The role of quorum sensing signalling in EPS production and the assembly of a sludge community into aerobic granules

Quorum sensing (QS) signalling has been extensively studied in single species populations. However, the ecological role of QS in complex, multi-species communities, particularly in the context of community assembly, has neither been experimentally explored nor theoretically addressed. Here, we performed a long-term bioreactor ecology study to address the links between QS, organization and composition of complex microbial communities. The conversion of floccular biomass to highly structured granules was found to be non-random, but strongly and positively correlated with N-acyl-homoserine-lactone (AHL)-mediated QS. Specific AHLs were elevated up to 100-fold and were strongly associated with the initiation of granulation. Similarly, the levels of particular AHLs decreased markedly during the granular disintegration phase. Metadata analysis indicated that granulation was accompanied by changes in extracellular polymeric substance (EPS) production and AHL add-back studies also resulted in increased EPS synthesis. In contrast to the commonly reported nanomolar to micromolar signal concentrations in pure culture laboratory systems, QS signalling in the granulation ecosystem occurred at picomolar to nanomolar concentrations of AHLs. Given that low concentrations of AHLs quantified in this study were sufficient to activate AHL bioreporters in situ in complex granular communities, AHL mediated QS may be a common feature in many natural and engineered ecosystems, where it coordinates community behaviour.     

Allelic Variation in a Willow Warbler Genomic Region Is Associated with Climate Clines

Local adaptation is an important process contributing to population differentiation which can occur in continuous or isolated populations connected by various amounts of gene flow. The willow warbler (Phylloscopus trochilus) is one of the most common songbirds in Fennoscandia. It has a continuous breeding distribution where it is found in all forested habitats from sea level to the tree line and therefore constitutes an ideal species for the study of locally adapted genes associated with environmental gradients. Previous studies in this species identified a genetic marker (AFLP-WW1) that showed a steep north-south cline in central Sweden with one allele associated with coastal lowland habitats and the other with mountainous habitats. It was further demonstrated that this marker is embedded in a highly differentiated chromosome region that spans several megabases. In the present study, we sampled 2,355 individuals at 128 sites across all of Fennoscandia to study the geographic and climatic variables associated with the allele frequency distributions of WW1. Our results demonstrate that 1) allele frequency patterns significantly differ between mountain and lowland populations, 2) these allele differences coincide with extreme temperature conditions and the short growing season in the mountains, and milder conditions in coastal areas, and 3) the northern-allele or “altitude variant” of WW1 occurs in willow warblers that occupy mountainous habitat regardless of subspecies. Finally these results suggest that climate may exert selection on the genomic region associated with these alleles and would allow us to develop testable predictions for the distribution of the genetic marker based on climate change scenarios.     

Extracellular Water and Blood Pressure in Adults with Growth Hormone (GH) Deficiency: A Genotype-Phenotype Association Study

Objectives

Growth hormone deficiency (GHD) in adults is associated with decreased extracellular water volume (ECW). In response to GH replacement therapy (GHRT), ECW increases and blood pressure (BP) reduces or remains unchanged. Our primary aim was to study the association between polymorphisms in genes related to renal tubular function with ECW and BP before and 1 year after GHRT. The ECW measures using bioimpedance analysis (BIA) and bioimpedance spectroscopy (BIS) were validated against a reference method, the sodium bromide dilution method (Br⁻).

Design and Methods

Using a candidate gene approach, fifteen single-nucleotide polymorphisms (SNPs) in nine genes with known impact on renal tubular function (AGT, SCNN1A, SCNN1G, SLC12A1, SLC12A3, KCNJ1, STK39, WNK1 and CASR) were genotyped and analyzed for associations with ECW and BP at baseline and with their changes after 1 year of GHRT in 311 adult GHD patients. ECW was measured with the Br⁻, BIA, and BIS.

Results

Both BIA and BIS measurements demonstrated similar ECW results as the reference method. At baseline, after adjustment for sex and BMI, SNP rs2291340 in the SLC12A1 gene was associated with ECW volume in GHD patients (p = 0.039). None of the SNPs influenced the ECW response to GHRT. One SNP in the SLC12A3 gene (rs11643718; p = 0.024) and three SNPs in the SCNN1G gene [rs5723 (p = 0.02), rs5729 (p = 0.016) and rs13331086 (p = 0.035)] were associated with the inter-individual differences in BP levels at baseline. A polymorphism in the calcium-sensing receptor (CASR) gene (rs1965357) was associated with changes in systolic BP after GHRT (p = 0.036). None of these associations remained statistically significant when corrected for multiple testing.

Conclusion

The BIA and BIS are as accurate as Br⁻ to measure ECW in GHD adults before and during GHRT. Our study provides the first evidence that individual polymorphisms may have clinically relevant effects on ECW and BP in GHD adults.     

The Escherichia coli BarA-UvrY two-component system is a virulence determinant in the urinary tract

Background  

The Salmonella enterica BarA-SirA, the Erwinia carotovora ExpS-ExpA, the Vibrio cholerae BarA-VarA and the Pseudomonas spp GacS-GacA all belong to the same orthologous family of two-component systems as the Escherichia coli BarA-UvrY. In the first four species it has been demonstrated that disruption of this two-component system leads to a clear reduction in virulence of the bacteria. Our aim was to determine if the Escherichia coli BarA-UvrY two-component system is connected with virulence using a monkey cystitis model.     

Electronic interactions and energy transfer in oligothiophene-linked bis-porphyrins.

The photophysical and spectroscopic properties of a series of bis-porphyrin compounds meso-meso-linked via oligothiophene bridges are reported. In particular the effects of the different bridges on the porphyrin properties as well as their ability to enhance energy transfer is investigated. The main findings are: a splitting of the degeneracy of the porphyrin Soret band transition with a lower energy transition aligned along the bridge, a dramatic decrease in triplet lifetime and the occurrence of "superexchange" as the main mechanism for mediating singlet-singlet energy transfer in the case where the bridge is a quaterthiophene. Our results show significant perturbations of the intrinsic porphyrin properties induced by the bridge, which are important for the function of porphyrin assemblies.     

Spreading introgression in the wake of a moving contact zone

An increasing number of studies describe moving hybrid zones. This raises the issue of their actual frequency and emphasizes the need for methods that enable the detection of zone movements without historical records. Asymmetric introgression, usually considered as a signature of geographical shift, might be misleading when applied to mitochondrial or potentially non-neutral markers. We investigated mitochondrial and genomic introgression, using 30 AFLP derived markers, in a well-documented moving avian contact zone between two warblers. We found no instances of cross-species transmission of mitochondrial DNA but we detected nuclear introgression. Introgression levels were higher in the expanding species. Highest introgression was observed in populations that recently became allopatric than in current sympatric populations, which suggests that alien genetic material mainly spread at the time just before the receding species became extinct. We propose that either local recruitment or positive selection on some loci contribute to this pattern. Furthermore, we propose that, when the rarefaction of sexual partners drive the hybridization process, movement could be revealed by introgression peaking on the rear edge of the moving zone, or in its close vicinity.     

Environmental impacts of forest production and supply of pulpwood: Spanish and Swedish case studies

Background, aim and scope  Forest operations use large amounts of energy, which must be considered when life cycle assessment (LCA) methodology is applied to forest products. Forest management practices differ considerably between countries and may also differ within a country. This paper aims to identify and compare the environmental burdens from forest operations in Sweden and Spain focused on pulpwood production and supply to pulp mills. Materials and methods  To perform the analysis, the main forest plantations were investigated as well as the most important tree species used in pulp mills in both countries: eucalyptus and, Norway spruce and Scots pine, were taken into account for the Spanish and Swedish case studies, respectively. Energy requirements for pulpwood production and supply to Spanish and Swedish pulp mills are evaluated in this paper. All forest operations from site preparation to extraction of felled wood to the delivery point at the roadside are included within the system boundaries as well as wood transport from forest landing to the pulp mill gate. Seedling and machinery production are excluded from the system boundaries due to lack of field data. The impact assessment phase was carried out according to the Swedish Environmental Management Council and, in particular, the impact categories assessed in forest and agricultural LCAs (global warming, acidification, eutrophication and photochemical oxidant formation) were analysed. SimaPro 7.10 software was used to perform the impact assessment stage. Results  Different types of wood are produced in both case studies: softwood in Sweden and hardwood in Spain, with higher production of round wood and biomass per hectare in Sweden. Total energy use for pulpwood production and supply are in a similar order of magnitude, up to 395 MJ and 370 MJ/m³ solid under bark in Spain and Sweden, respectively. Field operations, such as silviculture and logging, are more energy-intensive in the Spanish case study. However, secondary hauling of pulpwood to pulp mill requires more energy in the Swedish case study. These important differences are related to different forest management practices as well as to pulpwood supply to the pulp mill. The eventual imports of pulpwood, application of pesticides, thinning step or final felling considerably affects energy requirements, which are reflected on the environmental results. Discussion  Although differences between both case studies were observed, several stages were investigated: wood delivery to the pulp mill by road, harvesting and forwarding, contribute considerably to acidification, eutrophication and global warming potential in both cases. The type of wood, the machines used in forest operations (mechanised or motor-manual), the use of fossil fuels and the amount of wood produced influence the results. These differences must be kept in mind in comparative studies between such different countries. Conclusions  The results obtained in this work allow one to forecast the importance of forest operations in LCA of forest products (in this case, wood pulp) and the influence of energy use in the results. Special attention has been paid in the inventory analysis stage for both case studies. It is possible to gain a better environmental performance in both case studies if alternative practices are considered, mainly focused on site preparation and stand tending in the Spanish system and on pulpwood supply in the Swedish one. Recommendations and perspectives  This study provides useful information that can assist forest-based industries in the aim of increasing their sustainability. Future work will focus on the study of several transport alternatives of pulpwood supply including railway, road and ship. In addition, pulpwood processing in Spanish and Swedish paper pulp mills considered to be representative of the “state of art” will be carried out in order to get a complete picture of this kind of forest-based industry. In addition, the use of biofuels (such as forest biomass) instead of fossil fuels and CO₂ uptake of wood via photosynthesis will be carried out in order to have a complete perspective of forest ecosystems.     

Computerized Determination of Adipocyte Size

Objective: Fat cell size is a fundamental parameter in the study of adipose tissue metabolism, because it markedly influences the cellular rates of metabolism. Previous techniques for the sizing of adipocytes are often complicated or time‐consuming. The aim of this study was to develop a new, computerized method for rapid and accurate determination of adipocyte size in a cell suspension obtained by incubating human or rat adipose tissue biopsies with collagenase. Research Methods and Procedures: The cell suspension was placed between a siliconized glass slide and a cover slip. Using the reference method [designated as (R)], the cell diameters were determined manually using a microscope with a calibrated ocular. The new method presented here [designated as (C)] was based on computerized image analysis. Results: After two well‐defined corrective adjustments, measurements with (R) and (C) agreed very well. The small remaining differences seemed, in fact, to depend on inconsistencies in (R). Discussion: We propose that (C) constitutes a valuable tool to study fat cell size, because this method is fast and allows the assessment of a sufficient number of cells to get reliable data on size distribution. Furthermore, images of cell preparations may be stored for future reference.     

Isolation and long-term serial cultivation of endothelial cells from the microvessels of the adult human dermis

Sumamry A method to isolate and maintain microvascular endothelial cells from the cutaneous vessels of adult human skin in long-term culture has been developed. Endothelial cells lining the microvessels of the papillary dermis are released from surrounding tissue during a brief trypsin incubation (0.3% trypsin, 1% EDTA). Cells are plated onto a fibronectin substrate and maintained in Leibovitz (L15) culture medium containing pooled human serum (50%) and antibiotics. Proliferation is dependent upon the presence of several additional growth factors, cholera enterotoxin (1×10⁻⁹ M), isobutyl methylxanthine (3.3×10⁻⁵ M), and medium conditioned by explant culture of the mouse EHS sarcoma. Using this supplemented medium, cells proliferate readily and can be cultivated serially for more than 6 passages (3 months in vitro). These cells retain their characteristic endothelial cell morphology, stain positively for Factor VIII antigen, and contain Weibel-Palade bodies. This research was supported by grant AG 01312 from the U.S. Public Health Service, Washington, D.C.