Trehalose metabolism in (hyper-) thermophilic Archaea

Die Rolle und Synthese von Trehalose sowie die Regulation der Trehalose-Synthese-Wege in Archaea ist bisher nicht völlig geklärt. In dieser Arbeit sollten der TPSP-Weg aus T. tenax, sowie der TreT/OrfY-Weg in den Crenarchaeota T. tenax, S. acidocaldarius und S. solfataricus untersucht werden, um eine mögliche Funktion von Trehalose als kompatibles Solut aufzuklären. Die T. tenax Trehalose-6-Phosphat Synthase/Phosphatase (TPSP) zeigt eine hohe Phosphatase-Aktivität, muss jedoch über die kotranskribierte Glykosyltransferase (GT) aktiviert werden um über die bifunktionale Synthase-Phosphatase-Aktivität zu verfügen. Dabei beruht die Aktivierung der TPS-Aktivität durch GT auf der Fusion der beiden Domänen (TPS und TPP) der TPSP. „Yeast two-Hybrid“-Experimente deuten auf eine Komplexbildung in vivo hin; somit könnte dieser Komplex je nach Bedarf gesteuert werden. Zusätzlich zu diesem einzigartigen Komplex wurden Hinweise auf einen mechanosensitiven Kanal gefunden, der sich wahrscheinlich auf Änderungen der Membranspannung hin öffnet und schließt. So konnte ein Modell für die Stressantwort in T. tenax erstellt werden. Unter Stresseinwirkung, wie der Erhöhung der Salzkonzentration im Medium, bilden TPSP und GT einen Komplex, was zur Synthese von Trehalose führt. Somit kann die Zelle vor Schäden durch die gesteigerte Osmolarität geschützt werden. Ändern sich die Umgebungsbedingungen, so ändert sich auch die Membranspannung der Zelle. In Folge dessen öffnet sich der mechanosensitive Kanal und hydrierte Solute, wie z.B. Trehalose können aus der Zelle ausgeschleust werden. Normalisiert sich die Membranspannung, so schließt sich der Kanal wieder. Der TreT/OrfY-Weg in T. tenax besteht aus der Trehalose Glykosyltranferrierenden Synthase (TreT) und einem offenen Leserahmen unbekannter Funktion (OrfY). Wie von Kouril et al. 2008 gezeigt wurde, ist die TTX_TreT unidirektional, kann also nur die Synthese von Trehalose katalysieren und diese nicht abbauen. Dabei ist die Aktivität der TreT unabhängig von OrfY. Auch in S. solfataricus und S. acidocaldarius wurden die Gene treT und orfY identifiziert; in S. acidocaldarius bilden sie ein Operon. Dies scheint einzigartig für Thermoproteales und Sulfolobales, sowie für einige Bakterien. Ein Schwerpunkt der Arbeit war die Untersuchung von OrfY. Die Kristallisierung des Proteins (Dr. J. Martin, Prof. Dr. A. Lupas, MPI Tübingen) zeigte, dass das Protein OrfY eine völlig neuartige Faltung besitzt. OrfY besteht aus zwei nahezu identischen Domänen, die in HHpred Vorhersagen als TetR-Transkriptionsregulator-ähnliche Helix-turn-Helix (HTH)-Domänen identifiziert wurden. Ähnliche, jedoch nicht duplizierte HTH-Domänen finden sich neben den OrfY Homologen aus Bakterien und Archaea ebenfalls in Amylasen, PEP bindenden Proteinen, die teilweise als PEP Synthasen oder Pyruvat-Phosphat-Dikinasen oder Antwort Regulatoren annotiert sind, wie auch in Proteinen unbekannter Funktion aus thermoacidophilen Organismen und proteinkodierenden Sequenzen aus Metagenomprojekten. Strukturvergleiche zeigten konservierte Reste (H49/157 und D67/171), die ein aktives Zentrum bilden könnten, welches durch die Aromaten F12/120 und W71/175 vermutlich stabilisiert wird. Dies deutet auf eine enzymatische Aktivität hin. Es konnte gezeigt werden, dass die Gegenwart von Trehalose oder Glukose die Oligomerisierung von OrfY beeinflussen. Des Weiteren wurde übereinstimmend mit der HTH-Domänenstruktur eine starke DNA-Bindung beobachtet. Die Ergebnisse deuten darauf hin, dass OrfY einerseits Zucker binden und eventuell auch enzymatisch umsetzen kann, zum anderen als Helix-turn-Helix-Domänen-Protein aber auch DNA binden könnte. In den beiden untersuchten Sulfolobus Spezies findet sich zusätzlich zum TreT/OrfY-Weg ein zweiter Weg zur Trehalose-Synthese, der TreY/TreZ-Weg (Lama, 1990; Maruta, 1996). Für beide Organismen wurden Deletiosnmutanten konstruiert (MW001∆orfY, MW001∆treT, MW001∆treY, MW001∆orfY∆treT, MW001∆orfY∆treY, MW001∆treT∆treY und MW001∆treY∆orfY∆treT, bzw. S. solfataricus PBL2025∆treT), deren Wachstum unter verschiedenen Stressoren (erhöhte Salzkonzentration ((250 mM KCl, bzw. 300 mM NaCl) initial oder ab der logarithmischen-Wachstumsphase zugegeben (in S. acidocaldarius), bzw. 200 mM – 700 mM NaCl, initial zugegeben (bei S. solfataricus) , so wie eine erhöhte Wachstumstemperatur von 83, bzw. 85°C) untersucht wurde. Durch diese Experimente konnte gezeigt werden, dass Trehalose für beide Organismen unter Salzstress (besonders NaCl) wichtig ist. Sowohl der TreT/OrfY- als auch der TreY/TreZ-Weg sind essentiell für eine Stressantwort; es scheint keinen weiteren Trehalose-Synthese-Weg in diesen Organismen zu geben. In dieser Studie konnte gezeigt werden, dass OrfY eine Rolle bei der Bildung von Trehalose spielt. Des Weiteren zeigte sich, dass sowohl Mutanten ohne orfY, als auch ohne treT einen veränderten Phänotyp gegenüber dem Wildtyp unter Stresseinwirkung ausweisen, was bedeutet, dass sowohl TreT als auch OrfY für einen funktionellen TreT/OrfY-Weg essentiell sind. Dabei könnte OrfY eine regulatorische Funktion haben, was zu den HHpred Vorhersagen des TTX_OrfYs passt. Die Versuche legen nahe, dass der TreT/OrfY-Weg wie auch der TreY/TreZ-Weg nicht konstitutiv genutzt wird, sondern beide Wege Wachstumsphasen abhängig sind. Um dies weiter zu untersuchen, müssen Rohextrakt-Analysen mit Zellen aus verschiedenen Wachstumsphasen durchgeführt werden. Die Trehalose-Synthese scheint also in den beiden Sulfolobus Spezies unter Stressbedingungen induziert zu werden und das Disaccharid als kompatibles Solut zu fungieren.The role of trehalose and its synthesis as well as the regulation of the pathways for trehalose-synthesis are not fully understood. The aim of the presented work was the investigation of the TPSP-pathway in T. tenax and the TreT/OrfY-pathway in the Crenarchaeota T. tenax, S. acidocaldarius and S. solfataricus in order to find a possible function of trehalose as compatible solute. The T. tenax trehalose-6-phosphate synthase/phosphatase (TPSP) shows high phosphatase-activity, however, the enzyme must be activated by the cotranscribed glycosyltransferase (GT) to comprise the full bifunctional synthase-phosphatase-activity. Thereby the activation of the TPS-activity by GT is based on the fusion of both domains (TPS and TPP) of the TPSP. „Yeast two-Hybrid“-experiments point to a complexation in vivo; hence, this complex might be regulated depending on the demand. Additional to this unique complex, there are evidences for a mechanosensitive channel, probably reacting to changes of the membrane tension by opening and closing. This way a model for the stress response in T. tenax was constructed. Within a stress situation, like the increase of salinity in the medium, TPSP and GT build a complex, leading to the synthesis auf trehalose. According to this, the cell is protected against damages by high osmolarity. When the environmental conditions change also the membrane tension changes, followed by the opening of the mechanosensitive channel. This way, hydrated solutes, e.g. trehalose, can flush out of the cell. After normalizing the membrane tension, the channel closes again. The TreT/OrfY-pathway in T. tenax comprises a trehalose glycosyl transferring synthase (TreT) and an open reading frame of unknown function (OrfY). As shown by Kouril et al. 2008, the TTX_TreT is unidirectional, only catalyzing the synthesis of trehalose. Here, the activity of TreT is independent from OrfY. Also in S. solfataricus and S. acidocaldarius the genes treT und orfY were identified; in S. acidocaldarius they are located within an operon. This seems to be unique for the Thermoproteales and Sulfolobales, as well as for some Bacteria. A milestone of this work was the examination of OrfY. The crystallization of the protein (Dr. J. Martin, Prof. Dr. A. Lupas, MPI Tübingen) showed, that the protein OrfY comprises a totally new folding. OrfY consist of two almost identical domains that show, according to predictions from HHpred, Helix-turn-Helix (HTH)-like domains with similarities to TetR-transcriptional regulators. Similar but not duplicated HTH-domains are amongst OrfY homologues in Bacteria and Archaea. These are also found in amylases, PEP-binding proteins annotated on the one hand as PEP-synthases and on the other hand as pyruvate-phosphate-dikinases or response regulators. The motif can also be found in proteins of thermoacidophilic organisms with unknown function and protein-coding sequences from metagenomic projects. Structural comparisons show conserved residues (H49/157 and D67/171), maybe building the active site, that presumably is stabilized by the aromates F12/120 and W71/175. All these facts point to an enzymatic activity. It was demonstrated, that the presence of trehalose and glucose affects the oligomerization of OrfY. Corresponding to the HTH-domain structure, a strong DNA-binding could be observed. The results indicate, that on the one hand OrfY binds and maybe even enzymatically converts sugar and on the other hand that the Helix-turn-Helix-domain protein also might bind to DNA. In both examined Sulfolobus species a second way for trehalose synthesis despite the TreT/OrfY-pathway is found: the TreY/TreZ-pathway (Lama, 1990; Maruta, 1996). For both organisms deletion-mutants were constructed (MW001∆orfY, MW001∆treT, MW001∆treY, MW001∆orfY∆treT, MW001∆orfY∆treY, MW001∆treT∆treY und MW001∆treY∆orfY∆treT, respectively S. solfataricus PBL2025∆treT). The growth was monitored under different stressors (elevated salt concentration (S. acidocaldarius: 250 mM KCl or 300 mM NaCl, respectively added initial or in the logarithmical growth phase, respectively; S. solfataricus: 200 mM – 700 mM NaCl added initial), as well as an increased growth temperature of 83 or 85°C, respectively). The experiments showed that trehalose is very important for both organisms under salt stress (especially NaCl). The TreT/OrfY- as well as the TreY/TreZ-pathway are essential for the stress response. It seems that there is no other trehalose-synthesis-pathway in these organisms. This study showed that OrfY plays a role in the formation of trehalose. Additionally, it could be shown, that mutants lacking orfY or treT, respectively, show an altered phenotype under stress conditions compared to the wildtype, pointing to the conclusion that TreT and OrfY are essential for a functional TreT/OrfY-pathway. OrfY might have a regulatory function, fitting to the HHpred predictions. The results indicate that the TreT/OrfY-pathway and the TreY/TreZ-pathway are not used constitutively but are growth phase dependent. To get further information crude extract analysis with cells from different growth phases should be performed. The trehalose-synthesis seems to be induced in both Sulfolobus species under stress conditions and the disaccharide appears to function as compatible solute

Disentangling the Effects of Processing Speed on the Association between Age Differences and Fluid Intelligence

Several studies have demonstrated that individual differences in processing speed fully mediate the association between age and intelligence, whereas the association between processing speed and intelligence cannot be explained by age differences. Because measures of processing speed reflect a plethora of cognitive and motivational processes, it cannot be determined which specific processes give rise to this mediation effect. This makes it hard to decide whether these processes should be conceived of as a cause or an indicator of cognitive aging. In the present study, we addressed this question by using a neurocognitive psychometrics approach to decompose the association between age differences and fluid intelligence. Reanalyzing data from two previously published datasets containing 223 participants between 18 and 61 years, we investigated whether individual differences in diffusion model parameters and in ERP latencies associated with higher-order attentional processing explained the association between age differences and fluid intelligence. We demonstrate that individual differences in the speed of non-decisional processes such as encoding, response preparation, and response execution, and individual differences in latencies of ERP components associated with higher-order cognitive processes explained the negative association between age differences and fluid intelligence. Because both parameters jointly accounted for the association between age differences and fluid intelligence, age-related differences in both parameters may reflect age-related differences in anterior brain regions associated with response planning that are prone to be affected by age-related changes. Conversely, age differences did not account for the association between processing speed and fluid intelligence. Our results suggest that the relationship between age differences and fluid intelligence is multifactorially determined

Do Attentional Lapses Account for the Worst Performance Rule?

The worst performance rule (WPR) describes the phenomenon that individuals’ slowest responses in a task are often more predictive of their intelligence than their fastest or average responses. To explain this phenomenon, it was previously suggested that occasional lapses of attention during task completion might be associated with particularly slow reaction times. Because less intelligent individuals should experience lapses of attention more frequently, reaction time distribution should be more heavily skewed for them than for more intelligent people. Consequently, the correlation between intelligence and reaction times should increase from the lowest to the highest quantile of the response time distribution. This attentional lapses account has some intuitive appeal, but has not yet been tested empirically. Using a hierarchical modeling approach, we investigated whether the WPR pattern would disappear when including different behavioral, self-report, and neural measurements of attentional lapses as predictors. In a sample of N = 85, we found that attentional lapses accounted for the WPR, but effect sizes of single covariates were mostly small to very small. We replicated these results in a reanalysis of a much larger previously published data set. Our findings render empirical support to the attentional lapses account of the WPR

Erwerbstätigkeit jenseits der Rentengrenze: Erfahrung und Deutung erwerbsbezogener Handlungsspielräume im Alter

"Der Artikel untersucht und vergleicht die Gründe für Erwerbstätigkeit jenseits der Rentengrenze aus der subjektiven Perspektive von arbeitenden Rentnerinnen und Rentnern sowie von Expertinnen und Experten, die sozialpolitische Akteure vertreten. Grundlage sind in Deutschland und Großbritannien geführte qualitative Interviews. Arbeitende Ältere schildern eine Vielzahl von Gründen für ihre Tätigkeit, besonders Freude an der Arbeit und soziale Kontakte. Finanzielle Motive fürs Arbeiten sind vielfältig und lassen sich nicht auf finanzielle Not reduzieren. Insgesamt überwiegt die positive Erfahrung der Tätigkeit vor dem Hintergrund des entpflichteten Ruhestands, der durch die Erwerbstätigkeit aktiv gestaltet wird. Die Expertinnen und Experten ordnen die von ihnen ausgemachten vielfältigen Gründe für Arbeit im Rentenalter, dichotomisieren sie teilweise (in Zwang oder Wahl) und quantifizieren ihr Vorkommen. Dies ist die Grundlage für ihre Wertungen und politischen Folgerungen. Wir diskutieren die Unterschiede zwischen den Perspektiven der arbeitenden Älteren und der Fachleute im Kontext der institutionellen Formierung von Handlungsspielräumen, der Deutung individuellen Handelns in individualisierten Gesellschaften und der an Aktivierung orientierten Neuverhandlung der Lebensphase Alter. Erwerbstätigkeit im Rentenalter wird bisher kaum als Zwang und Folge eingeschränkter finanzieller Handlungsspielräume erfahren. Die durch die Fachleute vorgenommene Gleichsetzung von finanziellen Motiven und Notwendigkeit des Arbeitens findet sich in den Sichtweisen der Älteren kaum. Gleichzeitig übersehen die Fachleute Handlungseinschränkungen der Älteren, die diese in Hinblick auf ihre Arbeitsgelegenheiten ausmachen. Sowohl in den Deutungen der Fachleute als auch in denen der arbeitenden Älteren schlagen sich auf Aktivierung zielende Neudeutungen des Ruhestands nieder, die neue soziale Ungleichheiten mit sich bringen könnten." (Autorenreferat

Fluid Intelligence Is (Much) More than Working Memory Capacity: An Experimental Analysis

Empirical evidence suggests a great positive association between measures of fluid intelligence and working memory capacity, which implied to some researchers that fluid intelligence is little more than working memory. Because this conclusion is mostly based on correlation analysis, a causal relationship between fluid intelligence and working memory has not yet been established. The aim of the present study was therefore to provide an experimental analysis of this relationship. In a first study, 60 participants worked on items of the Advanced Progressive Matrices (APM) while simultaneously engaging in one of four secondary tasks to load specific components of the working memory system. There was a diminishing effect of loading the central executive on the APM performance, which could explain 15% of the variance in the APM score. In a second study, we used the same experimental manipulations but replaced the dependent variable with complex working memory span tasks from three different domains. There was also a diminishing effect of the experimental manipulation on span task performance, which could now explain 40% of the variance. These findings suggest a causal effect of working memory functioning on fluid intelligence test performance, but they also imply that factors other than working memory functioning must contribute to fluid intelligence

Identification and simulation of surface alpha events on passivated surfaces of germanium detectors and the influence of metalisation

Events from alpha interactions on the surfaces of germanium detectors are a major contribution to the background in germanium-based searches for neutrinoless double-beta decay. Surface events are subject to charge trapping, affecting their pulse shape and reconstructed energy. A study of alpha events on the passivated end-plate of a segmented true-coaxial n-type high-purity germanium detector is presented. Charge trapping is analysed in detail and an existing pulse-shape analysis technique to identify alpha events is verified with mirror pulses observed in the non-collecting channels of the segmented test detector. The observed radial dependence of charge trapping confirms previous results. A dependence of the probability of charge trapping on the crystal axes is observed for the first time. A first model to describe charge trapping effects within the framework of the simulation software SolidStateDetectors.jl is introduced. The influence of metalisation on events from low-energy gamma interactions close to the passivated surface is also presented

Priorities and barriers for urban ecosystem service provision: A comparison of stakeholder perspectives from three cities

Urban Green Infrastructure (UGI) can provide many needed ecosystem services (ES) to help address challenges like biodiversity loss and climate change while contributing to the health and wellbeing of urban inhabitants. In order to optimize UGI for a given city, a first step is to assess the local ES needs and the potential barriers to ES provision. However, it is not known how consistent these needs and barriers are among cities in different settings. To help address this knowledge gap, the aim of this study was to assess ES priorities and existing barriers to ES provision for three cities varying in socioeconomic, cultural and climatic setting: Addis Ababa (Ethiopia), Cincinnati (USA) and Malmö (Sweden). In case studies of each of the three cities, we carried out workshops with key stakeholders and collected their assessments of both current provision of ES from UGI and future priorities. The workshops were followed by expert stakeholder interviews aimed at highlighting existing barriers to ES provision. In spite of the different urban contexts, expressed ES priorities were similar among the cities, with the highest cross-cutting priorities being climate change adaptation, stormwater runoff management and water quality, mental and physical health, biodiversity, and provision of local food. Stakeholder-expressed barriers to ES provision were also broadly similar among cities, falling into three main categories: structural pressures, gaps in governance, and lack of ecological awareness and vision. Our results suggest that certain key ES priorities and barriers may apply broadly to cities regardless of climatic or socio-cultural context. These generic needs can help direct the focus of future studies, and imply a clear benefit to international, even cross-continental study and knowledge-exchange among practitioners and researchers working with UGI

Using CoCu2_2Ga/SiO2_2 to identify stability-issues in ethanol-selective Co-Cu alloyed catalysts in carbon monoxide hydrogenation

Hydrogenation of CO to higher alcohols such as ethanol is an attractive pathway for industrial production while avoiding competition with food crops. However, thermocatalytic ethanol production from syngas is currently hindered by the lack of selective catalysts. The structural integrity of ternary-alloyed CoCu2Ga nanoparticles supported on silica was studied during thermo-catalytic CO hydrogenation. Catalysts of four different CoCu$_2$Ga weight-loadings were tested catalytically under differential conversion, showing their different intrinsic selectivity during CO hydrogenation towards ethanol, methanol, and hydrocarbons. CoCu$_2$Ga catalysts with 3.5 wt% and 17.8 wt% proved most and least selective towards ethanol formation, respectively. These two were studied in depth using STEM-EDX of fresh and spent samples showing different size distributions of the nanoparticles for all samples, and a change in the Co/Cu distribution of the nanoparticles from fresh to spent samples. In situ characterization using XRD, XANES, and EXAFS during CO hydrogenation supported the findings of the STEM-EDX and elucidated that the fresh more homogenous catalyst consisting of ternary CoCu$_2$Ga nanoparticles de-alloyed into Cu-rich and CoGa-rich nanoparticles. This de-alloying was possibly driven by two factors: the metastable phase of CoCu$_2$Ga decreasing its free energy by separating Cu and Co; and the strong interaction between Co and CO further driving a segregation. From a theoretical standpoint, Cu-Co intermetallics present the most selective catalyst to form ethanol over methane and methanol. The experimental findings presented here support the theory, although further efforts are needed to improve structural stability during the catalytic reaction

Temperature Dependence of the Electron-Drift Anisotropy and Implications for the Electron-Drift Model

The electron drift in germanium detectors is modeled making many assumptions. Confronted with data, these assumptions have to be revisited. The temperature dependence of the drift of electrons was studied in detail for an n-type segmented point-contact germanium detector. The detector was mounted in a temperature controlled, electrically cooled cryostat. Surface events were induced with collimated 81 keV photons from a $^{133}$Ba source. A detailed analysis of the rise time of pulses collected in surface scans, performed at different temperatures, is presented. The longitudinal anisotropy of the electron drift decreases with rising temperature. A new approach, making use of designated rise-time windows determined by simulations using SolidStateDetectors.jl, was used to isolate the longitudinal drift of electrons along different axes to quantify this observation. The measured temperature dependence of the longitudinal drift velocities combined with the standard electron drift model as widely used in relevant simulation packages results in unphysical predictions. A first suggestion to modify the electron-drift model is motivated and described. The results of a first implementation of the modified model in SolidStateDetectors.jl are shown. They describe the data reasonably well. A general review of the model and the standard input values for mobilities is suggested

First feed matters: The first diet of larval fish programmes growth, survival, and metabolism of larval ballan wrasse (Labrus bergylta)

The use of cleaner fish, such as the ballan wrasse (Labrus bergylta), is important for combatting the sea lice problem in salmonid cage farming. Ballan wrasse is the only wrasse species that is cultivated, though only about 50% of the approx. 3 million ballan wrasse used in 2020 was produced by aquaculture. The major obstacle for large scale cultivation of ballan wrasse is the difficult first feeding phase and a lack of functional feeding protocols. Like most pelagic marine fish larvae, ballan wrasse do not accept inert diets as first feed, and feeding regimes based on rotifers and Artemia (brine shrimps) usually lead to mixed results and are far from being optimal nutrition for the larvae. In a 48-day start feeding experiment, we studied the feasibility of replacing rotifers by an Experimental cirriped diet or copepod nauplii (Acartia tonsa) and replacing Artemia by nauplii of the cirriped Semibalanus balanoides. Later, all treatments received the same formulated diets. We sampled larvae at each feed transition to analyze different response variables such as growth, morphometry, gene expression, lipidomics, histology, and microbiology. We found significant differences in survival rates and growth. Larvae fed copepods as the first diet had significantly higher survival rates than larvae start-fed on either rotifers or small experimental cirripeds, and this pattern was also reflected in early growth and bone development. Gut histology at the end of the experiment (48 days after hatching) showed a more developed intestinal tissue in the larval group fed copepods first and cirripeds as the second diet compared to the other larval groups. Gene expression at day 48 post hatch still revealed pronounced differences between the larval group first fed on rotifers and larvae from the other three feeding regimes which received natural, unenriched diets. Even weeks after receiving the same formulated diets, lipidomics analyses revealed that several lipid species correlated either negatively or positively with larval growth rates or mortality. Our results are a clear indication for nutritional programming, pointing towards the importance the first diet has for the further life of a fish.publishedVersio