Climate change alters temporal dynamics of alpine soil microbial functioning and biogeochemical cycling via earlier snowmelt

Soil microbial communities regulate global biogeochemical cycles and respond rapidly to changing environmental conditions. However, understanding how soil microbial communities respond to climate change, and how this influences biogeochemical cycles, remains a major challenge. This is especially pertinent in alpine regions where climate change is taking place at double the rate of the global average, with large reductions in snow cover and earlier spring snowmelt expected as a consequence. Here, we show that spring snowmelt triggers an abrupt transition in the composition of soil microbial communities of alpine grassland that is closely linked to shifts in soil microbial functioning and biogeochemical pools and fluxes. Further, by experimentally manipulating snow cover we show that this abrupt seasonal transition in wide-ranging microbial and biogeochemical soil properties is advanced by earlier snowmelt. Preceding winter conditions did not change the processes that take place during snowmelt. Our findings emphasise the importance of seasonal dynamics for soil microbial communities and the biogeochemical cycles that they regulate. Moreover, our findings suggest that earlier spring snowmelt due to climate change will have far reaching consequences for microbial communities and nutrient cycling in these globally widespread alpine ecosystems.Subject terms: Metagenomics, Climate-change ecology, Microbial ecology, Biogeochemistry, Soil microbiology     

Diversity and composition of macroinvertebrate communities in a rare inland salt marsh

Inland salt marshes are rare habitats in the Great Lakes region of North America, formed on salt deposits from the Silurian period. These patchy habitats are abiotically stressful for the freshwater invertebrates that live there, and provide an opportunity to study the relationship between stress and diversity. We used morphological and COI metabarcoding data to assess changes in diversity and composition across both space (a transect from the salt seep to an adjacent freshwater area) and time (three sampling seasons). Richness was significantly lower at the seep site with both datatypes, while metabarcoding data additionally showed reduced richness at the freshwater transect end, consistent with a pattern where intermediate levels of stress show higher diversity. We found complementary, rather than redundant, patterns of community composition using the two datatypes: not all taxa were equally sequenced with the metabarcoding protocol. We identified taxa that are abundant at the salt seep of the marsh, including biting midges (Culicoides) and ostracods (Heterocypris). We conclude that (as found in other studies) molecular and morphological work should be used in tandem to identify the biodiversity in this rare habitat. Additionally, salinity may be a driver of community membership in this system, though further ecological research is needed to rule out alternate hypotheses.     

Effects of 7-day amino acid infusion on renal growth, function, and renin-angiotensin system in fetal sheep

These experiments examined whether renal growth and the fetal renin-angiotensin system could be stimulated by infusion of amino acids and whether chronic amino acid infusions restored glomerulotubular balance, which had been disrupted during 4-h infusions. Five fetal sheep aged 122 +/- 1 days gestation received an infusion of alanine, glycine, proline and serine in 0.15 M saline at 0.22 mmol/min for 7 days. Six control fetuses were given saline at the same rate (5 ml/h). Kidney wet weights after amino acid infusion were 28% larger than control fetuses (P < 0.05), and renal angiotensinogen mRNA levels were approximately 2.6-fold higher (P < 0.005). Circulating renin levels and renal renin mRNA levels were suppressed (P < 0.05), and renal renin protein levels tended to be lower. Arterial pressure was increased, and there was a marked, sustained natriuresis and diuresis. Glomerular filtration rate and filtered sodium were approximately two-fold higher throughout infusion (P < 0.05). Fractional proximal sodium reabsorption, suppressed at 4 h (from 73.4 +/- 6.5 to 53.7 +/- 10.2%), did not return to control levels (36.1 +/- 3.4% on day 7, P < 0.05). Distal sodium reabsorption was markedly increased (from 79 +/- 25 to 261 +/- 75 mumol/min by day 7, P < 0.005), but this was not sufficient to restore glomerulotubular balance. The resultant high rates of sodium excretion led to hyponatremia and polyhydramnios. In conclusion, long-term amino acid infusions increased renal angiotensinogen gene expression, kidney weight, and distal nephron sodium reabsorptive capacity but failed to restore proximal and total glomerulotubular balance.     

Aging-associated reductions in AMP-activated protein kinase activity and mitochondrial biogenesis

Recent studies have demonstrated a strong relationship between aging-associated reductions in mitochondrial function, dysregulated intracellular lipid metabolism, and insulin resistance. Given the important role of the AMP-activated protein kinase (AMPK) in the regulation of fat oxidation and mitochondrial biogenesis, we examined AMPK activity in young and old rats and found that acute stimulation of AMPK-alpha(2) activity by 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and exercise was blunted in skeletal muscle of old rats. Furthermore, mitochondrial biogenesis in response to chronic activation of AMPK with beta-guanidinopropionic acid (beta-GPA) feeding was also diminished in old rats. These results suggest that aging-associated reductions in AMPK activity may be an important contributing factor in the reduced mitochondrial function and dysregulated intracellular lipid metabolism associated with aging.     

Biology of the shore fly Scatella stagnalis in rockwool under greenhouse conditions

The development times and survival of immature stages in rockwool and the fecundity and longevity of adult Scatella stagnalis were determined and stage-specific life-tables constructed for the species at constant 20 and 25 °C and at a fluctuating temperature (23–34 °C, mean 28.5 °C). Development time from egg to adult decreased with temperature, being 15.9±0.1 days at 20 °C, 11.4±0.1 days at 25 °C and 10.1±0.2 days at fluctuating temperature with mean of 28.5 °C. The lower threshold for egg-to-adult development was 6.4±2.7 °C and the total quantity of thermal energy required to complete development was 212.8±.0 °C. The proportion of females in two populations studied was 0.521. High temperature increased the mortality of pupae from 7% (20 °C) and 10% (25 °C) to 29% at 28.5 °C. At 25 °C, female longevity was 15.5±0.7 days and fecundity 315±19 eggs/female (20.4 eggs/female/day). Males lived for 22.0±1.1 days. At constant 25 °C, the net reproductive rate was 126.1 female eggs/female, generation time was 18.4 days, the doubling time of the population 5.3 days, and the intrinsic rate of increase (r _m) 0.263 day^–1.     

High-performance liquid chromatographic method for the determination of mycophenolate mofetil in human plasma

A method for the quantification of mycophenolate mofetil (MMF, CellCept) in plasma using solid-phase extraction and HPLC is described here. A solution of internal standard is added to a 0.5-ml plasma aliquot. The resulting sample is treated with water and dilute HCl and applied to a C₁₈ solid-phase extraction column. After a water wash, the MMF and internal standard are eluted with methanol-0.1 M citrate-phosphate buffer, pH 2.6 (80:20, v/v). A 20-μl aliquot of the eluate is injected onto a C₁₈ column (5 μm particle size, 150 × 4.6 mm I.D.) and eluted at ambient temperature with acetonitrile-0.05 M citrate-phosphate buffer, pH 3.6, containing 0.02 M heptanesulfonic acid (41:59, v/v). Quantification is achieved by UV detection at 254 nm. The method is reproducible, accurate and specific for MMF. Using 0.5 ml of plasma for analysis, the quantification limit is 0.400 μg/ml and the range is 0.400–20 μg/ml. Based on the stability profile of MMF in plasma, it is recommended that blood samples collected following intravenous infusion be immediately stored on ice and that plasma be prepared rapidly, immediately stored frozen at −80°C and analyzed within four months of collection.     

A possible role of adenylate cyclase in the longterm dietary regulation of insulin secretion from rat islets of Langerhans

1. Adenylate cyclase activity and patterns of insulin release in response to various concentrations of glucose were determined in islets of Langerhans isolated from starving, fed, or glucose-loaded rats. 2. Basal and glucagon-stimulated activities of adenylate cyclase were lower in islets from starved than from fed rats. The minimum glucose concentration required for stimulation of insulin secretion was higher, whereas the maximum secretory response to glucose was lower, in islets from starved than from fed rats. 3. Adenylate cyclase activity in islets of Langerhans obtained from fed rats loaded with glucose by intermittent intravenous or intraperitoneal injections over 5h was significantly higher than that seen in islets from normal fed rats. Islets obtained from glucose-loaded rats required a lower glucose concentration for stimulation of insulin secretion and attained a higher maximal response to glucose stimulation than those derived from fed rats. 4. Incubation in vitro of islets isolated from normal fed rats, for periods of 1 to 24h in the presence of high concentrations of glucose resulted in an activation of adenylate cyclase that occurred progressively from 2 to 7h and which was maintained during 24h of incubation. The increase of adenylate cyclase activity in isolated islets incubated for 4h in the presence of glucose was not prevented by addition of cycloheximide or actinomycin D. Galactose or 2-deoxyglucose was ineffective in increasing adenylate cyclase activity, and pyruvate (20mm) was less effective than glucose. 5. It is suggested that glucose or a glucose metabolite may exert long-term effects on islet cell adenylate cyclase.     

Analysis of Evolutionarily Independent Protein-RNA Complexes Yields a Criterion to Evaluate the Relevance of Prebiotic Scenarios

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Whole genome sequencing of a natural recombinant Toxoplasma gondii strain reveals chromosome sorting and local allelic variants

Background  

Toxoplasma gondii is a zoonotic parasite of global importance. In common with many protozoan parasites it has the capacity for sexual recombination, but current evidence suggests this is rarely employed. The global population structure is dominated by a small number of clonal genotypes, which exhibit biallelic variation and limited intralineage divergence. Little is known of the genotypes present in Africa despite the importance of AIDS-associated toxoplasmosis.     

Intraclass diversification of immunoglobulin heavy chain genes in the African lungfish

Lungfish (Dipnoi) are the closest living relatives to tetrapods, and they represent the transition from water to land during vertebrate evolution. Lungfish are armed with immunoglobulins (Igs), one of the hallmarks of the adaptive immune system of jawed vertebrates, but only three Ig forms have been characterized in Dipnoi to date. We report here a new diversity of Ig molecules in two African lungfish species (Protopterus dolloi and Protopterus annectens). The African lungfish Igs consist of three IgMs, two IgWs, three IgNs, and an IgQ, where both IgN and IgQ originated evidently from the IgW lineage. Our data also suggest that the IgH genes in the lungfish are organized in a transiting form from clusters (IgH loci in cartilaginous fish) to a translocon configuration (IgH locus in tetrapods). We propose that the intraclass diversification of the two primordial gnathostome Ig classes (IgM and IgW) as well as acquisition of new isotypes (IgN and IgQ) has allowed lungfish to acquire a complex and functionally diverse Ig repertoire to fight a variety of microorganisms. Furthermore, our results support the idea that “tetrapod-specific” Ig classes did not evolve until the vertebrate adaptation to land was completed ~360 million years ago.