Long-term acclimation might enhance the growth and competitive ability of Microcystis aeruginosa in warm environments

1. The positive effect of global warming on the growth of cyanobacteria has been widely predicted, but long-term studies targeting their adaptive potential to higher temperature have not been carried out so far. Predicting the magnitude and impact of cyanobacterial blooms in the future as a response to global warming requires an understanding of how cyanobacteria might change in the long term due to climate change. 2. Here we examined the effect of exposing three Microcystis aeruginosa strains isolated in Romania to ambient (22°C) and high (26°C) temperature for 6 months. Then, the competitive ability of the strains after heat acclimation was evaluated, by analysing their impact on plankton community composition. 3. One of the three strains displayed significantly higher growth rates after 6 months of cultivation at higher temperatures. Following inoculation into a natural plankton community, the overall cyanobacterial abundance significantly increased in the cultures inoculated with this heat-acclimated strain of M. aeruginosa as compared to the ambient-acclimated version. The structure of eukaryotic communities was impacted by both inoculated cyanobacteria and temperature during the experiments. 4. The results of this study emphasise the high potential of cyanobacteria to respond to stressors, and highlight the fact that previous acclimation to warming is a critical factor in shaping the overall structure of plankton communities. 5. Our study strongly advocates for including a step of culture acclimation to future experimental conditions in research programmes aiming to better understand the long-term impact of climate change on aquatic ecosystems

Fire intensity regulates the short-term postfire response of the microbiome in Arctic tundra soil

Arctic tundra fires have been increasing in extent, frequency and intensity and are likely impacting both soil nitrogen (N) and phosphorus (P) cycling and, thus, permafrost ecosystem functioning. However, little is known on the underlying microbial mechanisms, and different fire intensities were neglected so far. To better understand immediate influences of different fire intensities on the soil microbiome involved in nutrient cycling in permafrost-affected soil, we deployed experimental fires with low and high intensity on an Arctic tundra soil on Disko Island, Greenland. Soil sampling took place three days postfire and included an unburned control. Using quantitative real-time PCR, copy numbers of 16S and ITS as well as of 17 genes coding for functional microbial groups catalyzing major steps of N and P turnover were assessed. We show that fires change the abundance of microbial groups already after three days with fire intensity as key mediating factor. Specifically, low-intensity fire significantly enhanced the abundance of chiA mineralizers and ammonia-oxidizing archaea, while other groups were not affected. On the contrary, high-intensity fire decreased the abundance of chiA mineralizers and of microbes that fix dinitrogen, indicating a dampening effect on N cycling. Only high-intensity fires enhanced ammonium concentrations (by an order of magnitude). This can be explained by burned plant material and the absence of plant uptake, together with impaired further N processing. Fire with high intensity also decreased nirK-type denitrifiers. In contrast, after fire with low intensity there was a trend for a decreased nosZ : (nirK+nirS) ratio, indicating – together with increased nitrate concentrations – an enhanced potential for nitric oxide and nitrous oxide emissions. Concerning P transformation, only gcd was affected in the short term which is important for P solubilization. Changes in gene numbers consistently showed the same contrasting pattern of elevated abundance with low fire intensity and decreased abundance with high fire intensity. Differentiating fire intensities is therefore crucial for further, longer-term studies of fire-induced changes in N and P transformations and potential nutrient-climate feedbacks of permafrost-affected soils

A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils—changing the paradigm

The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (C) and total N concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought. Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously

Att "smälta" in i vuxenlivet : övergången från ungdom till vuxen

For today's young adults, the experience of being in the age period 18-30 years is, compared with previous generations, quite different. There is more room for exploring and experimenting when lifestyles and life-choices are no longer predetermined, and most things are possible for today's young people. The object of this thesis is to examine young people\2019s experiences in the transition from youth to adulthood and to illuminate those experiences and difficulties that take place during this period. In the study, qualitative interviews were used in four focus groups, divided up in two age categories. The results reveal that the feeling of being an adult arises in the latter part of the period, and that variations between individuals are readily apparent. Creating new and changing old roles, and in particular the adoption of occupational and family roles, are most noticeable during this period. This means that the period in many cases is experienced as confusing and stressful, as responsibility must be taken for the multitude of choices, and change that are made

Examining the support–supply and bud‐packing hypotheses for the increase in toothed leaf margins in northern deciduous floras

Premise The proportion of woody dicots with toothed leaves increases toward colder regions, a relationship used to reconstruct past mean annual temperatures. Recent hypotheses explaining this relationship are that (1) leaves in colder regions are thinner, requiring thick veins for support and water supply, with the resulting craspedodromous venation leading to marginal teeth (support–supply hypothesis) or that (2) teeth are associated with the packing of leaf primordia in winter buds (bud‐packing hypothesis). Methods We addressed these hypotheses by examining leaf thickness, number of primordia in buds, growing season length (mean annual temperature, MAT), and other traits in 151 deciduous woody species using georeferenced occurrences and a Bayesian model controlling for phylogeny. We excluded evergreen species because longer leaf life spans correlate with higher leaf mass per area, precluding the detection of independent effects of leaf thickness on leaf‐margin type. Results The best model predicted toothed leaves with 94% accuracy, with growing season length the strongest predictor. Neither leaf thickness nor number of leaves preformed in buds significantly influenced margin type, rejecting the support–supply and bud‐packing hypotheses. Conclusions A direct selective benefit of leaf teeth via a carbon gain early in the spring as proposed by Royer and Wilf (2006) would match the strong correlation between toothed species occurrence and short growing season found here using Bayesian hierarchical models. Efforts should be directed to physiological work quantifying seasonal photosynthate production in toothed and nontoothed leaves.ISSN:1914-2016:ISSN:0002-912

Fire intensity regulates the short-term postfire response of the microbiome in Arctic tundra soil

Arctic tundra fires have been increasing in extent, frequency and intensity and are likely impacting both soil nitrogen (N) and phosphorus (P) cycling and, thus, permafrost ecosystem functioning. However, little is known on the underlying microbial mechanisms, and different fire intensities were neglected so far. To better understand immediate influences of different fire intensities on the soil microbiome involved in nutrient cycling in permafrost-affected soil, we deployed experimental fires with low and high intensity on an Arctic tundra soil on Disko Island, Greenland. Soil sampling took place three days postfire and included an unburned control. Using quantitative real-time PCR, copy numbers of 16S and ITS as well as of 17 genes coding for functional microbial groups catalyzing major steps of N and P turnover were assessed.We show that fires change the abundance of microbial groups already after three days with fire intensity as key mediating factor. Specifically, low-intensity fire significantly enhanced the abundance of chiA mineralizers and ammonia-oxidizing archaea, while other groups were not affected. On the contrary, high-intensity fire decreased the abundance of chiA mineralizers and of microbes that fix dinitrogen, indicating a dampening effect on N cycling. Only high-intensity fires enhanced ammonium concentrations (by an order of magnitude). This can be explained by burned plant material and the absence of plant uptake, together with impaired further N processing. Fire with high intensity also decreased nirK-type denitrifiers. In contrast, after fire with low intensity there was a trend for a decreased nosZ : (nirK+nirS) ratio, indicating – together with increased nitrate concentrations – an enhanced potential for nitric oxide and nitrous oxide emissions. Concerning P transformation, only gcd was affected in the short term which is important for P solubilization.Changes in gene numbers consistently showed the same contrasting pattern of elevated abundance with low fire intensity and decreased abundance with high fire intensity. Differentiating fire intensities is therefore crucial for further, longer-term studies of fire-induced changes in N and P transformations and potential nutrient-climate feedbacks of permafrost-affected soils

Magnetic Biofilm Carriers: The Use of Novel Magnetic Foam Glass Particles in Anaerobic Digestion of Sugar Beet Silage

The use of recently developed magnetic foam glass particles for immobilization of microbial biomass was tested. The effect of the particles was illustrated at the production of biogas from sugar beet silage as the sole substrate. Lab-scale fermentation experiments were conducted using a mesophilic completely stirred tank reactor and a magnetic separator. Microscopic analysis revealed biofilm coverage of 50–60% on the surface of the particles within 110 days. It was possible to recover 76.3% of the particles from fermentation effluent by means of a separation procedure based on magnetic forces. Comparing a particle charged reactor with a control reactor showed a small performance gain. The methane rate was increased from 1.18±0.09 to 1.25±0.06 L L−1 d−1 and the methane yield was increased from 0.302±0.029 to 0.318±0.022 L g−1 (volatile solids) at an organic loading rate of 3.93±0.22 g L−1 d−1 (volatile solids). Maximum methane rates of 1.42 L L−1 d−1 at an organic loading rate of 4.60 g (volatile solids) L−1 d−1 (reactor including magnetic particles) and 1.34 L L−1 d−1 at 3.73 g L−1 d−1 (control reactor) were achieved. Based on the results, it can be concluded that the use of magnetic particles could be an attractive option for the optimization of biogas production

Degradation Kinetics of Lignocellulolytic Enzymes in a Biogas Reactor Using Quantitative Mass Spectrometry

The supplementation of lignocellulose-degrading enzymes can be used to enhance the performance of biogas production in industrial biogas plants. Since the structural stability of these enzyme preparations is essential for efficient application, reliable methods for the assessment of enzyme stability are crucial. Here, a mass-spectrometric-based assay was established to monitor the structural stability of enzymes, i.e., the structural integrity of these proteins, in anaerobic digestion (AD). The analysis of extracts of Lentinula edodes revealed the rapid degradation of lignocellulose-degrading enzymes, with an approximate half-life of 1.5 h. The observed low structural stability of lignocellulose-degrading enzymes in AD corresponded with previous results obtained for biogas content. The established workflow can be easily adapted for the monitoring of other enzyme formulations and provides a platform for evaluating the effects of enzyme additions in AD, together with a characterization of the biochemical methane potential used in order to determine the biodegradability of organic substrates.BMELPeer Reviewe

A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils : changing the paradigm

The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (C) and total N concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought. Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously.peerReviewe

Zebrafish models for nemaline myopathy reveal a spectrum of nemaline bodies contributing to reduced muscle function

Nemaline myopathy is characterized by muscle weakness and the presence of rod-like (nemaline) bodies. The genetic etiology of nemaline myopathy is becoming increasingly understood with mutations in ten genes now known to cause the disease. Despite this, the mechanism by which skeletal muscle weakness occurs remains elusive, with previous studies showing no correlation between the frequency of nemaline bodies and disease severity. To investigate the formation of nemaline bodies and their role in pathogenesis, we generated overexpression and loss-of-function zebrafish models for skeletal muscle α-actin (ACTA1) and nebulin (NEB). We identify three distinct types of nemaline bodies and visualize their formation in vivo, demonstrating these nemaline bodies not only exhibit different subcellular origins, but also have distinct pathological consequences within the skeletal muscle. One subtype is highly dynamic and upon breakdown leads to the accumulation of cytoplasmic actin contributing to muscle weakness. Examination of a Neb-deficient model suggests this mechanism may be common in nemaline myopathy. Another subtype results from a reduction of actin and forms a more stable cytoplasmic body. In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization. Analysis of zebrafish and muscle biopsies from ACTA1 nemaline myopathy patients demonstrates that nemaline bodies also possess a different protein signature. In addition, we show that the ACTA1 mutation causes impaired actin incorporation and localization in the sarcomere. Together these data provide a novel examination of nemaline body origins and dynamics in vivo and identifies pathological changes that correlate with muscle weakness