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11.
Influence of pH and Temperature on Enumeration of Cellulose- and Hemicellulose-Degrading Thermophilic Anaerobes in Neutral and Alkaline Icelandic Hot Springs 下载免费PDF全文
Indra M. Mathrani Peter Nielsen Jacob Sonne-Hansen Jakob K. Kristjnsson Birgitte K. Ahring 《Applied microbiology》1993,59(6):1963-1965
Cellulose- and hemicellulose-degrading thermophilic anaerobes were enumerated in biomat samples of various temperatures from two different hot springs in the Hveragerǒi area of Iceland: one spring had a pH near 7, the second had a pH near 9. The most-probable-number technique was used for enumeration of bacteria in the samples, with media at many different temperatures (37 to 90°C) and two pH values (7 and 9). There were generally more xylan-degrading then cellulose-utilizing organisms in both environments. There was no growth at 80°C in the neutral spring or at 37°C in the alkaline spring. However, there were large numbers of both types of organisms in the alkaline spring at 80°C and in the neutral spring at 37°C. No cultures grew from the most-probable-number tubes inoculated with the Hveragerǒi samples and incubated at 90°C or with media at pH 9. However, xylan-degrading cultures at 70°C were enriched at pH 9 with samples from some other Icelandic hot springs. 相似文献
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Krešimir Begović Jonathan S. Schurman Marek Svitok Jakob Pavlin Thomas Langbehn Kristyna Svobodová Martin Mikoláš Pavel Janda Michal Synek William Marchand Lucie Vitková Daniel Kozák Ondrej Vostarek Vojtech Čada Radek Bače Miroslav Svoboda 《Global Change Biology》2023,29(1):143-164
In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks. 相似文献
14.
Hui Yang Seth M. Munson Chris Huntingford Nuno Carvalhais Alan K. Knapp Xiangyi Li Josep Peñuelas Jakob Zscheischler Anping Chen 《Global Change Biology》2023,29(8):2351-2362
Negative extreme anomalies in vegetation growth (NEGs) usually indicate severely impaired ecosystem services. These NEGs can result from diverse natural and anthropogenic causes, especially climate extremes (CEs). However, the relationship between NEGs and many types of CEs remains largely unknown at regional and global scales. Here, with satellite-derived vegetation index data and supporting tree-ring chronologies, we identify periods of NEGs from 1981 to 2015 across the global land surface. We find 70% of these NEGs are attributable to five types of CEs and their combinations, with compound CEs generally more detrimental than individual ones. More importantly, we find that dominant CEs for NEGs vary by biome and region. Specifically, cold and/or wet extremes dominate NEGs in temperate mountains and high latitudes, whereas soil drought and related compound extremes are primarily responsible for NEGs in wet tropical, arid and semi-arid regions. Key characteristics (e.g., the frequency, intensity and duration of CEs, and the vulnerability of vegetation) that determine the dominance of CEs are also region- and biome-dependent. For example, in the wet tropics, dominant individual CEs have both higher intensity and longer duration than non-dominant ones. However, in the dry tropics and some temperate regions, a longer CE duration is more important than higher intensity. Our work provides the first global accounting of the attribution of NEGs to diverse climatic extremes. Our analysis has important implications for developing climate-specific disaster prevention and mitigation plans among different regions of the globe in a changing climate. 相似文献
15.
Jakob Noske Josef Paul Kynast Dominik Lemm Steffen Schmidt Birte Höcker 《Protein science : a publication of the Protein Society》2023,32(1):e4516
The ability to design customized proteins to perform specific tasks is of great interest. We are particularly interested in the design of sensitive and specific small molecule ligand-binding proteins for biotechnological or biomedical applications. Computational methods can narrow down the immense combinatorial space to find the best solution and thus provide starting points for experimental procedures. However, success rates strongly depend on accurate modeling and energetic evaluation. Not only intra- but also intermolecular interactions have to be considered. To address this problem, we developed PocketOptimizer, a modular computational protein design pipeline, that predicts mutations in the binding pockets of proteins to increase affinity for a specific ligand. Its modularity enables users to compare different combinations of force fields, rotamer libraries, and scoring functions. Here, we present a much-improved version––PocketOptimizer 2.0. We implemented a cleaner user interface, an extended architecture with more supported tools, such as force fields and scoring functions, a backbone-dependent rotamer library, as well as different improvements in the underlying algorithms. Version 2.0 was tested against a benchmark of design cases and assessed in comparison to the first version. Our results show how newly implemented features such as the new rotamer library can lead to improved prediction accuracy. Therefore, we believe that PocketOptimizer 2.0, with its many new and improved functionalities, provides a robust and versatile environment for the design of small molecule-binding pockets in proteins. It is widely applicable and extendible due to its modular framework. PocketOptimizer 2.0 can be downloaded at https://github.com/Hoecker-Lab/pocketoptimizer . 相似文献
16.
Anti-predator defence behaviour of Holocnemus pluchei (Araneae, Pholcidae) was studied in the laboratory and the field. Bouncing, in which this web-building spider moves its body rapidly up and down while keeping its legs on the silk, was the most frequent response to disturbance. Less often, H. pluchei left the web when disturbed. Experiments were carried out to determine the types of stimuli that elicited bouncing and leaving the web: tactile stimulation (striking the spider with a brush) and air movement (blowing on the spider) elicited bouncing and leaving the web, but there was no evidence that chemical stimuli from potential predators were important. Tactile stimulation elicited stronger responses than air movement. There were no evident differences in how H. pluchei responded to tactile stimulation in the laboratory and the field. 相似文献
17.
Karoline Schousboe Gonneke Willemsen Kirsten O Kyvik Jakob Mortensen Dorret I Boomsma Belinda K Cornes Chayna J Davis Corrado Fagnani Jacob Hjelmborg Jaakko Kaprio Marlies De Lange Michelle Luciano Nicholas G Martin Nancy Pedersen Kirsi H Pietil?inen Aila Rissanen Suoma Saarni Thorkild I A S?rensen G Caroline M Van Baal Jennifer R Harris 《Twin research》2003,6(5):409-421
Body mass index (BMI), a simple anthropometric measure, is the most frequently used measure of adiposity and has been instrumental in documenting the worldwide increase in the prevalence of obesity witnessed during the last decades. Although this increase in overweight and obesity is thought to be mainly due to environmental changes, i.e., sedentary lifestyles and high caloric diets, consistent evidence from twin studies demonstrates high heritability and the importance of genetic differences for normal variation in BMI. We analysed self-reported data on BMI from approximately 37,000 complete twin pairs (including opposite sex pairs) aged 20-29 and 30-39 from eight different twin registries participating in the GenomEUtwin project. Quantitative genetic analyses were conducted and sex differences were explored. Variation in BMI was greater for women than for men, and in both sexes was primarily explained by additive genetic variance in all countries. Sex differences in the variance components were consistently significant. Results from analyses of opposite sex pairs also showed evidence of sex-specific genetic effects suggesting there may be some differences between men and women in the genetic factors that influence variation in BMI. These results encourage the continued search for genes of importance to the body composition and the development of obesity. Furthermore, they suggest that strategies to identify predisposing genes may benefit from taking into account potential sex specific effects. 相似文献
18.
Karri Silventoinen Sampo Sammalisto Markus Perola Dorret I Boomsma Belinda K Cornes Chayna Davis Leo Dunkel Marlies De Lange Jennifer R Harris Jacob V B Hjelmborg Michelle Luciano Nicholas G Martin Jakob Mortensen Lorenza Nisticò Nancy L Pedersen Axel Skytthe Tim D Spector Maria Antonietta Stazi Gonneke Willemsen Jaakko Kaprio 《Twin research》2003,6(5):399-408
A major component of variation in body height is due to genetic differences, but environmental factors have a substantial contributory effect. In this study we aimed to analyse whether the genetic architecture of body height varies between affluent western societies. We analysed twin data from eight countries comprising 30,111 complete twin pairs by using the univariate genetic model of the Mx statistical package. Body height and zygosity were self-reported in seven populations and measured directly in one population. We found that there was substantial variation in mean body height between countries; body height was least in Italy (177 cm in men and 163 cm in women) and greatest in the Netherlands (184 cm and 171 cm, respectively). In men there was no corresponding variation in heritability of body height, heritability estimates ranging from 0.87 to 0.93 in populations under an additive genes/unique environment (AE) model. Among women the heritability estimates were generally lower than among men with greater variation between countries, ranging from 0.68 to 0.84 when an additive genes/shared environment/unique environment (ACE) model was used. In four populations where an AE model fit equally well or better, heritability ranged from 0.89 to 0.93. This difference between the sexes was mainly due to the effect of the shared environmental component of variance, which appears to be more important among women than among men in our study populations. Our results indicate that, in general, there are only minor differences in the genetic architecture of height between affluent Caucasian populations, especially among men. 相似文献
19.
Active Site Mutations in Yeast Protein Disulfide Isomerase Cause Dithiothreitol Sensitivity and a Reduced Rate of Protein Folding in the Endoplasmic Reticulum 总被引:7,自引:0,他引:7 下载免费PDF全文
Aspects of protein disulfide isomerase (PDI) function have been studied in yeast in vivo. PDI contains two thioredoxin-like domains, a and a′, each of which contains an active-site CXXC motif. The relative importance of the two domains was analyzed by rendering each one inactive by mutation to SGAS. Such mutations had no significant effect on growth. The domains however, were not equivalent since the rate of folding of carboxypeptidase Y (CPY) in vivo was reduced by inactivation of the a domain but not the a′ domain. To investigate the relevance of PDI redox potential, the G and H positions of each CGHC active site were randomly mutagenized. The resulting mutant PDIs were ranked by their growth phenotype on medium containing increasing concentrations of DTT. The rate of CPY folding in the mutants showed the same ranking as the DTT sensitivity, suggesting that the oxidative power of PDI is an important factor in folding in vivo. Mutants with a PDI that cannot perform oxidation reactions on its own (CGHS) had a strongly reduced growth rate. The growth rates, however, did not correlate with CPY folding, suggesting that the protein(s) required for optimal growth are dependent on PDI for oxidation. pdi1-deleted strains overexpressing the yeast PDI homologue EUG1 are viable. Exchanging the wild-type Eug1p C(L/I)HS active site sequences for C(L/I)HC increased the growth rate significantly, however, further highlighting the importance of the oxidizing function for optimal growth. 相似文献
20.
Changes in chromatin structure at the replication fork. II The DNPs containing nascent DNA and a transient chromatin modification detected by DNAase I. 总被引:2,自引:1,他引:1 下载免费PDF全文
Discrete deoxyribonucleoproteins (DNPs) containing nascent and/or bulk DNA, were obtained by fractionating micrococcal nuclease digests of nuclei form 3H-thymidine pulse (15-20 sec) and 14C-thymidine long (16 h) labeled sea urchin embryos in polyacrylamide gels. One of these DNPs was shown to contain the micrococcal nuclease resistant 300 bp "large nascent DNA" described in Cell 14, 259-267, 1978. The bulk and nascent mononucleosome fractions provided evidence for the preferential digestion by micrococcal nuclease of nascent over bulk linker regions to yield mononucleosome cores with nascent DNA. DNAase I was used to probe whether any nascent DNA is in nucleosomes. Nascent as well as bulk single-stranded DNA fragments occurred in multiples of 10.4 bases with higher than random frequencies of certain fragment sizes (for instance 83 bases) as expected from a nucleosome structure. However, a striking background of nascent DNA between nascent DNA peaks was observed. This was eliminated by a pulse-chase treatment or by digestion of pulse-labeled nuclei with micrococcal nuclease together with DNAase I. One of several possible interpretations of these results suggests that a transient change in nucleosome structure may have created additional sites for the nicking of nascent DNA by DNAase I; the micrococcal nuclease sensitivity of the interpeak radioactivity suggest its origin from the linker region. Endogenous nuclease of sea urchin embryos cleaves chromatin DNA in a manner similar to that of DNAase I. 相似文献