradual changes in carbon source availability.

Functional characterization of chaperonin containing T-complex polypeptide-1 and its conserved and novel substrates in Arabidopsis.

Chaperonin containing T-complex polypeptide-1 (CCT) is an evolutionarily conserved chaperonin multi-subunit complex that mediates protein folding in eukaryotes. It is essential for cell growth and survival in yeast and mammals, with diverse substrate proteins. However, only a few studies on plant CCT have been reported to date, due to the essentiality of CCT subunit genes and the large size of the complex. Here, we have investigated the structure and function of the Arabidopsis CCT complex in detail. The plant CCT consisted of eight subunits that assemble to form a high-molecular-mass protein complex, shown by diverse methods. CCT-deficient cells exhibited depletion of cortical microtubules, accompanied by a reduction in cellular α- and β-tubulin levels due to protein degradation. Cycloheximide-chase assays suggested that CCT is involved in the folding of tubulins in plants. Furthermore, CCT interacted with PPX1, the catalytic subunit of protein phosphatase 4, and may participate in the folding of PPX1 as its substrate. CCT also interacted with Tap46, a regulatory subunit of PP2A family phosphatases, but Tap46 appeared to function in PPX1 stabilization, rather than as a CCT substrate. Collectively, our findings reveal the essential functions of CCT chaperonin in plants and its conserved and novel substrates.

2-Alkyl-4-hydroxyquinolines from a Marine-Derived Streptomyces sp. Inhibit Hyphal Growth Induction in Candida albicans.

Four 2-alkyl-4-hydroxyquinoline derivatives (1–4) were isolated from a semisolid rice culture of the marine-derived actinomycete Streptomyces sp. MBTG13. The structures of these compounds were elucidated by a combination of spectroscopic methods, and their data were in good agreement with previous reports. Compounds 1 and 2 exhibited weak to moderate antibacterial activity against pathogenic bacteria. Unexpectedly, we found that compound 1 acted as a potent inhibitor of hyphal growth induction in the dimorphic fungus Candida albicans, with an IC50 value of 11.4 μg/mL. Growth experiments showed that this compound did not inhibit yeast cell growth, but inhibited hyphal growth induction. Semi-quantitative reverse transcription (RT)-PCR analysis of hyphal-inducing signaling pathway components indicated that compound 1 inhibited the expression of mRNAs related to the cAMP-Efg1 pathway. The expression of HWP1 and ALS3 mRNAs (hypha-specific genes positively regulated by Efg1, an important regulator of cell wall dynamics) was significantly inhibited by the addition of compound 1. These results indicate that compound 1 acts on the Efg1-mediated cAMP pathway and regulates hyphal growth in Candida albicans.

Repeated cultures of Saccharomyces cerevisiae SC90 to tolerate inhibitors generated during cassava processing waste hydrolysis for bioethanol production.

Large amount of cassava pulp is produced as by-product of industrial tapioca production. The value-added process of this low-cost waste is to use it as a substrate for bioethanol production. However, during the pulp pretreatment by acidification combined with steam explosion, many yeast inhibitors including acetic acid, formic acid, levulinic acid, furfural and 5-hydroxymethylfurfural are generated and these compounds have negative effects on the subsequent fermentation step. Therefore, the objective of this study was to investigate whether the repeated cultures of Saccharomyces cerevisiae SC90 could alleviate this problem. To obtain the inhibitor tolerable cells, the repeated culture was performed by growing yeast cells to a specific growth rate (µ) of 0.22h-1 or higher (80% of the µ in control) and then transferring them to progressively higher concentrations of hydrolysate ranging from 20 to 100% (v/v). The results showed a tendency of longer lag phase as well as time to reach maximum cell number (t maxc) with an increase in hydrolysate concentration. However, the repeated culture at the same hydrolysate concentration could shorten both lag period and t maxc. Interestingly, the growth and fermentation efficiency of adapted cells in 100% hydrolysate were significantly higher (p≤0.05) than those of non-adapted cells by 38% and 27%, respectively.

Effect of selenium on growth and antioxidative system of yeast cells

Selenium exhibits health-promoting properties in humans and animals. Therefore, the development of selenium-enriched dietary supplements has been growing worldwide. However, it may also exhibit toxicity at higher concentrations, causing increased oxidative stress. Different species of yeasts may exhibit different tolerances toward selenium. Therefore, in this study, we aimed to determine the effect of selenium on growth and on the antioxidative system in Candida utilis ATCC 9950 and Saccharomyces cerevisiae ATCC MYA-2200 yeast cells. The results of this study have demonstrated that high doses of selenium causes oxidative stress in yeasts, thereby increasing the process of lipid peroxidation. In addition, we obtained an increased level of GSSG from aqueous solutions of yeast biomass grown with selenium supplementation (40–60 mg/L). Increased levels of selenium in aqueous solutions resulted in an increase in the activity of antioxidant enzymes, including glutathione peroxidase and glutathione reductase. These results should encourage future research on the possibility of a thorough understanding of antioxidant system functioning in yeast cells.

An aggregation-prone mutant of eIF3a forms reversible assemblies escaping spatial control in exponentially growing yeast cells

Cells have elaborated a complex strategy to maintain protein homeostasis under physiological as well as stress conditions with the aim to ensure the smooth functioning of vital processes and producing healthy offspring. Impairment of one of the most important processes in living cells, translation, might have serious consequences including various brain disorders in humans. Here, we describe a variant of the translation initiation factor eIF3a, Rpg1-3, mutated in its PCI domain that displays an attenuated translation efficiency and formation of reversible assemblies at physiological growth conditions. Rpg1-3-GFP assemblies are not sequestered within mother cells only as usual for misfolded-protein aggregates and are freely transmitted from the mother cell into the bud although they are of non-amyloid nature. Their bud-directed transmission and the active movement within the cell area depend on the intact actin cytoskeleton and the related molecular motor Myo2. Mutations in the Rpg1-3 protein render not only eIF3a but, more importantly, also the eIF3 core complex prone to aggregation that is potentiated by the limited availability of Hsp70 and Hsp40 chaperones. Our results open the way to understand mechanisms yeast cells employ to cope with malfunction and aggregation of essential proteins and their complexes.