Differential Response of High-Elevation Planktonic Bacterial Community Structure and Metabolism to Experimental Nutrient Enrichment

Nutrient enrichment of high-elevation freshwater ecosystems by atmospheric deposition is increasing worldwide, and bacteria are a key conduit for the metabolism of organic matter in these oligotrophic environments. We conducted two distinct in situ microcosm experiments in a high-elevation lake (Emerald Lake, Sierra Nevada, California, USA) to evaluate responses in bacterioplankton growth, carbon utilization, and community structure to short-term enrichment by nitrate and phosphate. The first experiment, conducted just following ice-off, employed dark dilution culture to directly assess the impact of nutrients on bacterioplankton growth and consumption of terrigenous dissolved organic matter during snowmelt. The second experiment, conducted in transparent microcosms during autumn overturn, examined how bacterioplankton in unmanipulated microbial communities responded to nutrients concomitant with increasing phytoplankton-derived organic matter. In both experiments, phosphate enrichment (but not nitrate) caused significant increases in bacterioplankton growth, changed particulate organic stoichiometry, and induced shifts in bacterial community composition, including consistent declines in the relative abundance of Actinobacteria. The dark dilution culture showed a significant increase in dissolved organic carbon removal in response to phosphate enrichment. In transparent microcosms nutrient enrichment had no effect on concentrations of chlorophyll, carbon, or the fluorescence characteristics of dissolved organic matter, suggesting that bacterioplankton responses were independent of phytoplankton responses. These results demonstrate that bacterioplankton communities in unproductive high-elevation habitats can rapidly alter their taxonomic composition and metabolism in response to short-term phosphate enrichment. Our results reinforce the key role that phosphorus plays in oligotrophic lake ecosystems, clarify the nature of bacterioplankton nutrient limitation, and emphasize that evaluation of eutrophication in these habitats should incorporate heterotrophic microbial communities and processes

Metabolic syndrome, psychological status and quality of life in obesity: the QUOVADIS Study

Objective: We aimed to investigate the association of the clinical variables of the metabolic syndrome (MS) and psychological parameters on health-related quality of life (HRQL) in obesity. In particular, our aim was to investigate the relative impact of physical symptoms, somatic diseases and psychological distress on both the physical and the mental domains of HRQL. Design: Cross-sectional study. Subjects: A cohort of 1822 obese outpatients seeking treatment in medical centers. Measurements: HRQL was measured by the standardized summary scores for physical (PCS) and mental (MCS) components of the Short Form 36 Health Survey (SF-36). Patients were grouped according to tertiles of PCS and MCS. Metabolic and psychological profiles of PCS and MCS tertiles were compared by discriminant analysis. Results: The profile of metabolic and psychological variables was tertile-specific in 62.4 and 68.3% of patients in the lowest and highest tertiles of PCS, respectively, while concordance was low in the mid-tertile (32.8%). Concordance was very high in the lowest (74.4%) and in the highest (75.5%) tertiles of MCS, and was fair in the mid-tertile (53.2%). The main correlates of PCS were obesity-specific and general psychological well-being, BMI, body uneasiness, binge eating, gender and psychiatric distress. Only hypertension and hyperglycemia qualified as correlates among the components of MS. The components of MS did not define MCS. Conclusions: Psychological well-being is the most important correlate of HRQL in obesity, both in the physical and in the mental domains, whereas the features of MS correlate only to some extent with the physical domain of HRQL

3D tracking of extracellular vesicles by holographic fluorescence imaging

Fluorescence microscopy is the method of choice in biology for its molecular specificity and super-resolution capabilities. However, it is limited to a narrow z range around one observation plane. Here, we report an imaging approach that recovers the full electric field of fluorescent light with single-molecule sensitivity. We expand the principle of digital holography to fast fluorescent detection by eliminating the need for phase cycling and enable three-dimensional (3D) tracking of individual nanoparticles with an in-plane resolution of 15 nm and a z-range of 8 mm. As a proof-of-concept biological application, we image the 3D motion of extracellular vesicles (EVs) inside live cells. At short time scales (<4 s), we resolve near-isotropic 3D diffusion and directional transport. For longer lag times, we observe a transition toward anisotropic motion with the EVs being transported over long distances in the axial plane while being confined in the horizontal dimension.ISSN:2375-254

Novel signalling mechanisms and targets in renal ischaemia and reperfusion injury

Acute kidney injury (AKI) induced by ischaemia and reperfusion (I/R) injury is a common and severe clinical problem. Vascular dysfunction, immune system activation, and tubular epithelial cell injury contribute to functional and structural deterioration. The search for novel therapeutic interventions for I/R induced AKI is a dynamic area of experimental research. Pharmacologic targeting of injury mediators and corresponding intracellular signalling in endothelial cells, inflammatory cells and the injured tubular epithelium could provide new opportunities yet may also pose great translational challenge. Here, we focus on signalling mediators, their receptors and intracellular signalling pathways which bear potential to abrogate cellular processes involved in the pathogenesis of I/R induced AKI. Sphingosine 1 phosphate (S1P) and its respective receptors, cytochrome P450 (CYP450)-dependent vasoactive eicosanoids, NF-{kappa}B and protein kinase-C (PKC) related pathways are representatives of such "druggable" pleiotropic targets. For example pharmacologic agents targeting S1P and PKC isoforms are already in clinical use for treatment of autoimmune diseases and were previously subject of clinical trials in kidney transplantation where I/R induced AKI occurs as a common complication. We summarize recent in vitro and in vivo experimental studies using pharmacologic and genomic targeting and highlight some of the challenges to clinical application of these advances

Survival and activity of individual bioaugmentation strains

Successful application of bioaugmentation for enhanced degradation of environmental pollutants is often limited by the lack of methods to monitor the survival and activity of individual bioaugmentation strains. However, recent advancements in sequencing technologies and molecular techniques now allow us to address these limitations. Here a complementing set of general applicable molecular methods are presented that provides detailed information on the performance of individual bioaugmentation strains under in situ conditions. The approach involves genome sequencing to establish highly specific qPCR and RT-qPCR tools for cell enumerations and expression of involved genes, stable isotope probing to follow growth on the target compounds and GFP-tagging to visualize the bioaugmentation strains directly in samples, all in combination with removal studies of the target compounds. The concept of the approach is demonstrated through a case study involving degradation of aromatic hydrocarbons in activated sludge augmented with the bioaugmentation strain Pseudomonas monteilii SB3078

Predators and nutrient availability favor protozoa-resisting bacteria in aquatic systems

The long co-existence of bacteria and protozoa has led to the development of bacterial protozoa resistance strategies, which are suggested to serve as drivers for the evolution of pathogenic bacteria. However, the ecological mechanisms underpinning selection for protozoa-resistance in aquatic bacteria are poorly known. To assess the role of nutrient availability and predation-pressure on selection for protozoa-resisting bacteria (PRB), an enrichment-dilution experiment was designed using laboratory microcosms containing natural lake water. PRB was monitored by screening 16S rRNA amplicon sequence data for reads assigned to bacteria that previously has been shown to resist degradation by amoebae. To estimate the effects of the microbial food web dynamics (microscopy of; heterotrophic bacteria, phytoplankton, protozoa and rotifers) and physicochemical variables on the PRB abundance in the study system, a joint species distribution modelling approach was used. The predation-pressure (ratio between predator and bacterial biomass) had a positive effect on the abundance of the PRB genus Mycobacterium, while perturbation (enrichment and dilution) favored the PRB genus Pseudomonas that dominated the bacterial community in the disturbed systems. Our results show that PRB with different ecological strategies can be expected in water of high and intermediate nutrient levels and after major disturbances of an aquatic system