Increasing evidence suggests that the oral microbiome is highly relevant to cardiometabolic outcomes. Associations between the oral microbiome and extra-oral outcomes are most commonly hypothesized to result from a chronic inflammatory response to a dysbiotic oral microbiome. However, an alternative mechanism hypothesized to link the oral microbiome to cardiometabolic risk is via the production of nitric oxide, a physiologically important gaseous transmitter. The enterosalivary nitrate-nitrite-nitric oxide pathway of nitric oxide generation is dependent on the presence of nitrate-reducing oral bacteria in the mouth to reduce salivary nitrates to nitrite, which are then swallowed and made systemically bioavailable for further reduction into nitric oxide in the blood vessels and tissues. Thus, this pathway presents a mechanism for oral bacteria to exert a beneficial influence on cardiometabolic health. The overall objective of this dissertation is to advance the understanding of the role of nitrate-reducing oral bacteria in cardiometabolic outcomes in a population setting. This objective was met using three aims. First, a systematic literature review was conducted to identify and assess the associations between nitrate-reducing oral bacteria and insulin resistance, plasma glucose, diabetes, blood pressure and hypertension found in the existing literature. The literature review found no study that explicitly tested the hypothesis of an association between nitrate-reducing oral bacteria and the cardiometabolic outcomes of interest. In addition, there were very few observed associations between nitrate-reducing oral bacteria and these cardiometabolic outcomes, and the findings were inconsistent across studies. Secondly, the associations between nitrate-reducing oral bacteria and insulin resistance, plasma glucose, blood pressure, prediabetes and hypertension were assessed using baseline data from a cohort of diabetes-free participants. Increased levels of oral nitrate-reducing bacteria were associated with lower insulin resistance, plasma glucose and mean systolic blood pressure cross-sectionally, but no associations were found with prediabetes and hypertension. Finally, as dietary nitrate intake influences the level of salivary nitrate in the mouth for the nitrate-reducing oral bacteria to act on, the associations between dietary nitrate and insulin resistance, plasma glucose, blood pressure, prediabetes and hypertension were assessed. No clear associations between higher dietary nitrate intake and the cardiometabolic outcomes were found. However, there was some indication that higher dietary nitrate intake was associated with lower systolic blood pressure. The interaction of dietary nitrate intake with nitrate-reducing oral bacteria was then considered, but no evidence of such interaction was found. Overall, the results of this dissertation suggest that higher levels of nitrate-reducing oral bacteria may confer health benefits across the range of bacterial levels likely observed in human populations. These findings help inform future public health research aimed at utilizing the enterosalivary pathway of nitric oxide generation to improve cardiometabolic health.

Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (leaves: 120-121)

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 53-62). Also available on the World Wide Web.

With ever increasing regulation of the quality of drinking water and wastewater treatment, there is a need to develop methods to remove nitrogenous compounds from water. These processes are mediated by a variety of micro-organisms that can oxidise ammonia to nitrate, and then reduced to gaseous nitrogen by another set of organisms. This two stage process involves the relatively slow oxidation of ammonia to nitrate followed a relatively fast reduction of nitrate to nitrogen. Nitrate reduction normally requires anaerobic environments and the addition of organic matter to provide reducing power (electrons) for nitrate reduction. In practical situations the nitrate reduction can be problematic in those precise quantities of organic matter to ensure that the process occurs while not leaving residual organic matter. The aim of this study was to investigate microbial denitrification using electrochemical sources to replace organic matter as a redactant. The work also involved developing a system that could be optimised for nitrate removal in applied situations such as water processing in fish farming or drinking water, where high nitrate levels represent a potential health problem. Consequently, the study examined a range of developments for the removal of nitrate from water based on the development of electrochemical biotransformation systems for nitrate removal. This also offers considerable scope for the potential application of these systems in broader bio-nanotechnology based processes (particularly in bioremediation). The first stage of the study was to investigate the complex interactions between medium parameters and their effects on the bacterial growth rates. The results proved that acetate is a good carbon source for bacterial growth, and therefore it was used as an organic substrate for the biological process. High nitrate removal rate of almost 87% was successfully achieved by using a microbial fuel cell (MFC) enriched with soil inocula with the cathodes cells fed with nitrate and the anode fed with acetate. The maximum power density obtained was 1.26 mW/m2 at a current density of 10.23 mA/m2. The effects of acetate, nitrate and external resistance on current generation and denitrification activity were investigated, and the results demonstrated that nitrate removal was greatly dependent on the magnitude of current production within the MFC. Increase of acetate (anode) and nitrate (cathode) concentrations improved the process, while increasing external resistance reduced the activity. Furthermore, for a clear understanding of the nitrate reduction process, the analysis of the associated bacteria was performed through biochemical tests and examination of morphological characteristics. A diversity of nitrate reducing bacteria was observed; however a few were able to deliver complete denitrification. Pure cultures in MFC were examined and the voltage output achieved was about 36% of that obtained by mixed cultures. The nitrate removal gained was 56.2%, and this is almost 31% lower than that obtained by the mixed bacterial experiment. In an attempt to improve the MFC, modifications to the electrochemical properties of the electrode were investigated through the use of a cyclic voltammetry using carbon nanomaterials to coat the graphite felts electrodes. Among all the nanomaterials used in this study, graphitised carbon nanofibres (GCNFs) was selected for further investigation as it offered the best electrochemical performance and was thought to provide the largest active surface area. The performance of the MFC system coupled with the GCNFs modified electrodes was evaluated and significant improvements were observed. The highest voltage output achieved was about 41 mV with over 95% nitrate removal. The work is discussed in the context of improved MFC performance, potential analytic applications and further innovations using a bio-nanotechnology approach to analyse cell-electrode interactions.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Anthropogenic activities that utilise cyanide in various chemical forms have resulted in the disposal of cyanide-contaminated effluents into drainage systems that ultimately reach wastewater treatment plants (WWTP), without prior treatment. Cyanides (CN) and soluble salts could potentially inhibit biological processes in WWTP, which are responsible for the removal of contaminants from incoming wastewaters. The removal of nitrogenous compounds from such waters in processes such as nitrification and denitrification is among the core biological processes used to treat wastewaters in WWTP. Electroplating and mining industries are among the perpetrators of cyanide contamination of WWTP. The presence of these hazardous contaminants results in the alteration of metabolic functions of the microbial populations that are utilised in WWTP, thus rendering the wastewater treatment process ineffective. In this study, bacterial isolates that were able to carry out nitrification and aerobic denitrification under high salinity cyanogenic conditions were isolated from poultry slaughterhouse effluent. These strains were referred to as I, H and G. The isolated bacterial species were found to be able to oxidise ammonium nitrogen (NH4-N) in the presence of free cyanide (CN-) under halophilic conditions. Isolates I, H and G were identified using the 16S rDNA gene and were identified to be Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Furthermore, Response Surface Methodology was used to optimise the physicochemical conditions suitable for the proliferation of the isolates for free-cyanide degradation, nitrification and aerobic denitrification.

A elevada concentração de cloro das bifenilas policloradas provoca alta toxicidade do composto, o qual dificulta sua biodegradação. A contaminação de PCB no Brasil foi confirmada em estudo realizado na Bahia de Santos-São Vicente (São Paulo), o qual revelou a necessidade de um plano de ação para o controle e remoção de PCB no Brasil. Pretendeu-se assim, na realização da presente pesquisa, verificar quatro hipóteses: (1) A técnica de Microextração em fase sólida é uma metodologia eficaz para avaliação de bifenilas policloradas de amostras de reatores; (2) A condição fermentativa-metanogênica abriga comunidade resistente ao PCB, e removê-lo; (3) A condição desnitrificante abriga comunidade resistente ao PCB, e removê-lo e (4) A remoção de PCB, bem como, a composição microbiana é distinta em cada condição metabólica. Para tanto, reatores em batelada foram montados separadamente com biomassa anaeróbia proveniente de reator UASB usado no tratamento de água residuária de avicultura e biomassa de sistemas de lodos ativados de tratamento de esgoto sanitário. Os reatores operados em condição mesófila foram alimentados com meio sintético, co-substratos, sendo etanol (457 mg.L-1) e formiato de sódio (680 mg.L-1) para os reatores anaeróbios, e somente etanol (598 mg.L-1) para os reatores anóxicos, além de PCB padrão Sigma (congêneres PCBs 10, 28, 52, 153, 138 e 180) em diferentes concentrações, dependendo do objetivo do ensaio. A aplicação do método de extração por SPME com análise em cromatógrafo gasoso com detector por captura de elétrons foi adequada para a determinação dos seis congêneres de PCB. Obteve-se ampla faixa de linearidade, seletividade frente aos vários interferentes, além da robustez do método, utilidade e confiabilidade na identificação e quantificação específica dos seis congêneres de PCB. A Hipótese 1 foi aceita; ou seja, por meio da aplicação da metodologia SPME foi possível quantificar os PCB nos reatores em batelada. Apesar de ter sido comprovada a inibição metanogênica na presença de PCB, com IC50 de 0,03 mg.L<sup-1 (concentração na qual 50&#37; da atividade metanogênica é inibida), a partir da análise dos reatores metanogênicos no Ensaio de Remoção, foi confirmada a remoção de 0,92 mg.L-1, 0,19 mg.L-1, 0,18 mg.L-1, 0,07 mg.L-1, 0,55 mg.L-1 e 0,47 mg.L-1 para os PCBs 10, 28, 52, 153, 138 e 180, respectivamente, para 1,5 mg.L-1 inicial. Thermotogaceae, Sedimentibacter, Anaerolinaceae e Pseudomonas, foram identificadas nos reatores anaeróbios por meio da plataforma Illumina. Representantes de Thermotogaceae e Sedimentibacter foram identificados em sistemas com elevada taxa de remoção de PCB, e representantes do filo Chloroflexi (grupo no qual representantes da Anaerolineae estão inseridos) foram os primeiros microrganismos desalogenadores de PCB identificados. Assim a Hipótese 2 foi aceita; ou seja, por meio de ensaios em batelada foi comprovada a toxicidade do PCB sobre a comunidade anaeróbia, a alteração da composição microbiana influenciada pela presença de PCB e a remoção nesta condição. Verificou-se ainda que na presença de PCB ocorreu a desnitrificação e comparando-se diferentes relações C/N-NO3-, foi estipulado a relação 6,95 como ideal na presença de PCB. Mesmo sendo confirmada a inibição da comunidade anóxica na presença de PCB com IC50 de 1,0 mg.L-1, verificou-se remoção de 1,02 mg.L-1, 0,85 mg.L-1, 1,31 mg.L-1, 1,02 mg.L-1, 0,03 mg.L-1, e 0,09 mg.L-1, para os PCBs 10, 28, 52, 153, 138 e 180, respectivamente, para 1,5 mg.L-1, inicial. Bactérias semelhantes a Aeromonadaceae, Lutispora, Sedimentibacter e Thermotogaceae foram identificadas nos reatores desnitrificantes. Representantes de Aeromonadaceae e Lutispora estão relacionados com o metabolismo desnitrificante e representantes de Thermotogaceae e Sedimentibacter foram identificados em sistemas com elevada taxa de remoção de PCB. A Hipótese 3 foi também aceita; ou seja, por meio de ensaios em batelada foi calculada a relação C/N-NO3- ideal na presença de PCB e foi comprovada a toxicidade do PCB sobre a comunidade anóxica, a alteração da composição microbiana influenciada pela presença de PCB e a remoção nesta condição. A maior remoção de PCB foi verificada para a condição anaeróbia (entre 45&#37; a 100&#37;), quando comparada com a condição anóxica (entre 10&#37; a 95&#37;). Bactérias semelhantes a Sedimentibacter e pertencentes a família Thermotogaceae foram identificadas nas duas condições nutricionais. Entretanto, mesmo verificando-se elevada abundancia relativa desses grupos nos reatores, evidenciou-se distinção entre as biomassas em cada condição. Assim, a Hipótese 4 foi aceita; ou seja, por meio de ensaios em batelada foi comprovada maior eficiência de remoção sob condição anaeróbia e distinta composição microbiana em cada condição. / The high chlorine concentration in polychlorinated biphenyls improves its toxicity, complicating their biodegradation. A study conducted in Santos-São Vicente Bay (São Paulo) confirmed the PCB contamination in Brazil and reveled the need of an action plan to control e remove the PCB in Brazil. In this sense the aim of this study was to evaluate four hypotheses: (1) The Solid Phase Micro Extraction is an efficient methodology to evaluate biphenyl polychlorinated in reactors; (2) The fermentative-methanogenic microorganisms are resistant to PCB and capable to consume it; (3) The denitrifying microorganisms are resilient to the PCB and capable to remove it; (4) The PCB removal, as well the microbial composition is distinct in each condition. Therefore, batch reactors were operated separately inoculated with anaerobic biomass from UASB reactor treating poultry wastewater and biomass from activated sludge treating sewage wastewater. The reactors were feed with synthetic medium, co-substrates, as ethanol (457 mg.L-1) and sodium formate (680 mg.L-1) for the anaerobic reactors, and ethanol (598 mg.L-1) for the anoxic reactors and different concentrations of six congeners of PCB (PCBs 10, 28, 52, 153, 138 and 180) depending on the aim of the assay. The applicability of SPME technique in gas chromatography with electrons capture detection was attested in the analysis of six PCB congeners. Higher linearity, selectivity, accuracy, reproducibility and robustness was obtained in the PCB quantification analyses. The Hypothesis 1 was accepted; since the PCB congeners in the reactors were quantified by the SPME methodology. Although the PCB causes methanogenic inhibition, with IC50 of 0.03 mg.L-1 (concentration in which 50&#37; of the methanogenic metabolism is inhibited), by the Removal Assay was confirmed the anaerobic removal of 0.92 mg.L-1, 0.19 mg.L-1, 0.18 mg.L-1, 0.07 mg.L-1, 0.55 mg.L-1 and 0.47 mg.L-1 to PCB 10, 28, 52, 153, 138 and 180, respectively, for 1.5 mg.L-1 initial. By means of platform Illumina Thermotogaceae, Sedimentibacter, Anaerolinaceae and Pseudomonas, were identified in the anaerobic reactors. The Thermotogaceaeand Sedimentibacter were related to systems with high PCB removal and the Chloroflexi members (Anaerolineae phylum) were the first PCB-dechlorination microorganisms identified. Therefore, the Hypothesis 2 was accepted since the PCB leads to anaerobic inhibition and in the reactors were verified the PCB removal and changes in the microbial composition. Even with PCB, the denitrification metabolism occurs and evaluating different C/N-NO3- relations, the 6.95 was stipulated the ideal in the presence of PCB. Even though the PCB causes inhibition in the denitrification bacteria, with IC50 of 1.0 mg.L-1, by the Removal Assay in the denitrifying reactors, was confirmed the anoxic removal 1.02 mg.L-1, 0.85 mg.L-1, 1.31 mg.L-1, 1.02 mg.L-1, 0.03 mg.L-1 and 0.09 mg.L-1 to PCB 10, 28, 52, 153, 138 and 180, respectively, for 1.5 mg.L-1 initial. Aeromonadaceae, Lutispora, Sedimentibacter and Thermotogaceae were identified in the denitrifying reactors. Members of Aeromonadaceae e Lutispora were related to the denitrification metabolism and Thermotogaceae e Sedimentibacter were identified in systems with high PCB removal rate. The Hypothesis 3 was accepted since the PCB leads to anoxic inhibition and in the reactors were verified the PCB removal and changes in the microbial composition. The anaerobic reactors presented the higher PCB removal percentage (between 45&#37; and 100&#37;) when compared to the anoxic reactors (between 10&#37; and 95&#37;). Member of Sedimentibacter and Thermotogaceae were identifyied in both conditions. However, even with high relative abundance of these two groups in the reactors, it was shown distinct composition in each biomass. Thus, the Hypothesis 4 was accepted since the PCB removal was more efficient in the anaerobic condition and were verified different changes in the microbial composition in each condition.

Conventional nonpoint source pollution policies encourage the adoption of conservation practices to reduce nonpoint source pollutants by paying a portion of the cost to install best management practices. Alternative financial incentive programs, such as payment for environmental services (PES) programs, aim to improve program effectiveness by paying directly for the quantity of environment services provided, but implementing PES programs to reduce nonpoint source pollution has been challenging given the costs and technical feasibility of measuring pollutant outcomes. Bioreactors, engineered sinks that convert biologically available forms of nitrogen into an inert form (N_2), have recently been proposed to treat and remove legacy nitrogen from springs (Easton et al., 2019). Since nitrogen removal can be directly measured, there is potential to implement an outcome-based PES program. Little information exists on the costs and risks sellers face under such a program or the impact of contractual conditions. This research applies Monte Carlo simulation to a case study bioreactor in the Chesapeake Bay Watershed to estimate the financial risks and rewards to N removal service providers under different outcome-based PES contractual conditions. Results indicate that under a fifteen-year contract term and price of $25/lb/yr of nitrogen removal, outcome-based PES for denitrifying bioreactors has a high chance of generating positive financial outcomes for a commercial size case study bioreactor that removes an average of 1,279 lbs of N annually. / Master of Science / Conventional policies to reduce diffuse water pollutants encourage the adoption of conservation practices to reduce diffuse water pollutants by paying a portion of the cost to install remedial practices or technologies. Payment for environmental services (PES) programs, an alternative to conventional policies, aims to improve program effectiveness by paying directly for the quantity of environment services provided. However, implementing PES programs to reduce diffuse water pollution has been challenging given the costs and technical feasibility of measuring pollutants and outcomes of remedial efforts. Bioreactors, engineered sinks that convert the diffuse water pollutant nitrogen into a non-pollutive form, have recently been proposed to remove legacy nitrogen from springs (Easton et al., 2019). Using bioreactors, nitrogen removal can be directly measured, so there is potential for an outcome-based PES program. Little information exists on the costs and risks sellers face under such a program or the impact of contractual conditions. This research applies financial simulation to a case study bioreactor in the Chesapeake Bay Watershed to estimate the financial risks and rewards to N removal service providers under different outcome-based PES contractual conditions. Results indicate that under a fifteen-year contract term and price of $25/lb/yr of nitrogen removal, outcome-based PES for denitrifying bioreactors has a high chance of generating positive financial outcomes for a commercial size case study bioreactor that removes an average of 1,279 lbs of N annually.

No description available.

Thesis (M.Tech.: Biotechnology)-Dept. of Biotechnogy, Durban Institute of Technology, 2005 xvi, 85 leaves : ill. ; 31 cm / Atmospheric nitrogen pollution is on the increase and human activities are directly or indirectly responsible for the generation of the various nitrogen polluting compounds. This can lead to the two major problems of eutrophication and groundwater pollution. Therefore, the removal of nutrients such as nitrogen and phosphorus from wastewater is important. Nitrogen removal from wastewater is achieved by a combination of nitrification and denitrification. Thus, there is a need to identify and characterise heterotrophic denitrifying bacteria involved in denitrification in wastewater treatment systems. The aim of this study, therefore, was to characterise heterotrophic denitrifying bacteria through detailed biochemical and molecular analysis, to facilitate the understanding of their functional role in wastewater treatment systems. Drysdale (2001) isolated heterotrophic denitrifiers to obtain a culture collection of 179 isolates. This culture collection was used to screen for nitrate and nitrite reduction using the colorimetric biochemical nitrate reduction test. The isolates were thereafter Gram stained to assess their gram reaction, cellular and colonial morphology. Based on these results identical isolates were discarded and a culture collection of approximately 129 isolates remained. The genetic diversity of the culture collection was investigated by the analysis of polymerase chain reaction (PCR)-amplified 16S ribosomal DNA (rDNA) fragments on polyacrylamide gels using denaturing gradient gel electrophoresis (DGGE). Thus DNA fragments of the same length but different nucleotide sequences were effectively separated and microbial community profiles of eight predominant isolates were created. Batch experiments were conducted on these eight isolates, the results of which ultimately confirmed their characterisation and placed them into their four functional groups i.e. 3 isolates were incomplete denitrifiers, 2 isolates were true denitrifiers, 2 isolates were sequential denitrifiers and 1 isolate was an exclusive nitrite reducer.

Thesis (M.Tech.: Biotechnology)-Dept. of Biotechnogy, Durban Institute of Technology, 2005 xvi, 85 leaves : ill. ; 31 cm / Atmospheric nitrogen pollution is on the increase and human activities are directly or indirectly responsible for the generation of the various nitrogen polluting compounds. This can lead to the two major problems of eutrophication and groundwater pollution. Therefore, the removal of nutrients such as nitrogen and phosphorus from wastewater is important. Nitrogen removal from wastewater is achieved by a combination of nitrification and denitrification. Thus, there is a need to identify and characterise heterotrophic denitrifying bacteria involved in denitrification in wastewater treatment systems. The aim of this study, therefore, was to characterise heterotrophic denitrifying bacteria through detailed biochemical and molecular analysis, to facilitate the understanding of their functional role in wastewater treatment systems. Drysdale (2001) isolated heterotrophic denitrifiers to obtain a culture collection of 179 isolates. This culture collection was used to screen for nitrate and nitrite reduction using the colorimetric biochemical nitrate reduction test. The isolates were thereafter Gram stained to assess their gram reaction, cellular and colonial morphology. Based on these results identical isolates were discarded and a culture collection of approximately 129 isolates remained. The genetic diversity of the culture collection was investigated by the analysis of polymerase chain reaction (PCR)-amplified 16S ribosomal DNA (rDNA) fragments on polyacrylamide gels using denaturing gradient gel electrophoresis (DGGE). Thus DNA fragments of the same length but different nucleotide sequences were effectively separated and microbial community profiles of eight predominant isolates were created. Batch experiments were conducted on these eight isolates, the results of which ultimately confirmed their characterisation and placed them into their four functional groups i.e. 3 isolates were incomplete denitrifiers, 2 isolates were true denitrifiers, 2 isolates were sequential denitrifiers and 1 isolate was an exclusive nitrite reducer.