Hapen vaikutus leivinhiiva Saccharomyces cerevisiaen aineenvaihduntaan

The availability of oxygen has a major effect on all organisms. The yeast Saccharomyces cerevisiae is able to adapt its metabolism for growth in different conditions of oxygen provision, and to grow even under complete lack of oxygen. Although the physiology of S. cerevisiae has mainly been studied under fully aerobic and anaerobic conditions, less is known of metabolism under oxygen-limited conditions and of the adaptation to changing conditions of oxygen provision. This study compared the physiology of S. cerevisiae in conditions of five levels of oxygen provision (0, 0.5, 1.0, 2.8 and 20.9% O2 in feed gas) by using measurements on metabolite, transcriptome and proteome levels. On the transcriptional level, the main differences were observed between the three level groups, 0, 0.5 2.8 and 20.9% O2 which led to fully fermentative, respiro-fermentative and fully respiratory modes of metabolism, respectively. However, proteome analysis suggested post-transcriptional regulation at the level of 0.5 O2. The analysis of metabolite and transcript levels of central carbon metabolism also suggested post-transcriptional regulation especially in glycolysis. Further, a global upregulation of genes related to respiratory pathways was observed in the oxygen-limited conditions and the same trend was seen in the proteome analysis and in the activities of enzymes of the TCA cycle. The responses of intracellular metabolites related to central carbon metabolism and transcriptional responses to change in oxygen availability were studied. As a response to sudden oxygen depletion, concentrations of the metabolites of central carbon metabolism responded faster than the corresponding levels of gene expression. In general, the genome-wide transcriptional responses to oxygen depletion were highly similar when two different initial conditions of oxygen provision (20.9 and 1.0% O2) were compared. The genes related to growth and cell proliferation were transiently downregulated whereas the genes related to protein degradation and phosphate uptake were transiently upregulated. In the cultures initially receiving 1.0% O2, a transient upregulation of genes related to fatty acid oxidation, peroxisomal biogenesis, response to oxidative stress and pentose phosphate pathway was observed. Additionally, this work analysed the effect of oxygen on transcription of genes belonging to the hexose transporter gene family. Although the specific glucose uptake rate was highest in fully anaerobic conditions, none of the hxt genes showed highest expression in anaerobic conditions. However, the expression of genes encoding the moderately low affinity transporters decreased with the decreasing oxygen level. Thus it was concluded that there is a relative increase in high affinity transport in anaerobic conditions supporting the high uptake rate.Toisin kuin useimmat aitotumalliset eliöt, leivinhiiva Saccharomyces cerevisiae pystyy kasvamaan erilaisissa happipitoisuuksissa, jopa täysin hapettomissa oloissa. Tätä ominaisuutta on hyödennetty laajasti erilaisissa bioprosesseissa. Jotta näistä prosesseista saataisiin mahdollisimman tehokkaita, on tärkeä tietää, miten leivinhiivan aineenvaihduntaa säädellään hapen vaikutuksesta. Tässä väitöskirjatyössä tutkittiin leivinhiivan aineenvaihduntaa olosuhteissa, joissa syötetyn hapen määrä oli tarkasti määritetty. Työssä käytettiin viittä eri happipitoisuutta (0; 0,5; 1,0; 2,8 ja 20,9 % happea kasvatukseen syötetyssä kaasuseoksessa) sekä olosuhteita, joissa hapen syötttöä muutettiin äkillisesti. Työssä mitattiin solunsisäisiä ja -ulkoisia aineenvaihduntatuotteita ja geenien ilmentymistä. Hapensyötön eri tasoilla mitattiin myös proteiinien määriä ja entsyymien aktiivisuuksia. Geenien ilmentymisen ja solunulkoisten aineenvaihduntatuotteiden perusteella näytti siltä, että leivinhiivan aineenvaihdunta on hyvin samankaltaista rajoitetun hapen olosuhteissa (0,5; 1,0 ja 2,8 O2) mutta eroaa niissä selvästi hapettomista (0 % O2) ja normaalin hapen olosuhteista (20,9 % O2). Proteiinitasoja vertailtaessa kuitenkin havaittiin, että aineenvaihdunta ei ole täysin samanlaista happirajoitetuissa olosuhteissa. Erityisesti 0,5 ja 1,0 % hapensyötön välillä nähtiin eroja, mikä kertoo todenäköisesti geenitason yläpuolella tapahtuvasta säätelystä. Tässä työssä havaittiin myös, että suurin osa hengitykseen liittyistä geeneistä ilmentyi voimakkaammin happirajoitteisissa kuin normaalin hapen olosuhteissa, ja sama tulos näkyi myös kyseessä olevien proteiinien tasoissa ja sitruunahappokierron entsyymien aktiivisuuksissa. Tämä kertoo luultavasti siitä, että solu yrittää saada rajoitetun hapen mahdollisimman tehokkaasti käyttöönsä. Lisäksi havaittiin, että vaikka glukoosin sisäänottonopeus on suurin hapettomissa olosuhteissa, glukoosinkuljettajaproteiineja koodaavien geenien ilmentyminen ei ole tällöin voimakkaimmillaan. Sen sijaan hapen määrän laskiessa keskimääräisen affiniteetin omaavia glukoosinkuljettajia koodaavien geenien tasot laskivat. Edellä mainittu aiheuttaa todennäköisesti sen, että solukalvolla on hapettomissa olosuhteissa suhteellisesti enemmän proteiineja, joilla on korkea affiniteetti glukoosia kohtaan, kuin hapellisissa olosuhteissa. Lopetettaessa hapensyöttö äkillisesti kokonaan aineenvaihdunnan muutokset näkyivät nopeammin solunsisäisten aineenvaihduntatuotteiden määrissä kuin geenien ilmentymisessä. Havaittiin. että muutokset olivat hyvin samankaltaisia riippumatta siitä, kuinka paljon happea kasvatuksiin oli alun perin syötetty. Hapen loppuessa kasvuun ja solujen uudistumiseen liittyvien geenien ilmentymistasot laskivat, kun taas proteiinien hajotukseen liittyvien geenien ilmentymistasot nousivat. Lisäksi havaittiin stressivasteeseen liittyviä muutoksia

Low oxygen levels as a trigger for enhancement of respiratory metabolism in Saccharomyces cerevisiae

<p>Abstract</p> <p>Background</p> <p>The industrially important yeast <it>Saccharomyces cerevisiae </it>is able to grow both in the presence and absence of oxygen. However, the regulation of its metabolism in conditions of intermediate oxygen availability is not well characterised. We assessed the effect of oxygen provision on the transcriptome and proteome of <it>S. cerevisiae </it>in glucose-limited chemostat cultivations in anaerobic and aerobic conditions, and with three intermediate (0.5, 1.0 and 2.8% oxygen) levels of oxygen in the feed gas.</p> <p>Results</p> <p>The main differences in the transcriptome were observed in the comparison of fully aerobic, intermediate oxygen and anaerobic conditions, while the transcriptome was generally unchanged in conditions receiving different intermediate levels (0.5, 1.0 or 2.8% O₂) of oxygen in the feed gas. Comparison of the transcriptome and proteome data suggested post-transcriptional regulation was important, especially in 0.5% oxygen. In the conditions of intermediate oxygen, the genes encoding enzymes of the respiratory pathway were more highly expressed than in either aerobic or anaerobic conditions. A similar trend was also seen in the proteome and in enzyme activities of the TCA cycle. Further, genes encoding proteins of the mitochondrial translation machinery were present at higher levels in all oxygen-limited and anaerobic conditions, compared to fully aerobic conditions.</p> <p>Conclusion</p> <p>Global upregulation of genes encoding components of the respiratory pathway under conditions of intermediate oxygen suggested a regulatory mechanism to control these genes as a response to the need of more efficient energy production. Further, cells grown in three different intermediate oxygen levels were highly similar at the level of transcription, while they differed at the proteome level, suggesting post-transcriptional mechanisms leading to distinct physiological modes of respiro-fermentative metabolism.</p

Transcriptome of Saccharomyces cerevisiae during production of D-xylonate

BACKGROUND: Production of D-xylonate by the yeast S. cerevisiae provides an example of bioprocess development for sustainable production of value-added chemicals from cheap raw materials or side streams. Production of D-xylonate may lead to considerable intracellular accumulation of D-xylonate and to loss of viability during the production process. In order to understand the physiological responses associated with D-xylonate production, we performed transcriptome analyses during D-xylonate production by a robust recombinant strain of S. cerevisiae which produces up to 50 g/L D-xylonate. RESULTS: Comparison of the transcriptomes of the D-xylonate producing and the control strain showed considerably higher expression of the genes controlled by the cell wall integrity (CWI) pathway and of some genes previously identified as up-regulated in response to other organic acids in the D-xylonate producing strain. Increased phosphorylation of Slt2 kinase in the D-xylonate producing strain also indicated that D-xylonate production caused stress to the cell wall. Surprisingly, genes encoding proteins involved in translation, ribosome structure and RNA metabolism, processes which are commonly down-regulated under conditions causing cellular stress, were up-regulated during D-xylonate production, compared to the control. The overall transcriptional responses were, therefore, very dissimilar to those previously reported as being associated with stress, including stress induced by organic acid treatment or production. Quantitative PCR analyses of selected genes supported the observations made in the transcriptomic analysis. In addition, consumption of ethanol was slower and the level of trehalose was lower in the D-xylonate producing strain, compared to the control. CONCLUSIONS: The production of organic acids has a major impact on the physiology of yeast cells, but the transcriptional responses to presence or production of different acids differs considerably, being much more diverse than responses to other stresses. D-Xylonate production apparently imposed considerable stress on the cell wall. Transcriptional data also indicated that activation of the PKA pathway occurred during D-xylonate production, leaving cells unable to adapt normally to stationary phase. This, together with intracellular acidification, probably contributes to cell death. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2164-15-763) contains supplementary material, which is available to authorized users

Sosiaali- ja terveyspalvelut Suomessa 2018 : Asiantuntija-arvio

From information to assessment: aiming for better service

The intake of inorganic arsenic from long grain rice and rice-based baby food in Finland : Low safety margin warrants follow up

AbstractWe evaluated total and inorganic arsenic levels in long grain rice and rice based baby foods on Finnish market. Inorganic arsenic was analysed with an HPLC–ICP-MS system. The total arsenic concentration was determined with an ICP-MS method. In this study, the inorganic arsenic levels in long grain rice varied from 0.09 to 0.28mg/kg (n=8) and the total arsenic levels from 0.11 to 0.65mg/kg. There was a good correlation between the total and inorganic arsenic levels in long grain rice at a confidence level of 95%. The total arsenic levels of rice-based baby foods were in the range 0.02 – 0.29mg/kg (n=10), however, the level of inorganic arsenic could only be quantitated in four samples, on average they were 0.11mg/kg. Our estimation of inorganic arsenic intake from long grain rice and rice-based baby food in Finland indicate that in every age group the intake is close to the lowest BMDL0.1 value 0.3μg/kg bw/day set by EFSA. According to our data, the intake of inorganic arsenic should be more extensively evaluated

Kohdunkaulan, emättimen ja ulkosynnytinten solumuutokset : KÄYPÄ HOITO -SUOSITUS (Päivitystiivistelmä)

Käypä hoito -suositus. Päivitystiivistelm

Meeting the 24-h Movement Guidelines and Health-Related Outcomes Among Youth With Autism Spectrum Disorder: A Seven-Country Observational Study

Background: Meeting daily guidelines for physical activity, screen time, and sleep duration is associated with a host of health indicators for youth. In this cross-sectional observational study, we investigated the associations between adherence to the movement guidelines and health-related outcomes among youth with autism spectrum disorder (ASD). Methods: Parents of youth with ASD (10-17 years) from seven countries and regions were invited to provide online proxy-reports for child\u27s movement behaviors (i.e., physical activity, sleep and screen time), and health-related outcomes (i.e., body mass index [BMI], general health, and quality of life). A series of multiple linear regression analyses were used to examine the associations between meeting movement guidelines and health-related outcomes, adjusted for covariates. Results: The final sample consisted of 1165 youth with ASD. Compared with youth meeting all three guidelines, a higher BMI z-score was observed in those who met no guidelines (B = 0.62, P = 0.04), sedentary time only (B = 0.60, P = 0.047), and physical activity plus sleep only (B = 0.85, P = 0.04). Compared with meeting all three guidelines, meeting no guidelines was associated with poorer general health (B = - 0.46, P = 0.02). Further, compared with youth meeting all three guidelines, a lower quality of life score was observed in those who met no guidelines (B = - 0.47, P = 0.02) and physical activity only (B = - 0.62, P = 0.03). Lastly, there were dose-response associations between the number of guidelines met and all three health-related outcomes (all P(trend) \u3c 0.05). Conclusions: In conclusion, meeting more 24-h movement guidelines was generally associated with more favorable health-related outcomes in youth with ASD. The low level of adherence to all three guidelines (2.0%) suggests the urgent need to promote the adoption of all the guidelines in this group

Meeting the 24-hour movement guidelines and health-related outcomes among youth with autism spectrum disorder: a seven-country observational study

Background: Meeting daily guidelines for physical activity, screen time, and sleep duration is associated with a host of health indicators for youth. In this cross-sectional observational study, we investigated the associations between adherence to the movement guidelines and health-related outcomes among youth with autism spectrum disorder (ASD).Methods: Parents of youth with ASD (10–17 years) from seven countries and regions were invited to provide online proxy-reports for child’s movement behaviors (i.e., physical activity, sleep and screen time), and health-related outcomes (i.e., body mass index [BMI], general health, and quality of life). A series of multiple linear regression analyses were used to examine the associations between meeting movement guidelines and health-related outcomes, adjusted for covariates.Results: The final sample consisted of 1165 youth with ASD. Compared with youth meeting all three guidelines, a higher BMI z-score was observed in those who met no guidelines (B = 0.62, P = 0.04), “sedentary time only” (B = 0.60, P = 0.047), and “physical activity plus sleep only” (B = 0.85, P = 0.04). Compared with meeting all three guidelines, meeting no guidelines was associated with poorer general health (B = − 0.46, P = 0.02). Further, compared with youth meeting all three guidelines, a lower quality of life score was observed in those who met no guidelines (B = − 0.47, P = 0.02) and “physical activity only” (B = − 0.62, P = 0.03). Lastly, there were dose–response associations between the number of guidelines met and all three health-related outcomes (all Ptrend Conclusions: In conclusion, meeting more 24-h movement guidelines was generally associated with more favorable health-related outcomes in youth with ASD. The low level of adherence to all three guidelines (2.0%) suggests the urgent need to promote the adoption of all the guidelines in this group.</p