Linking structure and function of microbial communities responsible for sedimentary nitrogen processes in North Carolina estuaries

Estuaries and coastal areas are highly diverse and productive ecosystems that serve as critical habitats for many marine organisms. Anthropogenic activities and changes in coastal land use have resulted in nutrient over-enrichment, posing a threat to the ecological integrity of estuaries. Nitrogen is often the limiting nutrient and its dynamics are central in determining coastal ecosystem health. The cycling and removal of nitrogen is primarily microbially mediated and the structure of these microbial communities is tightly interlaced with ecosystem function. Recycling processes nitrification and dissimilatory nitrate reduction to ammonium (DNRA) serve as a conduit for loss when coupled to the removal processes of denitrification and anaerobic ammonium oxidation (anammox). These processes occur simultaneously in estuarine sediments and are influenced by a suite of environmental factors. Understanding these interactions within the complex microbial communities, how microbial community structure responds to environmental changes, and how this relates to ecosystem function is a challenging but important goal in microbial ecology and particularly relevant in today\u27s changing world, as climate change and sea level rise are eminent threats to coastal ecosystems. This study identified geomorphological, hydrological, and biogeochemical features, including water residence time, sediment %organics, nutrient availability, salinity, and hydrogen sulfide, that are important in controlling the community structures of nitrogen cycling microbes and their activities. Quantitative criteria were established to identify and assess the role of nitrogen removal hotspots in estuarine sediments. Specific groups of denitrifying and anammox bacteria with a higher nitrogen removal capacity were identified, suggesting the community composition is important in ecosystem function. Additionally, niche differentiation of nitrifying microbes was unveiled by linking their physiology to specific environmental parameters. Examination of microbial community structure and its response to environmental conditions combined with measurements of biogeochemical rates enabled the linkage of nitrogen cycling members with particular functions, a theme addressed throughout this dissertation

Provoking Punches: Factors Influencing Perceived Violent Reactions to Negative Situations

Purpose: Violence among college students is an important area of research as this group is at an increased risk of both engaging in and being a victim of violence. As such, the current research aimed to examine factors that may influence violent tendencies among a sample of college students. Method: Data from 101 completed surveys were analyzed. Principal components factor analysis and Cronbach’s alpha resulted in the creation of six independent variables (gun experience, weapons support, anger contagion, witness violence, violent community, and aggressive beliefs) and four dependent variables (competition for resources, social attacks, physical attacks, and unfair situations). OLS regression was used to estimate the impact of each variable on perceptions of reacting with violence to four negative situations. Results: Gun experience and violent community significantly predicted responding violently to both social and physical attacks, while gun support was only predictive of violence in competition for resources. Additionally, aggressive beliefs predicted perceptions of violent responses to physical attacks and in unfair situations. Finally, anger contagion was associated with students reporting an increased likelihood of responding violently to social attacks. Conclusions: While research shows the importance of understanding violence exposure and aggressive norms in creating and improving violence prevention programs and anti-violence strategies, the role that perceptions play is largely absent. Furthermore, this research supports the importance of implementing these programs and strategies among college students/young adults to potentially reduce violence and aggression within this age group

Linking DNRA community structure and activity in a shallow lagoonal estuarine system

Dissimilatory nitrate reduction to ammonium (DNRA) and denitrification are two nitrate respiration pathways in the microbial nitrogen cycle. Diversity and abundance of denitrifying bacteria have been extensively examined in various ecosystems. However, studies on DNRA bacterial diversity are limited, and the linkage between the structure and activity of DNRA communities has yet to be discovered. We examined the composition, diversity, abundance, and activities of DNRA communities at five sites along a salinity gradient in the New River Estuary, North Carolina, USA, a shallow temporal/lagoonal estuarine system. Sediment slurry incubation experiments with N-15-nitrate were conducted to measure potential DNRA rates, while the abundance of DNRA communities was calculated using quantitative PCR of nrfA genes encoding cytochrome C nitrite reductase, commonly found in DNRA bacteria. A pyrosequencing method targeting nrfA genes was developed using an Ion Torrent sequencer to examine the diversity and composition of DNRA communities within the estuarine sediment community. We found higher levels of nrfA gene abundance and DNRA activities in sediments with higher percent organic content. Pyrosequencing analysis of nrfA genes revealed spatial variation of DNRA communities along the salinity gradient of the New River Estuary. Percent abundance of dominant populations was found to have significant influence on overall activities of DNRA communities. Abundance of dominant DNRA bacteria and organic carbon availability are important regulators of DNRA activities in the eutrophic New River Estuary

Dimensional Changes of Upper Airway after Rapid Maxillary Expansion: A Prospective Cone-beam Computed Tomography Study

Introduction: The aim of this prospective study was to use cone-beam computed tomography to assess the dimensional changes of the upper airway in orthodontic patients with maxillary constriction treated by rapid maxillary expansion. Methods: Fourteen orthodontic patients (mean age, 12.9 years; range, 9.7-16 years) were recruited. The patients with posterior crossbite and constricted maxilla were treated with rapid maxillary expansion as the initial part of their comprehensive orthodontic treatments. Before and after rapid maxillary expansion conebeam computed tomography scans were taken to measure the retropalatal and retroglossal airway changes in terms of volume, and sagittal and cross-sectional areas. The transverse expansions by rapid maxillary expansion were assessed between the midlingual alveolar bone plates at the maxillary first molar and first premolar levels. The measurements of the before and after rapid maxillary expansion scans were compared by using paired t tests with the Bonferroni adjustment for multiple comparisons. Results: After rapid maxillary expansion, significant and equal amounts of 4.8 mm of expansion were observed at the first molar (P 5 0.0000) and the first premolar (P 5 0.0000) levels. The width increase at the first premolar level (20.0%) was significantly greater than that at the first molar level (15.0%) (P 5 0.035). As the primary outcome variable, the cross-sectional airway measured from the posterior nasal spine to basion level was the only parameter showing a significant increase of 99.4 mm2 (59.6%) after rapid maxillary expansion (P 5 0.0004). Conclusions: These results confirm the findings of previous studies of the effect of rapid maxillary expansion on the maxilla. Additionally, we found that only the cross-sectional area of the upper airway at the posterior nasal spine to basion level significantly gains a moderate increase after rapid maxillary expansion

Mono- and Trivalent Ions around DNA: A Small-Angle Scattering Study of Competition and Interactions

The presence of small numbers of multivalent ions in DNA-containing solutions results in strong attractive forces between DNA strands. Despite the biological importance of this interaction, e.g., DNA condensation, its physical origin remains elusive.Wecarried out a series of experiments to probe interactions between short DNA strands as small numbers of trivalent ions are included in a solution containing DNA and monovalent ions. Using resonant (anomalous) and nonresonant small angle x-ray scattering, we coordinated measurements of the number and distribution of each ion species around the DNA with the onset of attractive forces between DNA strands. DNA-DNA interactions occur as the number of trivalent ions increases. Surprisingly good agreement is found between data and size-corrected numerical Poisson-Boltzmann predictions of ion competition for non- and weakly interacting DNAs. We also obtained an estimate for the minimum number of trivalent ions needed to initiate DNA-DNA attraction

Comparison of Nitrogen Oxide Metabolism among Diverse Ammonia-Oxidizing Bacteria

Ammonia-oxidizing bacteria (AOB) have well characterized genes that encode and express nitrite reductases (NIR) and nitric oxide reductases (NOR). However, the connection between presence or absence of these and other genes for nitrogen transformations with the physiological production of nitric oxide (NO) and nitrous oxide (N2O) has not been tested across AOB isolated from various trophic states, with diverse phylogeny, and with closed genomes. It is therefore unclear if genomic content for nitrogen oxide metabolism is predictive of net N2O production. Instantaneous microrespirometry experiments were utilized to measure NO and N2O emitted by AOB during active oxidation of ammonia (NH3) or hydroxylamine (NH2OH) and through a period of anoxia. This data was used in concert with genomic content and phylogeny to assess whether taxonomic factors were predictive of nitrogen oxide metabolism. Results showed that two oligotrophic AOB strains lacking annotated NOR-encoding genes released large quantities of NO and produced N2O abiologically at the onset of anoxia following NH3-oxidation. Furthermore, high concentrations of N2O were measured during active O2-dependent NH2OH oxidation by the two oligotrophic AOB in contrast to non-oligotrophic strains that only produced N2O at the onset of anoxia. Therefore, complete nitrifier denitrification did not occur in the two oligotrophic strains, but did occur in meso- and eutrophic strains, even in Nitrosomonas communis Nm2 that lacks an annotated NIR-encoding gene. Regardless of mechanism, all AOB strains produced measureable N2O under tested conditions. This work further confirms that AOB require NOR activity to enzymatically reduce NO to N2O in the nitrifier denitrification pathway, and also that abiotic reactions play an important role in N2O formation, in oligotrophic AOB lacking NOR activity

The organization of conspecific face space in nonhuman primates

Humans and chimpanzees demonstrate numerous cognitive specializations for processing faces, but comparative studies with monkeys suggest that these may be the result of recent evolutionary adaptations. The present study utilized the novel approach of face space, a powerful theoretical framework used to understand the representation of face identity in humans, to further explore species differences in face processing. According to the theory, faces are represented by vectors in a multidimensional space, the centre of which is defined by an average face. Each dimension codes features important for describing a face's identity, and vector length codes the feature's distinctiveness. Chimpanzees and rhesus monkeys discriminated male and female conspecifics' faces, rated by humans for their distinctiveness, using a computerized task. Multidimensional scaling analyses showed that the organization of face space was similar between humans and chimpanzees. Distinctive faces had the longest vectors and were the easiest for chimpanzees to discriminate. In contrast, distinctiveness did not correlate with the performance of rhesus monkeys. The feature dimensions for each species' face space were visualized and described using morphing techniques. These results confirm species differences in the perceptual representation of conspecific faces, which are discussed within an evolutionary framework

In the Face of Anti-LGBQ Behaviour: Saskatchewan High-school Students' Perceptions of School Climate and Consequential Impact

In Canada, there is a dearth of research on school climate for lesbian, gay, bisexual, and questioning (LGBQ) students. Using social networking, sixty students from high-schools in Saskatchewan participated in a climate survey. Results indicated that anti-LGBQ speech is widespread, as were other forms of harassment. The more victimization that was reported by students known, or perceived to be, LGBQ, the more deleterious were the consequences for their academic performance, social lives, participation in sports and extra-curricular activities, and overall enjoyment of school. Limitations associated with the study and directions for future research are detailed.