Biogenic volatile organic compound emissions in four vegetation types in high arctic Greenland

Biogenic volatile organic compounds (BVOCs) emitted from terrestrial vegetation participate in oxidative reactions in the atmosphere, leading to the formation of secondary organic aerosols and longer lifetime of methane. Global models of BVOC emissions have assumed minimal emissions from the high latitudes. However, measurements from this region are lacking, and studies from the high arctic are yet to be published. This study aimed to obtain estimates for BVOC emissions from the high arctic, and hereby to add new knowledge to the understanding of global BVOC emissions. Measurements were conducted in four vegetation types dominated by Cassiope tetragona, Salix arctica, Vaccinium uliginosum and a mixture of Kobresia myosuroides, Dryas spp. and Poa arctica. Emissions were measured by an enclosure technique and collection of volatiles into adsorbent cartridges in August. Volatiles were analyzed by gas chromatography–mass spectrometry following thermal desorption. Isoprene showed highest emissions in S. arctica heath. Monoterpene and sesquiterpene emissions were especially associated with C. tetragona heath. Total observed emissions were comparable in magnitude to emissions previously found in the subarctic, whereas isoprene emissions were lower. This study shows that considerable amounts of BVOCs are emitted from the high arctic. The results are also of importance as the emissions from this region are expected to increase in the future as a result of the predicted climate warming in the high arctic. We suggest further studies to assess the effects of climate changes in the region in order to gain new knowledge and understanding of future global BVOC emissions.     

The shift in plant species composition in a subarctic mountain birch forest floor due to climate change would modify the biogenic volatile organic compound emission profile

Background and aims

Mountain birch forests dominate in the Subarctic but little is known of their non-methane biogenic volatile organic compound (BVOC) emissions. The dwarf shrubs Empetrum hermaphroditum, Vaccinium myrtillus and Vaccinium uliginosum co-dominate in the forest floors of these forests. The abundance of these three dwarf shrubs relative to each other could be affected by climate warming expected to increase nutrient availability by accelerating litter decomposition and nutrient mineralization. We 1) compared the BVOC emission profiles of vegetation covers dominated by E. hermaphroditum and V. myrtillus plus V. uliginosum in a subarctic mountain birch forest floor, 2) distinguished the BVOCs emitted from plants and soil and 3) measured how the BVOC emissions from the different vegetation covers differed under darkness.

Methods

BVOCs were sampled during two growing seasons using a conventional ecosystem chamber-based method, collected on adsorbent and analyzed with gas chromatography–mass spectrometry.

Results

High abundance of E. hermaphroditum increased the sesquiterpene emissions. Soil released fewer different BVOCs than controls (i.e. natural vegetation) but the total emission rates were similar. Darkness did not affect the emissions. Carbon emitted as BVOCs was less than 0.2% of the CO₂ exchange.

Conclusions

Our results suggest that sesquiterpene emissions from subarctic mountain birch forest floors would be reduced following an increased abundance of V. myrtillus and V. uliginosum with climate change because these species respond rapidly to increased nutrient availability.     

Observational study to characterise 24-hour COPD symptoms and their relationship with patient-reported outcomes: results from the ASSESS study

Background

Few studies have investigated the 24-hour symptom profile in patients with COPD or how symptoms during the 24-hour day are inter-related. This observational study assessed the prevalence, severity and relationship between night-time, early morning and daytime COPD symptoms and explored the relationship between 24-hour symptoms and other patient-reported outcomes.

Methods

The study enrolled patients with stable COPD in clinical practice. Baseline night-time, early morning and daytime symptoms (symptom questionnaire), severity of airflow obstruction (FEV₁), dyspnoea (modified Medical Research Council Dyspnoea Scale), health status (COPD Assessment Test), anxiety and depression levels (Hospital Anxiety and Depression Scale), sleep quality (COPD and Asthma Sleep Impact Scale) and physical activity level (sedentary, moderately active or active) were recorded.

Results

The full analysis set included 727 patients: 65.8% male, mean ± standard deviation age 67.2 ± 8.8 years, % predicted FEV₁ 52.8 ± 20.5%.In each part of the 24-hour day, >60% of patients reported experiencing ≥1 symptom in the week before baseline. Symptoms were more common in the early morning and daytime versus night-time (81.4%, 82.7% and 63.0%, respectively). Symptom severity was comparable for each period assessed. Overall, in the week before baseline, 56.7% of patients had symptoms throughout the whole 24-hour day (3 parts of the day); 79.9% had symptoms in ≥2 parts of the 24-hour day. Symptoms during each part of the day were inter-related, irrespective of disease severity (all p < 0.001).Early morning and daytime symptoms were associated with the severity of airflow obstruction (p < 0.05 for both). Night-time, early morning and daytime symptoms were all associated with worse dyspnoea, health status and sleep quality, and higher anxiety and depression levels (all p < 0.001 versus patients without symptoms in each corresponding period). In each part of the 24-hour day, there was also an association between symptoms and a patient’s physical activity level (p < 0.05 for each period).

Conclusions

More than half of patients experienced COPD symptoms throughout the whole 24-hour day. There was a significant relationship between night-time, early morning and daytime symptoms. In each period, symptoms were associated with worse patient-reported outcomes, suggesting that improving 24-hour symptoms should be an important consideration in the management of COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0122-1) contains supplementary material, which is available to authorized users.     

Influence of increased nutrient availability on biogenic volatile organic compound (BVOC) emissions and leaf anatomy of subarctic dwarf shrubs under climate warming and increased cloudiness

Background and AimsClimate change is subjecting subarctic ecosystems to elevated temperature, increased nutrient availability and reduced light availability (due to increasing cloud cover). This may affect subarctic vegetation by altering the emissions of biogenic volatile organic compounds (BVOCs) and leaf anatomy. We investigated the effects of increased nutrient availability on BVOC emissions and leaf anatomy of three subarctic dwarf shrub species, Empetrum hermaphroditum, Cassiope tetragona and Betula nana, and if increased nutrient availability modifies the responses to warming and shading.MethodsMeasurements of BVOCs were performed in situ in long-term field experiments in the Subarctic using a dynamic enclosure system and collection of BVOCs into adsorbent cartridges analysed by gas chromatography–mass spectrometry. Leaf anatomy was studied using light microscopy and scanning electron microscopy.Key ResultsIncreased nutrient availability increased monoterpene emission rates and altered the emission profile of B. nana, and increased sesquiterpene and oxygenated monoterpene emissions of C. tetragona. Increased nutrient availability increased leaf tissue thicknesses of B. nana and C. tetragona, while it caused thinner epidermis and the highest fraction of functional (intact) glandular trichomes for E. hermaphroditum. Increased nutrient availability and warming synergistically increased mesophyll intercellular space of B. nana and glandular trichome density of C. tetragona, while treatments combining increased nutrient availability and shading had an opposite effect in C. tetragona.ConclusionsIncreased nutrient availability may enhance the protection capacity against biotic and abiotic stresses (especially heat and drought) in subarctic shrubs under future warming conditions as opposed to increased cloudiness, which could lead to decreased resistance. The study emphasizes the importance of changes in nutrient availability in the Subarctic, which can interact with climate warming and increased cloudiness effects.     

Few long-term effects of simulated climate change on volatile organic compound emissions and leaf chemistry of three subarctic dwarf shrubs

Climate change is exposing arctic ecosystems to higher temperature, increased nutrient availability and shading due to the increasing cloud cover and the expanding forests. In this work, we assessed how these factors affect the emissions of biogenic volatile organic compounds (BVOCs) from three subarctic dwarf shrub species in a field experiment after 18 treatment years. Of the studied species the willow Salix phylicifolia L. was the only isoprene-emitter with an emission potential of 16.1 ± 8.4 μg g⁻¹ dw h⁻¹ (at 30 °C and photosynthetic photon flux density of 1000 μmol m⁻² s⁻¹). The dwarf birch Betula nana L. had significant emissions of various reactive BVOCs, including monoterpenes and sesquiterpenes. The evergreen Cassiope tetragona (L.) D. Don emitted high amounts of mono- and sesquiterpenes. Due to chance, the temperature in the warming treatment (employing open-top plastic tents) and the unwarmed treatments was similar at the time of the measurements, and therefore long-term indirect effects of warming could be assessed without interference of temperature differences at the time of measurement. The long-term warming had not altered foliar N, P or condensed tannin concentrations, but it had led to other chemical changes detected in the near-infrared reflectance spectra of the leaves. Nevertheless, there were no significant differences in the BVOC emissions per unit leaf mass measured by the dynamic enclosure method and gas chromatography-mass spectrometry. Annual additions of NPK fertilizer, which mimicked increased nutrient availability, had accumulated P in the leaves of all species. In addition, fertilization marginally increased the leaf N concentration of B. nana. The only significant fertilization effect on BVOC emissions was a stimulation of emission of the sesquiterpene β-selinene from S. phylicifolia. The shading treatment obtained by dome-shaped hessian tents did not cause clear long-term changes in leaf chemistry or BVOC emissions. The only observed change was a marginally significant increase in sesquiterpene emissions from B. nana. When the treatment effects on long-term biomass changes in the different treatments were taken into account by proportioning the BVOC emissions to the biomass of each species in the field treatments, warming led to a significant increase and shading to a decrease in the total BVOC emissions per unit ground area from B. nana. These results highlight the importance of an integrated approach for realistic assessment of responses to climate change.     

Non-Methane Biogenic Volatile Organic Compound Emissions from a Subarctic Peatland Under Enhanced UV-B Radiation

Boreal and subarctic peatlands have been extensively studied for their major role in the global carbon balance. However, study efforts have so far neglected the contribution of these ecosystems to the non-methane biogenic volatile organic compound (BVOC) emissions, which are important in the atmospheric chemistry and feedbacks on climate change. We aimed at estimating the BVOC emissions from a subarctic peatland in northern Finland. Furthermore, our aim was to assess how these emissions are affected by enhanced UV-B radiation, the amount of which has increased especially at high latitudes as a result of stratospheric ozone depletion. The contribution of BVOC emissions to the total net carbon exchange and correlations between the emission of different BVOCs and net ecosystem CO₂ exchange, CH₄ emission, total green leaf area, and abiotic factors were also studied. The UV-B exposure, simulating a 20% depletion of stratospheric ozone, was started in 2003, and measurements were performed during the growing seasons of 2006 and 2008. The subarctic peatland proved to be a small source of BVOCs and the dominant moss, Warnstorfia exannulata, emitted a diverse compound spectrum. The water table level exerted a major influence on the BVOC emissions surpassing the effect of enhanced UV-B. In fact, no overall UV-B effect was established on the BVOC emissions, apart from toluene and 1-octene, emissions of which were doubled and tripled by enhanced UV-B in 2008, respectively. The contribution of BVOCs to the total net carbon exchange was below 1%.     

Physiological and isotopic aspects of photosynthesis in peperomia

Physiological and isotopic aspects of several Peperomia species were investigated. All but one species had C₃-like stomatal behavior, in that stomata were open during the day and closed during the night. In these species, most atmospheric CO₂ uptake occurred during the day. Concurrent with this stomatal behavior, there were Crassulacean acid metabolism-like acid fluctuations in most species. Carbon and hydrogen isotope ratios of cellulose nitrate from Peperomia reflect their physiological behavior. The δ¹³C values of cellulose nitrate from Peperomia species were similar to values observed in C₃ plants and consistent with the daytime uptake of exogeneous CO₂ via the C₃ photosynthetic pathway. The δD values of cellulose nitrate from Peperomia species approach those of Crassulacean acid metabolism plants. These elevated δD values are caused by fractionations occurring during biochemical reactions and not as a consequence of water relations.     

Diversity and Structure of Bacterial Communities in Arctic versus Antarctic Pack Ice

A comprehensive assessment of bacterial diversity and community composition in arctic and antarctic pack ice was conducted through cultivation and cultivation-independent molecular techniques. We sequenced 16S rRNA genes from 115 and 87 pure cultures of bacteria isolated from arctic and antarctic pack ice, respectively. Most of the 33 arctic phylotypes were >97% identical to previously described antarctic species or to our own antarctic isolates. At both poles, the α- and γ-proteobacteria and the Cytophaga-Flavobacterium group were the dominant taxonomic bacterial groups identified by cultivation as well as by molecular methods. The analysis of 16S rRNA gene clone libraries from multiple arctic and antarctic pack ice samples revealed a high incidence of closely overlapping 16S rRNA gene clone and isolate sequences. Simultaneous analysis of environmental samples with fluorescence in situ hybridization (FISH) showed that ~95% of 4′,6′-diamidino-2-phenylindole (DAPI)-stained cells hybridized with the general bacterial probe EUB338. More than 90% of those were further assignable. Approximately 50 and 36% were identified as γ-proteobacteria in arctic and antarctic samples,respectively. Approximately 25% were identified as α-proteobacteria, and 25% were identified as belonging to the Cytophaga-Flavobacterium group. For the quantification of specific members of the sea ice community, new oligonucleotide probes were developed which target the genera Octadecabacter, Glaciecola, Psychrobacter, Marinobacter, Shewanella, and Polaribacter. High FISH detection rates of these groups as well as high viable counts corroborated the overlap of clone and isolate sequences. A terrestrial influence on the arctic pack ice community was suggested by the presence of limnic phylotypes.     

Catabolism of [1-C]levulinic Acid by etiolated and greening barley leaves

Levulinic acid (LA), a competitive inhibitor of δ-aminolevulinic acid (ALA) dehydratase (EC 4.2.1.24), has been used extensively in the study of ALA formation during greening. When [1-¹⁴C]LA is administered to etiolated barley (Hordeum vulgare L. var. Larker) shoots in darkness, ¹⁴CO₂ is evolved. This process is accelerated when such tissues are incubated with 2 millimolar ALA or placed under continuous illumination. Label from the C-1 of LA becomes incorporated into organic acids, amino acids, sugars, lipids, and proteins during a 4-hour incubation in darkness or in the light. This metabolism is discussed in relation to the use of LA as a tool in the study of chlorophyll synthesis in higher plants.     

Climate change alters leaf anatomy,but has no effects on volatile emissions from arctic plants

Biogenic volatile organic compound (BVOC) emissions are expected to change substantially because of the rapid advancement of climate change in the Arctic. BVOC emission changes can feed back both positively and negatively on climate warming. We investigated the effects of elevated temperature and shading on BVOC emissions from arctic plant species Empetrum hermaphroditum, Cassiope tetragona, Betula nana and Salix arctica. Measurements were performed in situ in long‐term field experiments in subarctic and high Arctic using a dynamic enclosure system and collection of BVOCs into adsorbent cartridges analysed by gas chromatography‐mass spectrometry. In order to assess whether the treatments had resulted in anatomical adaptations, we additionally examined leaf anatomy using light microscopy and scanning electron microscopy. Against expectations based on the known temperature and light‐dependency of BVOC emissions, the emissions were barely affected by the treatments. In contrast, leaf anatomy of the studied plants was significantly altered in response to the treatments, and these responses appear to differ from species found at lower latitudes. We suggest that leaf anatomical acclimation may partially explain the lacking treatment effects on BVOC emissions at plant shoot‐level. However, more studies are needed to unravel why BVOC emission responses in arctic plants differ from temperate species.     

Changes in Bacterial Populations and in Biphenyl Dioxygenase Gene Diversity in a Polychlorinated Biphenyl-Polluted Soil after Introduction of Willow Trees for Rhizoremediation

The aim of this study was to analyze the structural and functional changes occurring in a polychlorinated-biphenyl (PCB)-contaminated soil ecosystem after the introduction of a suitable host plant for rhizoremediation (Salix viminalis). We have studied the populations and phylogenetic distribution of key bacterial groups (Alpha- and Betaproteobacteria, Acidobacteria, and Actinobacteria) and the genes encoding iron-sulfur protein α (ISPα) subunits of the toluene/biphenyl dioxygenases in soil and rhizosphere by screening gene libraries using temperature gradient gel electrophoresis. The results, based on the analysis of 415 clones grouped into 133 operational taxonomic units that were sequence analyzed (>128 kbp), show that the rhizospheric bacterial community which evolved from the native soil community during the development of the root system was distinct from the soil community for all groups studied except for the Actinobacteria. Proteobacteria were enriched in the rhizosphere and dominated both in rhizosphere and soil. There was a higher than expected abundance of Betaproteobacteria in the native and in the planted PCB-polluted soil. The ISPα sequences retrieved indicate a high degree of catabolic and phylogenetic diversity. Many sequences clustered with biphenyl dioxygenase sequences from gram-negative bacteria. A distinct cluster that was composed of sequences from this study, some previously described environmental sequences, and a putative ISPα from Sphingomonas wittichii RW1 seems to contain greater diversity than the presently recognized toluene/biphenyl dioxygenase subfamily. Moreover, the rhizosphere selected for two ISPα sequences that accounted for almost 60% of the gene library and were very similar to sequences harbored by Pseudomonas species.     

Influence of light and temperature on monoterpene emission rates from slash pine

There is a growing awareness of vegetation's role as a source of potentially reactive hydrocarbons that may serve as photochemical oxidant precursors. This study assessed the influence of light and temperature, independently, on monoterpene emissions from slash pine (Pinus elliottii Engelm.). Plants were preconditioned in a growth chamber, then transferred to an environmentally controlled gas exchange chamber. Samples of the chamber atmosphere were collected; the monoterpenes were concentrated cryogenically and measured by gas chromatography. Five monoterpenes (α-pinene, β-pinene, myrcene, limonene, and β-phellandrene) were present in the vapor phase surrounding the plants in sufficient quantity for reliable measurement. Light did not directly influence monoterpene emission rates since the emissions were similar in both the dark and at various light intensities. Monoterpene emission rates increased exponentially with temperature (i. e. emissions depend on temperature in a log-linear manner). The summed emissions of the five monoterpenes ranged from 3 to 21 micrograms C per gram dry weight per hour as temperature was increased from 20 to 46 C. Initially, emission rates from heat-stressed needles were similar to healthy needles, but rates decreased 11% per day. Daily carbon loss through monoterpene emissions accounted for approximately 0.4% of the carbon fixed during photosynthesis.     

Quantifying Recent Ecological Changes in Remote Lakes of North America and Greenland Using Sediment Diatom Assemblages

Background

Although arctic lakes have responded sensitively to 20^th-century climate change, it remains uncertain how these ecological transformations compare with alpine and montane-boreal counterparts over the same interval. Furthermore, it is unclear to what degree other forcings, including atmospheric deposition of anthropogenic reactive nitrogen (Nr), have participated in recent regime shifts. Diatom-based paleolimnological syntheses offer an effective tool for retrospective assessments of past and ongoing changes in remote lake ecosystems.

Methodology/Principal Findings

We synthesized 52 dated sediment diatom records from lakes in western North America and west Greenland, spanning broad latitudinal and altitudinal gradients, and representing alpine (n = 15), arctic (n = 20), and forested boreal-montane (n = 17) ecosystems. Diatom compositional turnover (β-diversity) during the 20^th century was estimated using Detrended Canonical Correspondence Analysis (DCCA) for each site and compared, for cores with sufficiently robust chronologies, to both the 19^th century and the prior ∼250 years (Little Ice Age). For both arctic and alpine lakes, β-diversity during the 20^th century is significantly greater than the previous 350 years, and increases with both latitude and altitude. Because no correlation is apparent between 20^th-century diatom β-diversity and any single physical or limnological parameter (including lake and catchment area, maximum depth, pH, conductivity, [NO₃ ⁻], modeled Nr deposition, ambient summer and winter air temperatures, and modeled temperature trends 1948–2008), we used Principal Components Analysis (PCA) to summarize the amplitude of recent changes in relationship to lake pH, lake:catchment area ratio, modeled Nr deposition, and recent temperature trends.

Conclusions/Significance

The ecological responses of remote lakes to post-industrial environmental changes are complex. However, two regions reveal concentrations of sites with elevated 20^th-century diatom β-diversity: the Arctic where temperatures are increasing most rapidly, and mid-latitude alpine lakes impacted by high Nr deposition rates. We predict that remote lakes will continue to shift towards new ecological states in the Anthropocene, particularly in regions where these two forcings begin to intersect geographically.     

Identification and quantitative analysis of the volatile substances emitted by maturing cotton in the field

When atmosphere from cotton plants (Gossypium hirsutum L., var. Deltapine Smoothleaf) was condensed by passing it over the expansion coil of an air conditioner and three 1-hour collections per day (early morning, noon, and late afternoon) were made, the total essential oils were found to consist of 50 to 60% β-bisabolol (I_k 1660) and γ-bisabolene (I_k 1550) and 30 to 40% geraniol (I_k 1250), myrtenal (I_k 1328), nerolidol (I_k 1520), and β-caryophyllene oxide (I_k 1590). As the plant matured, trans-2-hexanol was produced in concentrations of 7 to 27%. Before fruiting, β-bisabolol made up as much as 60% of the total essential oil transpired by the plants, and as the concentration of β-bisabolol increased, that of γ-bisabolene decreased.     

Climate change‐induced vegetation change as a driver of increased subarctic biogenic volatile organic compound emissions

Emissions of biogenic volatile organic compounds (BVOCs) have been earlier shown to be highly temperature sensitive in subarctic ecosystems. As these ecosystems experience rapidly advancing pronounced climate warming, we aimed to investigate how warming affects the BVOC emissions in the long term (up to 13 treatment years). We also aimed to assess whether the increased litterfall resulting from the vegetation changes in the warming subarctic would affect the emissions. The study was conducted in a field experiment with factorial open‐top chamber warming and annual litter addition treatments on subarctic heath in Abisko, northern Sweden. After 11 and 13 treatment years, BVOCs were sampled from plant communities in the experimental plots using a push–pull enclosure technique and collection into adsorbent cartridges during the growing season and analyzed with gas chromatography–mass spectrometry. Plant species coverage in the plots was analyzed by the point intercept method. Warming by 2 °C caused a 2‐fold increase in monoterpene and 5‐fold increase in sesquiterpene emissions, averaged over all measurements. When the momentary effect of temperature was diminished by standardization of emissions to a fixed temperature, warming still had a significant effect suggesting that emissions were also indirectly increased. This indirect increase appeared to result from increased plant coverage and changes in vegetation composition. The litter addition treatment also caused significant increases in the emission rates of some BVOC groups, especially when combined with warming. The combined treatment had both the largest vegetation changes and the highest BVOC emissions. The increased emissions under litter addition were probably a result of a changed vegetation composition due to alleviated nutrient limitation and stimulated microbial production of BVOCs. We suggest that the changes in the subarctic vegetation composition induced by climate warming will be the major factor indirectly affecting the BVOC emission potentials and composition.     

Synapsis and strand exchange in the resolution and DNA inversion reactions catalysed by the beta recombinase

In the presence of a sequence-independent chromatin-associated protein, such as Hbsu or HMGB, the β recombinase catalyses resolution between two directly oriented recombination sites (six sites) and both resolution and DNA inversion between two inversely oriented six sites. Assembly of the synaptic complex requires binding of the β recombinase to the six sites and the presence of Hbsu. Whether resolution or inversion will take place depends on the relative orientation of the two six sites, the level of DNA supercoiling and the amounts of Hbsu. In this work, the topologies of the products of the resolution and inversion reactions were analysed. The resolution reaction generated mainly singly catenated DNA circles, while DNA inversion gave rise to unknotted circles and small amounts of DNA molecules containing 3- or 5-noded knots. In spite of the distinctive features of the β system, the topology of synapsis and strand exchange during the resolution reaction is similar to that of Tn3 and γδ resolvases. The ability of the β recombinase to catalyse both inversion and resolution reactions probably reflects different possible architectures of the synaptic complex, which to a large extent depends on Hbsu.     

Phenotypic selection on floral traits in the arctic plant Parrya nudicaulis (Brassicaceae)

The evolution of floral traits is often attributed to pollinator‐mediated selection; however, the importance of pollinators as selective agents in arctic environments is poorly resolved. In arctic and subarctic regions that are thought to be pollen limited, selection is expected to either favor floral traits that increase pollinator attraction or promote reproductive assurance through selfing. We quantified phenotypic selection on floral traits in two arctic and two subarctic populations of the self‐compatible, but largely pollinator‐dependent, Parrya nudicaulis. Additionally, we measured selection in plants in both open pollination and pollen augmentation treatments to estimate selection imposed by pollinators in one population. Seed production was found to be limited by pollen availability and strong directional selection on flower number was observed. We did not detect consistently greater magnitudes of selection on floral traits in the arctic relative to the subarctic populations. Directional selection for more pigmented flowers in one arctic population was observed, however. In some populations, selection on flower color was found to interact with other traits. We did not detect consistently stronger selection gradients across all traits for plants exposed to pollinator selection relative to those in the pollen augmentation treatment; however, directional selection tended to be higher for some floral traits in open‐pollinated plants.     

Flavobacterium sp. Strain 4221 and Pedobacter sp. Strain 4236 β-1,3-Glucanases That Are Active at Low Temperatures

Secretion of β-1,3-glucanases by the arctic bacterial isolates 4221 and 4236, related to the genera Flavobacterium and Pedobacter, was discovered. Escherichia coli and Lactococcus lactis expression of β-1,3-glucanases Glc4221-1 and Glc4236-1 from the respective isolates was achieved. The enzymes hydrolyzed fungal cell walls and retained activity at low temperatures.     

Diversity of active aerobic methanotrophs along depth profiles of arctic and subarctic lake water column and sediments

Methane (CH₄) emitted from high-latitude lakes accounts for 2–6% of the global atmospheric CH₄ budget. Methanotrophs in lake sediments and water columns mitigate the amount of CH₄ that enters the atmosphere, yet their identity and activity in arctic and subarctic lakes are poorly understood. We used stable isotope probing (SIP), quantitative PCR (Q-PCR), pyrosequencing and enrichment cultures to determine the identity and diversity of active aerobic methanotrophs in the water columns and sediments (0–25 cm) from an arctic tundra lake (Lake Qalluuraq) on the north slope of Alaska and a subarctic taiga lake (Lake Killarney) in Alaska''s interior. The water column CH₄ oxidation potential for these shallow (∼2 m deep) lakes was greatest in hypoxic bottom water from the subarctic lake. The type II methanotroph, Methylocystis, was prevalent in enrichment cultures of planktonic methanotrophs from the water columns. In the sediments, type I methanotrophs (Methylobacter, Methylosoma and Methylomonas) at the sediment-water interface (0–1 cm) were most active in assimilating CH₄, whereas the type I methanotroph Methylobacter and/or type II methanotroph Methylocystis contributed substantially to carbon acquisition in the deeper (15–20 cm) sediments. In addition to methanotrophs, an unexpectedly high abundance of methylotrophs also actively utilized CH₄-derived carbon. This study provides new insight into the identity and activity of methanotrophs in the sediments and water from high-latitude lakes.     

Relationships between the Circadian System and Alzheimer's Disease-Like Symptoms in Drosophila

Circadian clocks coordinate physiological, neurological, and behavioral functions into circa 24 hour rhythms, and the molecular mechanisms underlying circadian clock oscillations are conserved from Drosophila to humans. Clock oscillations and clock-controlled rhythms are known to dampen during aging; additionally, genetic or environmental clock disruption leads to accelerated aging and increased susceptibility to age-related pathologies. Neurodegenerative diseases, such as Alzheimer''s disease (AD), are associated with a decay of circadian rhythms, but it is not clear whether circadian disruption accelerates neuronal and motor decline associated with these diseases. To address this question, we utilized transgenic Drosophila expressing various Amyloid-β (Aβ) peptides, which are prone to form aggregates characteristic of AD pathology in humans. We compared development of AD-like symptoms in adult flies expressing Aβ peptides in the wild type background and in flies with clocks disrupted via a null mutation in the clock gene period (per⁰¹). No significant differences were observed in longevity, climbing ability and brain neurodegeneration levels between control and clock-deficient flies, suggesting that loss of clock function does not exacerbate pathogenicity caused by human-derived Aβ peptides in flies. However, AD-like pathologies affected the circadian system in aging flies. We report that rest/activity rhythms were impaired in an age-dependent manner. Flies expressing the highly pathogenic arctic Aβ peptide showed a dramatic degradation of these rhythms in tune with their reduced longevity and impaired climbing ability. At the same time, the central pacemaker remained intact in these flies providing evidence that expression of Aβ peptides causes rhythm degradation downstream from the central clock mechanism.