Environmental Controls on Microbial Abundance and Activity on the Greenland Ice Sheet: A Multivariate Analysis Approach

Microbes in supraglacial ecosystems have been proposed to be significant contributors to regional and possibly global carbon cycling, and quantifying the biogeochemical cycling of carbon in glacial ecosystems is of great significance for global carbon flow estimations. Here we present data on microbial abundance and productivity, collected along a transect across the ablation zone of the Greenland ice sheet (GrIS) in summer 2010. We analyse the relationships between the physical, chemical and biological variables using multivariate statistical analysis. Concentrations of debris-bound nutrients increased with distance from the ice sheet margin, as did both cell numbers and activity rates before reaching a peak (photosynthesis) or a plateau (respiration, abundance) between 10 and 20 km from the margin. The results of productivity measurements suggest an overall net autotrophy on the GrIS and support the proposed role of ice sheet ecosystems in carbon cycling as regional sinks of CO₂ and places of production of organic matter that can be a potential source of nutrients for downstream ecosystems. Principal component analysis based on chemical and biological data revealed three clusters of sites, corresponding to three ‘glacier ecological zones’, confirmed by a redundancy analysis (RDA) using physical data as predictors. RDA using data from the largest ‘bare ice zone’ showed that glacier surface slope, a proxy for melt water flow, accounted for most of the variation in the data. Variation in the chemical data was fully explainable by the determined physical variables. Abundance of phototrophic microbes and their proportion in the community were identified as significant controls of the carbon cycling-related microbial processes.     

Proteomic analysis of the impact of static culturing on the expansion of rat bone marrow mesenchymal stem cells

The clinical potential of mesenchymal stem cells (MSC) in tissue engineering and regenerative medicine is due to their self-renewal, proliferation and multi-lineage differentiation potential. Clinical use requires large cell numbers; which can, theoretically, be generated by ex vivo expansion of plastic adherent, MSC subpopulation, of bone marrow cells (BMC). Effects of serial culture on MSC phenotype were investigated using non-gel based quantitative proteomic methodology for static monolayer cultures of rat BMC. In total, 382 proteins were relatively quantified (≥ 2 peptides). Nine proteins were up-regulated and seven down-regulated at passage 4 relative to passage 2 (p ≤ 0.05). We propose that serial culture impacts on MSC expansion (observed decline in colony forming potential and colony size) is through a combination of osteogenic differentiation and ageing/senescence and propose six novel protein biomarkers as candidates for quality control purposes in bioprocessing.     

Renoprotective effects of anti-TGF-β antibody and antihypertensive therapies in Dahl S rats

This study examined the effects of anti-TGF-β antibody (1D11) therapy in Dahl S (S) rats fed a 4% NaCl diet. Baseline renal expression of TGF-β1 and the degree of injury were lower in female than male S rats maintained on a 0.4% NaCl diet. 4% NaCl diet increased mean arterial pressure (MAP), proteinuria, and renal injury to the same extent in both male and female S rats. Chronic treatment with 1D11 had renoprotective effects in both sexes. The ability of 1D11 to oppose the development of proteinuria when given alone or in combination with antihypertensive agents was further studied in 6-wk-old female S rats, since baseline renal injury was less than that seen in male rats. 1D11, diltiazem, and hydrochlorothiazide (HCT) attenuated the development of hypertension, proteinuria, and glomerular injury. 1D11 had no additional effect when given in combination with these antihypertensive agents. We also explored whether 1D11 could reverse renal injury in 9-wk-old male S rats with preexisting renal injury. MAP increased to 197 ± 4 mmHg and proteinuria rose to >300 mg/day after 3 wk on a 4% NaCl diet. Proteinuria was reduced by 30-40% in rats treated with 1D11, HCT, or captopril + 1D11, but the protective effect was lost in rats fed the 4% NaCl diet for 6 wk. Nevertheless, 1D11, HCT, and captopril + 1D11 still reduced renomedullary and cardiac fibrosis. These results indicate that anti-TGF-β antibody therapy reduces renal and cardiac fibrosis and affords additional renoprotection when given in combination with various antihypertensive agents in Dahl S rats.     

Molecular cloning and characterisation of a novel P-glycoprotein in the salmon louse Lepeophtheirus salmonis

The salmon louse, Lepeophtheirus salmonis, is a crustacean ectoparasite of salmonid fish. At present, sea louse control on salmon farms relies heavily upon chemical treatments. Drug efflux transport, mediated by ABC transporters such as P-glycoprotein (Pgp), represents a major mechanism for drug resistance in parasites. We report here the molecular cloning of a new Pgp from the salmon louse, called SL-PGY1. A partial Pgp sequence was obtained by searching sea louse ESTs, and extended by rapid amplification of cDNA ends (RACE). The open reading frame of SL-PGY1 encodes a protein of 1438 amino acids that possesses typical structural traits of P-glycoproteins, and shows a high degree of sequence homology to invertebrate and vertebrate P-glycoproteins. In the absence of drug exposure, SL-PGY1 mRNA expression levels did not differ between a drug-susceptible strain of L. salmonis and a strain showing a ~7-fold decrease in sensitivity against emamectin benzoate, the active component of the in-feed sea louse treatment SLICE (Merck Animal Health). Aqueous exposure of the hyposensitive salmon louse strain to emamectin benzoate (24h, 410 μg/L) provoked a 2.9-fold upregulation of SL-PGY1. Adult male lice of both strains showed a greater abundance of SL-PGY1 mRNA than adult females.     

Meeting report: a symposium on the evolution of common molecular pathways underlying innate immunity

The University of California, Davis hosted a symposium on innate immunity in January 2012. Professors Bruce Beutler, Jules Hoffmann, Luke O'Neill and Pamela Ronald discussed their research on mechanisms that multicellular organisms use to recognize microbes.     

Insect occurrence in agricultural land-uses depends on realized niche and geographic range properties

Geographic range size predicts species’ responses to land-use change and intensification, but the reason why is not well established because many correlates of larger geographic ranges, such as realized niche breadth, may mediate species’ responses to environmental change. Agricultural land uses (hereafter ‘agroecosystems’) have warm, dry and more variable microclimates than do cooler and wetter mature forests, so are predicted to filter for species that have warmer, drier and broader fundamental and realized niches. To test these predictions, we estimated species’ realized niches, for temperature and precipitation, and geographic range sizes of 764 insect species by matching GBIF occurrence records to global climate layers, and modelled how species presence/absence in mature forest and nearby agroecosystems depend on species’ realized niches or geographic ranges. The predicted species niche effects consistently matched the expected direction of microclimatic transition from mature forest to agroecosystems. We found a clear signal that species with preference for warmer and drier climates were more likely to be present in agroecosystems. In addition, the probability that species occurred in different land-use types was predicted better by species’ realized niche than their geographic range size. However, niche effects are often context-dependent and varied amongst studies, taxonomic groups and regions used in this analysis: predicting which particular aspects of species’ realized niche cause sensitivity to land-use change, and the underpinning mechanisms, remains a major challenge for future research and multiple components of species’ realized niches may be important to consider. Using realized niches derived from open-source occurrence records can be a simple and widely applicable tool to help identify when biodiversity responds to the microclimate component of land-use change.