Geographical patterns of micro‐organismal community structure: are diatoms ubiquitously distributed across boreal streams?

A topic under intensive study in community ecology and biogeography is the degree to which microscopic, as well as macroscopic organisms, show spatially-structured variation in community characteristics. In general, unicellular microscopic organisms are regarded as ubiquitously distributed and, therefore, without a clear biogeographic signal. This view was summarized 75  years ago by Baas-Becking, who stated "everything is everywhere, but, the environment selects". Within the context of metacommunity theory, this hypothesis is congruent with the species sorting model. By using a broad-scale dataset on stream diatom communities and environmental predictor variables across most of Finland, our main aim was to test this hypothesis. Patterns of spatial autocorrelation were evaluated by Moran's I based correlograms, whereas partial regression analysis and partial redundancy analysis were used to quantify the relative importance of environmental and spatial factors on total species richness and on community composition, respectively. Significant patterns of spatial autocorrelation were found for all environmental variables, which also varied widely. Our main results were clear-cut. In general, pure spatial effects clearly overcame those of environmental effects, with the former explaining much more variation in species richness and community composition. Most likely, missing environmental variables cannot explain the higher predictive power of spatial variables, because we measured key factors that have previously been found to be the most important variables (e.g. pH, conductivity, colour, phosphorus, nitrogen) shaping the structure of diatom communities. Therefore, our results provided only limited support for the Baas-Becking hypothesis and the species sorting perspective of metacommunity theory.     

Balancing the needs of capercaillie (Tetrao urogallus) and moose (Alces alces) in large-scale human land use

The capercaillie has been negatively affected by the loss of mature forests. However, forestry creates young plantations offering a superabundant food supply for moose. Using two spatial scales, we tested whether the landscape-level environmental requirements of the capercaillie and moose differ. We compared the spatial association between the abundances of the two species in 50-?×?50-km grids and, using a set of regression models, analyzed how it was affected by various land use variables in five regions of Finland. Both species were generally most abundant in the same grid cells. Moreover, the association between abundance and several landscape variables was very similar for both species. Forest cover had a positive impact on both species in Eastern and South-Western Finland. Only in Western Finland was the capercaillie more positively associated with older forest than the moose. Human impact variables were negatively related to both capercaillie and moose abundance in Eastern and South-Western Finland, the effect being stronger for capercaillie. In Northern Finland, human impact turned positive. Our results highlight that, on broad landscape and regional scales, we might not need to make trade-offs in management decisions concerning capercaillie and moose. While considering regional land use planning, the primary goal for both species seems to be to secure large areas of forest, preferably at a distance from human settlement.     

Knitting patterns of biodiversity,range size and body size in aquatic beetle faunas: significant relationships but slightly divergent drivers

1. Ecogeographical rules refer to recurring patterns in nature, including the latitudinal diversity gradient (LDG), Rapoport's rule and Bergmann's rule, amongst others. In the present study, the existence of these rules was examined for diving beetles (Coleoptera: Dytiscidae), a family of aquatic predatory beetles. 2. Assemblage‐level data were analysed for diving beetles, focusing on species richness, local contribution to beta diversity (LCBD), mean range size and mean body size across the biogeographical provinces of Northern Europe. First, each of these variables was correlated with latitude, and then variation in each variable was modelled using actual environmental variables in boosted regression tree analysis. 3. Species richness was found to decrease with latitude, LCBD increased with latitude, mean range size did not show a significant relationship with latitude, and mean body size decreased with latitude. The latter finding was in contrast to Bergmann's rule. The actual environmental variables best predicting variation in these four response variables varied among the models, although they generally included temperature‐related and land use variables as the most influential ones. 4. The results obtained in the present study suggest that diving beetles conformed to the LDG, did not follow Rapoport's rule, and showed a reversed latitudinal gradient in the context of Bergmann's rule. In addition, species‐poor provinces harboured ecologically most unique faunas, suggesting that species richness and LCBD are complementary measures of biodiversity. 5. Even though general support was not found for most of the ecogeographical rules examined, the findings of the present study are interesting because they suggest that aquatic ectothermic invertebrates may show patterns different from those originally described for terrestrial endothermic vertebrates.     

DNA bending by the human damage recognition complex XPC-HR23B

Genome integrity is maintained, despite constant assault on DNA, due to the action of a variety of DNA repair pathways. Nucleotide excision repair (NER) protects the genome from the deleterious effects of UV irradiation as well as other agents that induce chemical changes in DNA bases. The mechanistic steps required for eukaryotic NER involve the concerted action of at least six proteins or protein complexes. The specificity to incise only the DNA strand including the damage at defined positions is determined by the coordinated assembly of active protein complexes onto damaged DNA. In order to understand the molecular mechanism of the NER reactions and the origin of this specificity and control we analyzed the architecture of functional NER complexes at nanometer resolution by scanning force microscopy (SFM). In the initial step of damage recognition by XPC-HR23B we observe a protein induced change in DNA conformation. XPC-HR23B induces a bend in DNA upon binding and this is stabilized at the site of damage. We discuss the importance of the XPC-HR23B-induced distortion as an architectural feature that can be exploited for subsequent assembly of an active NER complex.     

Associations between multimorbidity and adverse health outcomes in UK Biobank and the SAIL Databank: A comparison of longitudinal cohort studies

BackgroundCohorts such as UK Biobank are increasingly used to study multimorbidity; however, there are concerns that lack of representativeness may lead to biased results. This study aims to compare associations between multimorbidity and adverse health outcomes in UK Biobank and a nationally representative sample.Methods and findingsThese are observational analyses of cohorts identified from linked routine healthcare data from UK Biobank participants (n = 211,597 from England, Scotland, and Wales with linked primary care data, age 40 to 70, mean age 56.5 years, 54.6% women, baseline assessment 2006 to 2010) and from the Secure Anonymised Information Linkage (SAIL) databank (n = 852,055 from Wales, age 40 to 70, mean age 54.2, 50.0% women, baseline January 2011). Multimorbidity (n = 40 long-term conditions [LTCs]) was identified from primary care Read codes and quantified using a simple count and a weighted score. Individual LTCs and LTC combinations were also assessed. Associations with all-cause mortality, unscheduled hospitalisation, and major adverse cardiovascular events (MACEs) were assessed using Weibull or negative binomial models adjusted for age, sex, and socioeconomic status, over 7.5 years follow-up for both datasets.Multimorbidity was less common in UK Biobank than SAIL (26.9% and 33.0% with ≥2 LTCs in UK Biobank and SAIL, respectively). This difference was attenuated, but persisted, after standardising by age, sex, and socioeconomic status. The association between increasing multimorbidity count and mortality, hospitalisation, and MACE was similar between both datasets at LTC counts of ≤3; however, above this level, UK Biobank underestimated the risk associated with multimorbidity (e.g., mortality hazard ratio for 2 LTCs 1.62 (95% confidence interval 1.57 to 1.68) in SAIL and 1.51 (1.43 to 1.59) in UK Biobank, hazard ratio for 5 LTCs was 3.46 (3.31 to 3.61) in SAIL and 2.88 (2.63 to 3.15) in UK Biobank). Absolute risk of mortality, hospitalisation, and MACE, at all levels of multimorbidity, was lower in UK Biobank than SAIL (adjusting for age, sex, and socioeconomic status). Both cohorts produced similar hazard ratios for some LTCs (e.g., hypertension and coronary heart disease), but UK Biobank underestimated the risk for others (e.g., alcohol-related disorders or mental health conditions). Hazard ratios for some LTC combinations were similar between the cohorts (e.g., cardiovascular conditions); however, UK Biobank underestimated the risk for combinations including other conditions (e.g., mental health conditions). The main limitations are that SAIL databank represents only part of the UK (Wales only) and that in both cohorts we lacked data on severity of the LTCs included.ConclusionsIn this study, we observed that UK Biobank accurately estimates relative risk of mortality, unscheduled hospitalisation, and MACE associated with LTC counts ≤3. However, for counts ≥4, and for some LTC combinations, estimates of magnitude of association from UK Biobank are likely to be conservative. Researchers should be mindful of these limitations of UK Biobank when conducting and interpreting analyses of multimorbidity. Nonetheless, the richness of data available in UK Biobank does offers opportunities to better understand multimorbidity, particularly where complementary data sources less susceptible to selection bias can be used to inform and qualify analyses of UK Biobank.

Peter Hanlon and colleagues compare the associations between multimorbidity and adverse health outcomes in UK Biobank and the SAIL Databank.     

An immunologically cryptic epitope of Plasmodium falciparum circumsporozoite protein facilitates liver cell recognition and induces protective antibodies that block liver cell invasion

Circumsporozoite, a predominant surface protein, is involved in invasion of liver cells by Plasmodium sporozoites, which leads to malaria. We have previously reported that the amino terminus region (amino acids 27-117) of P. falciparum circumsporozoite protein plays a critical role in the invasion of liver cells by the parasite. Here we show that invasion-blocking antibodies are induced by a polypeptide encoding these 91 amino acids, only when it is presented in the absence of the rest of the protein. This suggests that when present in the whole protein, the amino terminus remains immunologically cryptic. A single reactive epitope was identified and mapped to a stretch of 21 amino acids from position 93 to 113. The epitope is configurational in nature, since its recognition was affected by deleting as little as 3 amino acids from either end of the 21-residue peptide. Lysine 104, the only known polymorphic position in the epitope, affected its recognition by the antibodies, and its conversion to leucine in the protein led to a substantial loss of binding activity of the protein to the hepatocytes. This indicated that in the protein, the epitope serves as a binding ligand and facilitates the interaction between sporozoite and hepatic cells. When considered along with the observation that in its native state this motif is immunologically unresponsive, we suggest that hiding functional moieties of the protein from the immune system is an evasion strategy to preserve liver cell binding function and may be of importance in designing anti-sporozoite vaccines.     

Polyelectrolyte brushes grafted from cellulose nanocrystals using Cu-mediated surface-initiated controlled radical polymerization

Herein we report the synthesis of cellulose nanocrystals (CNCs) grafted with poly(acrylic acid) (PAA) chains of different lengths using Cu-mediated surface initiated-controlled radical polymerization (SI-CRP). First, poly(tert-butylacrylate) (PtBA) brushes were synthesized; then, subsequent acid hydrolysis was used to furnish PAA brushes tethered onto the CNC surfaces. The CNCs were chemically modified to create initiator moieties on the CNC surfaces using chemical vapor deposition (CVD) and continued in solvent phase in DMF. A density of initiator groups of 4.6 bromine ester groups/nm(2) on the CNC surface was reached, suggesting a dense functionalization and a promising starting point for the controlled/living radical polymerization. The SI-CRP of tert-butylacrylate proceeded in a well-controlled manner with the aid of added sacrificial initiator, yielding polymer brushes with polydispersity values typically well below 1.12. We calculated the polymer brush grafting density to almost 0.3 chains/nm(2), corresponding to high grafting densities and dense polymer brush formation on the nanocrystals. Successful rapid acid hydrolysis to remove the tert-butyl groups yielded pH-responsive PAA-polyelectrolyte brushes bound to the CNC surface. Individually dispersed rod-like nanoparticles with brushes of PtBA or PAA were clearly visualized by AFM and TEM imaging.