Bioreactor scalability: laboratory-scale bioreactor design influences performance, ecology, and community physiology in expanded granular sludge bed bioreactors

Studies investigating the feasibility of new, or improved, biotechnologies, such as wastewater treatment digesters, inevitably start with laboratory-scale trials. However, it is rarely determined whether laboratory-scale results reflect full-scale performance or microbial ecology. The Expanded Granular Sludge Bed (EGSB) bioreactor, which is a high-rate anaerobic digester configuration, was used as a model to address that knowledge gap in this study. Two laboratory-scale idealizations of the EGSB—a one-dimensional and a three- dimensional scale-down of a full-scale design—were built and operated in triplicate under near-identical conditions to a full-scale EGSB. The laboratory-scale bioreactors were seeded using biomass obtained from the full-scale bioreactor, and, spent water from the distillation of whisky from maize was applied as substrate at both scales. Over 70 days, bioreactor performance, microbial ecology, and microbial community physiology were monitored at various depths in the sludge-beds using 16S rRNA gene sequencing (V4 region), specific methanogenic activity (SMA) assays, and a range of physical and chemical monitoring methods. SMA assays indicated dominance of the hydrogenotrophic pathway at full-scale whilst a more balanced activity profile developed during the laboratory-scale trials. At each scale, Methanobacterium was the dominant methanogenic genus present. Bioreactor performance overall was better at laboratory-scale than full-scale. We observed that bioreactor design at laboratory-scale significantly influenced spatial distribution of microbial community physiology and taxonomy in the bioreactor sludge-bed, with 1-D bioreactor types promoting stratification of each. In the 1-D laboratory bioreactors, increased abundance of Firmicutes was associated with both granule position in the sludge bed and increased activity against acetate and ethanol as substrates. We further observed that stratification in the sludge-bed in 1-D laboratory-scale bioreactors was associated with increased richness in the underlying microbial community at species (OTU) level and improved overall performance

GABAB receptors regulate extrasynaptic GABAA receptors

Tonic inhibitory GABAA receptor-mediated currents are observed in numerous cell types in the CNS, including thalamocortical neurons of the ventrobasal thalamus, dentate gyrus granule cells, and cerebellar granule cells. Here we show that in rat brain slices, activation of postsynaptic GABAB receptors enhances the magnitude of the tonic GABAA current recorded in these cell types via a pathway involving Gi/o G proteins, adenylate cyclase, and cAMP-dependent protein kinase. Using a combination of pharmacology and knockout mice, we show that this pathway is independent of potassium channels or GABA transporters. Furthermore, the enhancement in tonic current is sufficient to significantly alter the excitability of thalamocortical neurons. These results demonstrate for the first time a postsynaptic crosstalk between GABAB and GABAA receptors.peer-reviewe

Stable encoding of visual cues in the mouse retrosplenial cortex

The rodent retrosplenial cortex (RSC) functions as an integrative hub for sensory and motor signals, serving roles in both navigation and memory. While RSC is reciprocally connected with the sensory cortex, the form in which sensory information is represented in the RSC and how it interacts with motor feedback is unclear and likely to be critical to computations involved in navigation such as path integration. Here, we used 2-photon cellular imaging of neural activity of putative excitatory (CaMKII expressing) and inhibitory (parvalbumin expressing) neurons to measure visual and locomotion evoked activity in RSC and compare it to primary visual cortex (V1). We observed stimulus position and orientation tuning, and a retinotopic organization. Locomotion modulation of activity of single neurons, both in darkness and light, was more pronounced in RSC than V1, and while locomotion modulation was strongest in RSC parvalbumin-positive neurons, visual-locomotion integration was found to be more supralinear in CaMKII neurons. Longitudinal measurements showed that response properties were stably maintained over many weeks. These data provide evidence for stable representations of visual cues in RSC that are spatially selective. These may provide sensory data to contribute to the formation of memories of spatial information

Drift dynamics in microbial communities and the effective community size

The structure and diversity of all open microbial communities are shaped by individual births, deaths, speciation and immigration events; the precise timings of these events are unknowable and unpredictable. This randomness is manifest as ecological drift in the population dynamics, the importance of which has been a source of debate for decades. There are theoretical reasons to suppose that drift would be imperceptible in large microbial communities, but this is at odds with circumstantial evidence that effects can be seen even in huge, complex communities. To resolve this dichotomy we need to observe dynamics in simple systems where key parameters, like migration, birth and death rates can be directly measured. We monitored the dynamics in the abundance of two genetically modified strains of Escherichia coli, with tuneable growth characteristics, that were mixed and continually fed into 10 identical chemostats. We demonstrated that the effects of demographic (non‐environmental) stochasticity are very apparent in the dynamics. However, they do not conform to the most parsimonious and commonly applied mathematical models, where each stochastic event is independent. For these simple models to reproduce the observed dynamics we need to invoke an “effective community size”, which is smaller than the census community size

North American wetlands and mosquito control

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in International Journal of Environmental Research and Public Health 9 (2012): 4537-4605, doi:10.3390/ijerph9124537.Wetlands are valuable habitats that provide important social, economic, and ecological services such as flood control, water quality improvement, carbon sequestration, pollutant removal, and primary/secondary production export to terrestrial and aquatic food chains. There is disagreement about the need for mosquito control in wetlands and about the techniques utilized for mosquito abatement and their impacts upon wetlands ecosystems. Mosquito control in wetlands is a complex issue influenced by numerous factors, including many hard to quantify elements such as human perceptions, cultural predispositions, and political climate. In spite of considerable progress during the last decades, habitat protection and environmentally sound habitat management still remain inextricably tied to politics and economics. Furthermore, the connections are often complex, and occur at several levels, ranging from local businesses and politicians, to national governments and multinational institutions. Education is the key to lasting wetlands conservation. Integrated mosquito abatement strategies incorporate many approaches and practicable options, as described herein, and need to be well-defined, effective, and ecologically and economically sound for the wetland type and for the mosquito species of concern. The approach will certainly differ in response to disease outbreaks caused by mosquito-vectored pathogens versus quality of life issues caused by nuisance-biting mosquitoes. In this contribution, we provide an overview of the ecological setting and context for mosquito control in wetlands, present pertinent information on wetlands mosquitoes, review the mosquito abatement options available for current wetlands managers and mosquito control professionals, and outline some necessary considerations when devising mosquito control strategies. Although the emphasis is on North American wetlands, most of the material is applicable to wetlands everywhere.Publication of this article was funded in part by the University of Florida Open Access Publishing Fund

Characterization of LP-Z Lipoprotein Particles and Quantification in Subjects with Liver Disease Using a Newly Developed NMR-Based Assay

Background: Lipoprotein particles with abnormal compositions, such as lipoprotein X (LP-X) and lipoprotein Z (LP-Z), have been described in cases of obstructive jaundice and cholestasis. The study objectives were to: (1) develop an NMR-based assay for quantification of plasma/serum LP-Z particles, (2) evaluate the assay performance, (3) isolate LP-Z particles and characterize them by lipidomic and proteomic analysis, and (4) quantify LP-Z in subjects with various liver diseases. Methods: Assay performance was assessed for linearity, sensitivity, and precision. Mass spectroscopy was used to characterize the protein and lipid content of isolated LP-Z particles. Results: The assay showed good linearity and precision (2.5-6.3%). Lipid analyses revealed that LP-Z particles exhibit lower cholesteryl esters and higher free cholesterol, bile acids, acylcarnitines, diacylglycerides, dihexosylceramides, lysophosphatidylcholines, phosphatidylcholines, triacylglycerides, and fatty acids than low-density lipoprotein (LDL) particles. A proteomic analysis revealed that LP-Z have one copy of apolipoprotein B per particle such as LDL, but less apolipoprotein (apo)A-I, apoC3, apoA-IV and apoC2 and more complement C3. LP-Z were not detected in healthy volunteers or subjects with primary biliary cholangitis, primary sclerosing cholangitis, autoimmune hepatitis, or type 2 diabetes. LP-Z were detected in some, but not all, subjects with hypertriglyceridemia, and were high in some subjects with alcoholic liver disease. Conclusions: LP-Z differ significantly in their lipid and protein content from LDL. Further studies are needed to fully understand the pathophysiological reason for the enhanced presence of LP-Z particles in patients with cholestasis and alcoholic liver disease

Creatine and creatinine quantified using nuclear magnetic resonance:A method validation study and clinical associations between circulating creatine and fatigue in kidney transplant recipients

Background: A potential contributor to fatigue in kidney transplant recipients (KTR) may be impaired creatine homeostasis. We developed and validated a high-throughput NMR assay allowing for simultaneous measurement of circulating creatine and creatinine, and determined plasma creatine and estimated intramuscular creatine concentrations in KTRs, delineated their determinants and explored their associations with self-reported fatigue.Methods: An NMR assay was developed and validated for measurement of circulating creatinine and creatine concentrations. Plasma creatine and creatinine concentrations were measured in 618 KTR. Fatigue was assessed using the checklist individual strength. Associations of creatine parameters with fatigue was assessed using linear mixed effect models.Results: The NMR-based assay had good sensitivity, precision and demonstrated linearity across a large range of values. Among KTR, the mean age was 56 ± 13 years, 62% were men and eGFR was 54 ± 18 ml/min/1.73 m2. Plasma creatine concentration was 27 [19–39] µmol/L. Estimated intramuscular creatine concentration was 27 ± 7 mmol/kg. Higher plasma creatine concentration and higher estimated intramuscular creatine concentration were independently associated with a lower total fatigue score and less motivation problems.Conclusion: An NMR method for measurement of circulating creatine and creatinine which offers the potential for accurate and efficient quantification was developed. The found associations suggest that improving creatine status may play a beneficial role in mitigating fatigue.</p