Effect of Tidal Cycling Rate on the Distribution and Abundance of Nitrogen-Oxidizing Bacteria in a Bench-Scale Fill-and-Drain Bioreactor

Most domestic wastewater can be effectively treated for secondary uses by engineered biological systems. These systems rely on microbial activity to reduce nitrogen (N) content of the reclaimed water. Such systems often employ a tidal-flow process to minimize space requirements for the coupling of aerobic and anaerobic metabolic processes. In this study, laboratory-scale tidal-flow treatment systems were studied to determine how the frequency and duration of tidal cycling may impact reactor performance. Fluorescent in situ hybridization and epifluorescence microscopy were used to enumerate the key functional groups of bacteria responsible for nitrification and anaerobic ammonium oxidation (anammox), and N-removal efficiency was calculated via a mass-balance approach. When water was cycled (i.e., reactors were filled and drained) at high frequencies (16–24 cycles day−1), nitrate accumulated in the columns—presumably due to inadequate periods of anoxia that limited denitrification. At lower frequencies, such as 4 cycles day−1, nearly complete N removal was achieved (80–90%). These fill-and-drain systems enriched heavily for nitrifiers, with relatively few anammox-capable organisms. The microbial community produced was robust, surviving well through short (up to 3 h) anaerobic periods and frequent system-wide perturbation

Examining the Relationship Between Confusion and Learning: A Descriptive Meta-Analysis

Previous research into confusion and learning neglects to investigate how this relationship varies when faced with impact factors such as multiple types of affect and learning measurements, learning environment, or grade level. Moreover, past research also reports di-verse effect size values for this relationship, making the correlation ambiguous. As such, the current research seeks to reconcile these nuances between confusion and learning through a meta-analytic approach. In this analysis, it was found that there was no relationship between confusion and learning gains, or in the subgroup analysis of grade level. Since only one impact factor, grade level, was analyzed, it is considered that the analysis of other or multiple impact factors could help to further understand the association between confusion and learning. It is also reasoned that variability in the definitions of confusion and learning in the papers included in the meta-analysis as well as publication bias contribute to this result. As such, future research may choose to investigate these avenues and continued research generally into the association between confusion and learning would also be helpful to better understand this relationship

An approach for collection of nearfield groundwater samples in submerged limestone caverns

Walls of submerged caves feeding Florida springs are often lined with a heavy mat of filamentous bacteria, many of which are able to oxidize reduced sulfur in groundwater migrating from the porous bedrock into the cave conduit. To determine changes in water chemistry as water passes through the microbial mat, a simple device made from standard well screen and sealed with a rubber stopper and controllable vents was installed in a hole drilled in the wall of the cave passage. The sampler was sealed in place with marine epoxy. We measured anions in water from the sampler and from the water-filled conduit taken just outside the sampler. Most anions measured viz., Cl−, NO3−, and PO43−, increased slightly between the matrix and conduit waters. However, traces of sulfide were measured in the water from the rock matrix, but not in the conduit. SO42− concentrations in the conduit were about twice that measured in the water from the sampler, about 22 and 11 mg SO42− L−1, respectively, providing further evidence that sulfur oxidation is an important process in the bacterial mats attached to the limestone surfaces in these caves. An additional use of the sampling device is to measure discharge from the local bedrock into the cave conduit.Keywords: sulfur oxidation, bacteria, acid dissolution, groundwater chemistry.DOI:10.3986/ac.v42i2-3.664

Biological Control on Acid Generation at the Conduit-Bedrock Boundary in Submerged Caves: Quantification through Geochemical Modeling

No-mount Cave, located in Wekiwa Springs State Park in central Florida, USA, is an aphotic, submerged, freshwater cave in which large colonies of sulfur-oxidizing bacteria live in filamentous microbial mats. Upwardly discharging groundwater enters the cave from the Upper Floridan aquifer, specifically the Eocene-aged Ocala Limestone. We undertook a combined field, laboratory, and modeling study in which we sought to determine the amount of calcite dissolution attributable to the generation of protons by microbially mediated sulfide oxidation. The chemical compositions of groundwater within the limestone formation collected through a newly designed sampling device and of water in the cave conduit were used in geochemical modeling. We used the reaction-path model PHREEQCI to quantify the amount of calcite dissolution expected under various plausible scenarios for mixing of formation water with conduit water and extent of bacterial sulfide oxidation. Laboratory experiments were conducted using flow-through columns packed with crushed limestone from the study site. Replicate columns were eluted with artificial groundwater containing dissolved HS- in the absence of microbial growth. Without biologically mediated sulfide oxidation, no measurable calcite dissolution occurred in laboratory experiments and no additional amount of speleogenesis is expected as formation water mixes with conduit water in the field. In contrast, significant calcite dissolution is driven by the protons released in the biological transformation of the aqueous sulfur species. Although a range of results were calculated, a plausible amount of 158 mg Ca2+ released to conduit water per liter of groundwater crossing the formation-conduit boundary and mixing with an equal volume of conduit water was predicted. Our modeling results indicate that significant cave development can be driven by microbially mediated sulfide oxidation under these hydrogeochemical conditions.žKeywords: calcite dissolution, microbial sulfide oxidation, geochemical model.DOI: 10.3986/ac.v42i2-3.66

Final technical report: The effect of physical and chemical heterogeneities in a porous medium on the transport of bacteria

Among the demonstrated processes influencing the transport of bacteria through aquifers, the deposition of cells on mineral surfaces is one of the most important. Heterogeneous distribution of aquifer properties such as mineral-grain oxide coatings and preferred flow paths can control the numbers of microbes arriving a point down gradient from their injection, and these properties can also affect the distribution of the organisms remaining in the sedimentary matrix. The distribution of metal oxide coatings affects the final location of retained cells within the matrix but had no effect on total breakthrough of applied bacteria. We were able to demonstrate transverse mixing of both conservative tracers and bacteria between regions of differing hydraulic conductivity; the conservative tracer could be used to model the transverse mixing of the bacteria. We were able to show that the presence of metal oxide coatings on aquifer surfaces retarded a reactive tracer (SO{sub 4}{sup 2-}) that simulated bacterial retardation in the laboratory. When metal oxide coatings were absent (due to bacterial establishment of a reducing environment) the tracer and bacteria were not retarded. The effect was reproduced in a tracer experiment done in the field. The results suggest that bacterial transport in the subsurface is controlled by a number of interrelated and confounding factors that prevent accurate prediction of transport given the present state of knowledge

Clinical impairment in premanifest and early Huntington's disease is associated with regionally specific atrophy.

TRACK-HD is a multicentre longitudinal observational study investigating the use of clinical assessments and 3-Tesla magnetic resonance imaging as potential biomarkers for future therapeutic trials in Huntington's disease (HD). The cross-sectional data from this large well-characterized dataset provide the opportunity to improve our knowledge of how the underlying neuropathology of HD may contribute to the clinical manifestations of the disease across the spectrum of premanifest (PreHD) and early HD. Two hundred and thirty nine gene-positive subjects (120 PreHD and 119 early HD) from the TRACK-HD study were included. Using voxel-based morphometry (VBM), grey and white matter volumes were correlated with performance in four domains: quantitative motor (tongue force, metronome tapping, and gait); oculomotor [anti-saccade error rate (ASE)]; cognition (negative emotion recognition, spot the change and the University of Pennsylvania smell identification test) and neuropsychiatric measures (apathy, affect and irritability). After adjusting for estimated disease severity, regionally specific associations between structural loss and task performance were found (familywise error corrected, P < 0.05); impairment in tongue force, metronome tapping and ASE were all associated with striatal loss. Additionally, tongue force deficits and ASE were associated with volume reduction in the occipital lobe. Impaired recognition of negative emotions was associated with volumetric reductions in the precuneus and cuneus. Our study reveals specific associations between atrophy and decline in a range of clinical modalities, demonstrating the utility of VBM correlation analysis for investigating these relationships in HD

Mapping Copy Number Variation by Population Scale Genome Sequencing

Genomic structural variants (SVs) are abundant in humans, differing from other forms of variation in extent, origin and functional impact. Despite progress in SV characterization, the nucleotide resolution architecture of most SVs remains unknown. We constructed a map of unbalanced SVs (that is, copy number variants) based on whole genome DNA sequencing data from 185 human genomes, integrating evidence from complementary SV discovery approaches with extensive experimental validations. Our map encompassed 22,025 deletions and 6,000 additional SVs, including insertions and tandem duplications. Most SVs (53%) were mapped to nucleotide resolution, which facilitated analysing their origin and functional impact. We examined numerous whole and partial gene deletions with a genotyping approach and observed a depletion of gene disruptions amongst high frequency deletions. Furthermore, we observed differences in the size spectra of SVs originating from distinct formation mechanisms, and constructed a map of SV hotspots formed by common mechanisms. Our analytical framework and SV map serves as a resource for sequencing-based association studies.Organismic and Evolutionary Biolog