Resolution of Conflicting Signals at the Single-Cell Level in the Regulation of Cyanobacterial Photosynthesis and Nitrogen Fixation

Unicellular, diazotrophic cyanobacteria temporally separate dinitrogen (N-2) fixation and photosynthesis to prevent inactivation of the nitrogenase by oxygen. This temporal segregation is regulated by a circadian clock with oscillating activities of N-2 fixation in the dark and photosynthesis in the light. On the population level, this separation is not always complete, since the two processes can overlap during transitions from dark to light. How do single cells avoid inactivation of nitrogenase during these periods? One possibility is that phenotypic heterogeneity in populations leads to segregation of the two processes. Here, we measured N-2 fixation and photosynthesis of individual cells using nanometer-scale secondary ion mass spectrometry (nanoSIMS) to assess both processes in a culture of the unicellular, diazotrophic cyanobacterium Crocosphaera watsonii during a dark-light and a continuous light phase. We compared single-cell rates with bulk rates and gene expression profiles. During the regular dark and light phases, C. watsonii exhibited the temporal segregation of N-2 fixation and photosynthesis commonly observed. However, N-2 fixation and photosynthesis were concurrently measurable at the population level during the subjective dark phase in which cells were kept in the light rather than returned to the expected dark phase. At the single-cell level, though, cells discriminated against either one of the two processes. Cells that showed high levels of photosynthesis had low nitrogen fixing activities, and vice versa. These results suggest that, under ambiguous environmental signals, single cells discriminate against either photosynthesis or nitrogen fixation, and thereby might reduce costs associated with running incompatible processes in the same cell

Live-Cell Visualization of Pre-mRNA Splicing with Single-Molecule Sensitivity

SummaryRemoval of introns from pre-messenger RNAs (pre-mRNAs) via splicing provides a versatile means of genetic regulation that is often disrupted in human diseases. To decipher how splicing occurs in real time, we directly examined with single-molecule sensitivity the kinetics of intron excision from pre-mRNA in the nucleus of living human cells. By using two different RNA labeling methods, MS2 and λN, we show that β-globin introns are transcribed and excised in 20–30 s. Furthermore, we show that replacing the weak polypyrimidine (Py) tract in mouse immunoglobulin μ (IgM) pre-mRNA by a U-rich Py decreases the intron lifetime, thus providing direct evidence that splice-site strength influences splicing kinetics. We also found that RNA polymerase II transcribes at elongation rates ranging between 3 and 6 kb min−1 and that transcription can be rate limiting for splicing. These results have important implications for a mechanistic understanding of cotranscriptional splicing regulation in the live-cell context

Faecalibacterium prausnitzii Strain HTF-F and Its Extracellular Polymeric Matrix Attenuate Clinical Parameters in DSS-Induced Colitis

Date of Acceptance: 26/02/2015 Funding: The authors received no specific funding for this work.Peer reviewedPublisher PD

Predicting the impacts of chemical pollutants on animal groups

Wildlife are exposed to an increasing number and diversity of chemical pollutants.Chemical pollutants can elicit a range of sublethal effects on individual organisms, but research on how these contaminants affect social interactions and animal groups is severely lacking.It is imperative that perspectives from behavioural ecology and ecotoxicology are integrated, to increase our understanding of how contaminant effects on individuals might cascade to group-level processes.We present a conceptual framework for researchers and practitioners to guide the study of how chemical pollutants might affect the emergence, organisation, and function of animal social groups.Chemical pollution is among the fastest-growing agents of global change. Synthetic chemicals with diverse modes-of-action are being detected in the tissues of wildlife and pervade entire food webs. Although such pollutants can elicit a range of sublethal effects on individual organisms, research on how chemical pollutants affect animal groups is severely lacking. Here we synthesise research from two related, but largely segregated fields – ecotoxicology and behavioural ecology – to examine pathways by which chemical contaminants could disrupt processes that govern the emergence, self-organisation, and collective function of animal groups. Our review provides a roadmap for prioritising the study of chemical pollutants within the context of sociality and highlights important methodological advancements for future research

Outcome of protease inhibitor substitution with nevirapine in HIV-1 infected children

<p>Abstract</p> <p>Background</p> <p>Protease inhibitors (PIs) have been associated with metabolic complications. There is a trend to switch to simpler therapy to improve these disturbances. We report a case-series describing the effects in metabolic abnormalities in seven HIV-infected children, previously treated with protease inhibitor (PI) after switching to nevirapine.</p> <p>Methods</p> <p>Seven children with stable PI-containing regimen and a long lasting HIV-1 RNA < 50 copies/ml were switched to nevirapine. All patients were naïve to non nucleoside reverse transcriptase inhibitor. PIs were switched to nevirapine. Preentry nucleoside reverse transcriptase inhibitors were maintained. The substitution of PIs with nevirapine was made when the patient showed hyperlipidemia or lipodystrophy or the physician and/or the patient's willingness to simplify. Clinical, laboratory data and anthropometric parameters were assessed every 3 months. Dual-energy X-Ray absorptiometry scans (DXA) was performed at baseline and at 12 months.</p> <p>Results</p> <p>Seven HIV-infected children were enrolled. Median age: 130 months (99,177). Median baseline CD4%: 32%. All had HIV-1 RNA < 50 copies/ml. Median length of preentry PI-therapy was 47 months (28, 91). Median age at the beginning of nevirapine was 120 months (99,177). Median decrease in cholesterol in 7.2 mmol/L was observed (P = 0.09), from baseline to 12 months. HDL-cholesterol increased in 5.1 mmol/L (P = 0.03) throughout the study period. No significant changes were observed in DXA with regard to body fat, but changes in total body bone mineral content and lean body content were significant. CD4% remained stable. All patients but one maintained viral load < 50 copies/ml at 12 months. The patient with virologic failure referred bad adherence. Children referred to take medication more easily.</p> <p>Conclusion</p> <p>PI substitution with nevirapine improved lipid profile in our patients, although this strategy did not show significant changes in body fat or lipodystrophy.</p

Seasonal temperature trends on the Spanish mainland: A secular study (1916–2015)

Trends in seasonal mean values of maximum and minimum temperature are analysed in the Spanish mainland from the new MOTEDAS_century database. This new data set has been developed combining the digitalized archives from the Spanish Meteorological Agency (AEMET) with information retrieved from Annual Books published by the former Meteorological Agency dating back to 1916, and covers the period 1916–2015. In all four seasons, mean seasonal temperature of maximum (Tmax) and minimum (Tmin) increased. The raising occurred in two main pulses separated by a first pause around the middle of the 20th century, but differed among seasons and also between maximum and minimum temperature. Analysis of the percentage of land affected by significant trends in maximum temperature reveals two increasing phases in spring and summer for Tmax, and in spring, summer, and autumn for Tmin. However, winter Tmax only rose during the recent decades, and autumn Tmax in the first decades. Negative significant trends were found in extended areas in spring Tmax, and in spring, autumn, and summer Tmin, confirming the first pause around the 1940's–1960's. Trends of seasonal mean values of Tmax and Tmin are not significant for at least the last 25–35 years of the study period, depending on the season. The areas under significant positive trend are usually more extended for Tmin than Tmax at any season and period. Areas with significant trend expand and contract in time according to two spatial gradients: south-east to north-west (east-west) for Tmax, and west to east for Tmin. We hypothesize a relationship between atmospheric prevalent advection and relief as triggering factors to understand spatial and temporal differences in seasonal temperatures at regional scale during the 20th century in the Iberian Peninsula