This research evaluates two different Biological Nitrogen Removal (BNR) systems for enhanced nitrogen removal in decentralized wastewater treatment. The first study evaluated the performance of Hybrid Adsorption and Biological Treatment Systems (HABiTS) at the pilot scale with and without stage 1 effluent recirculation. HABiTS is a system developed at the bench scale in our laboratory and was designed for enhanced BNR under transient loading conditions. It consists of two stages; an ion exchange (IX) onto clinoptilolite media coupled with biological nitrification in the aerobic nitrification stage 1 and a Tire-Sulfur Adsorption Denitrification (T-SHAD) system in the anoxic denitrification stage 2. The T-SHAD process incorporates NO3- adsorption onto tire chips and Sulfur Oxidizing Denitrification (SOD) using elemental sulfur as the electron donor for NO3- reduction. Previous bench scale studies evaluated HABiTS performance under transient loadings and found significantly higher removal of nitrogen with the incorporation of adsorptive media in stage 1 and 2 compared with controls (80% compared to 73%) under transient loading conditions. In this study, we hypothesize that a HABiTS system with effluent recirculation in nitrification stage 1 may enhance nitrogen removal performance compared to that without recirculation. The following were the expected advantages of Stage 1 effluent recirculation for enhanced nitrogen removal: 1) Pre-denitrification driven by the mixture of nitrified effluent from stage 1 with high concentrations of biochemical oxygen demand (BOD) septic tank effluent. 2) Moisture maintenance in stage 1 for enhanced biofilm growth. 3) Increased mass transfer of substrates to the biofilm in stage 1. 4) Decreased ratio of BOD to Total Kjeldahl Nitrogen (TKN) in the influent of stage 1. Two side-by-side systems were run with the same media composition and fed by the same septic tank. One had a nitrification stage 1 effluent recirculation component (R-system), which operated at a 7:1 stage 1 effluent recirculation ratio for the first 49 days of the study and at 3:1 beginning on day 50 and one was operated under forward flow only conditions (FF-system). The R system removed a higher percentage of TIN (35.4%) in nitrification stage 1 compared to FF (28.8%) and had an overall TIN removal efficiency of 88.8% compared to 54.6% in FF system. As complete denitrification was observed in stage 2 throughout the study, overall removal was dependent on nitrification efficiency, and R-1 had a significantly higher NH4+ removal (87%) compared to FF-1 (70%). Alkalinity concentrations remained constant from stage 1 to stage 2, indicating that some heterotrophic denitrification was occurring along with SOD, as high amounts of sCOD leached from the tire chips in the beginning of the study, reaching sCOD concentrations of 120-160 mg L-1 then decreasing after day 10 of operation of stage 2. Sulfate concentrations from stage 2 for each side were low until the last 10 days of the study, with an average of 16.43 ± 11.36 mg L-1 SO42--S from R-2 and an average of 16.80 ± 7.98 SO42--S for FF-2 for the duration of the study, however at the end of the study when forward flow rates increased, SO42--S concentrations increased to 32 mg L-1 for R-2 and 40 mg L-1 for FF-2. Similar performance was observed in the FF system as the bench scale reactor tests. The second part of the research focused on the findings from a study of a Particulate Pyrite Autotrophic Denitrification (PPAD) process that uses pyrite as the electron donor and nitrate as the terminal electron acceptor in upflow packed bed bioreactors. The advantages of using pyrite as an electron donor for denitrification include less sulfate production and lower alkalinity requirements compared with SOD. The low alkalinity consumption of the PPAD process led to comparison of PPAD performance with and without oyster shell addition. Two columns were operated side-by-side, one packed with pyrite and sand only (P+S), while another one was packed with pyrite, sand and oyster shell (P+S+OS). Sand was used as a nonreactive biofilm carrier in the columns. My contribution to this research was to carry out Scanning Electron Microscopy-Energy-Dispersive X-Ray Spectroscopy (SEM-EDS) analysis to support the hypothesis that oyster shell contributes to nitrogen removal because it has a high capacity for biofilm attachment. SEM analysis showed that oyster shell has a rough surface, supported by its high specific surface area, and that there was more biofilm attached to oyster shell than pyrite or sand in the influent to the column. EDS results showed a decrease in atomic percentages for pyrite sulfur in the effluent of both columns (59.91% ± 0.10% to 53.94% ± 0.37% in P+S+OS column and to 57.61% ± 4.21% in P+S column). This finding indicated that sulfur was oxidized more than iron and/or the accumulation of iron species on the pyrite surface and supports the coupling of NO3- reduction with pyrite oxidation.

La zone latérale des filaments branchiaux des bivalves Codakia orbiculata et Lucina pensylvanica est le lieu d'une symbiose chimioautotrophe avec des bactéries sulfo-oxydantes hébergées dans des cellules spécialisées, appelées bactériocytes. Dans cette étude, nous nous sommes proposés de déterminer les mécanismes qui sous-tendent la plasticité cellulaire et tissulaire observée au cours des processus de décolonisation et de recolonisation bactérienne. Pour ce faire, des individus collectés dans leur milieu naturel, ont été maintenus au laboratoire dans des bacs d'eau de mer filtrée en absence de nourriture et de soufre réduit, afin de provoquer la décolonisation bactérienne des filaments branchiaux. Lorsque la branchie apparaissait purgée de ses symbiotes, les individus ont été remis dans leur habitat naturel afin de provoquer sa recolonisation. L'analyse des branchies au cours de ces processus a fait appel à des techniques variées (histologie, immunohistochimie, hybridation in situ, cytométrie en flux, dosage des protéines et spectrométrie de fluorescence X). Les résultats obtenus ont permis de montrer que l'acquisition environnementale mise en évidence chez les juvéniles des Codakia se poursuivait tout au long de la vie des adultes. Cette étude a également permis une meilleure compréhension des mécanismes tissulaires sous-jacents à la plasticité du filament branchial en mettant en évidence les processus d'apoptose et de prolifération cellulaire qui ont lieu au cours des processus de décolonisation et de recolonisation. Ces processus s'accompagnent d'une variation de la teneur en soufre élémentaire, ainsi que de la taille relative et du contenu génomique des symbiotes / The lateral zone of gills filaments of coastal bivalves Codakia orbiculata and Lucina pensylvanica is the site of chemoautotrophic symbiosis with sulfur-oxidizing bacteria, housed in specialized cells called bacteriocytes. The objective of this thesis is to determine the mechanisms underlying cel1 plasticity and tissue plasticity observed in the lateral zone of gills filaments during the processes of bacterial decolonization and recolonization. In order to do this, the individuals collected in their natural habitat were maintained at the laboratory in seawater filtered tanks, without food and reduced sulfur, to cause bacterial decolonization. When the gills seemed to be purged, the individuals were returned to their natural habitat in order to cause the bacterial recolonization of gills filaments. The analysis of the gills during these processes involves several techniques (histology, immunohistochemistry, molecular hybridization, flow cytometry, total protein assays, protein sulfur assays, X-ray fluorescence spectrometry).This study shows that symbiont acquisition can occur during the entire life of Codakia bivalves. It also allows a better understanding of gills filaments plasticity by highlighting apoptosis and cell proliferation during decolonization and recolonization processes.Theses processes are accompanied with of elemental sufur, relative size and genomic content of symbiontes.

Le retraitement des combustibles nucléaires usés par le procédé PUREX (Plutonium and Uranium Refining by Extraction) repose sur une étape préliminaire de dissolution qui se déroule en milieu acide nitrique concentré et chaud. Le pouvoir oxydant important des milieux de dissolution peut induire un phénomène de corrosion et fragiliser les équipements de structure qui y sont exposés, notamment les aciers inoxydables tel que l’acier 304L. Bien que l’acide nitrique, milieu réactionnel de dissolution, soit responsable des phénomènes de corrosion, la présence d’ions oxydants (Pu, Np…) peut changer la réaction cathodique et porter l’acier dans son domaine transpassif où il peut subir une corrosion intergranulaire. Par conséquent, la connaissance des ions oxydants, leur degré d’oxydation, leur comportement en solution et en corrosion est une nécessité pour mieux appréhender les phénomènes de corrosion et prédire les risques associés. Tout d’abord, une modélisation thermodynamique basée sur les capacités calorifiques et les enthalpies libres a permis d’estimer les coefficients d’activité stœchiométrique, activités de l’eau et coefficients de dissociation du mélange binaire HNO3-H2O à des températures supérieures à 25°C. Le recueil de ces données constitue une première étape dans la compréhension du comportement en corrosion des aciers inoxydables en milieu acide nitrique en présence d’ions oxydants. Ensuite, une étude expérimentale électrochimique couplée à des techniques analytiques ont permis d’appréhender le comportement électrochimique du plutonium en milieu HNO3, notamment l’oxydation du Pu(IV) en Pu(V) qui n’était pas identifiée dans ce milieu à ce jour. L’acquisition des données nécessaires à une modélisation électrochimique étant limitée par des facteurs physicochimiques (température et concentration en HNO3), une étude paramétrique à l’aide d’un analogue chimique non radioactif (Ce(IV)/Ce(III)) a été entreprise. La détermination d’analogie Pu-Ce (loi d’équivalence) a alors permis d’estimer les évolutions des constantes thermodynamiques et cinétiques du plutonium dans des conditions de température et de concentration en HNO3 supérieures aux limites physicochimiques. Enfin, l’étude du comportement en corrosion de l’acier 304L en milieu HNO3 en présence d’ions oxydants se compose de deux études complémentaires. Dans un premier temps une étude de la corrosion électrochimique a été réalisée en présence de Pu(VI) ou de Ce(IV). Cette étude révèle d’une part que le Pu(VI) ne contrôle pas le mécanisme de réduction contrairement au Ce(IV). Par conséquent, le Ce(IV) n’est pas un analogue du Pu(VI) en corrosion. D’autre part, elle montre que les produits de corrosion n’ont pas d’influence sur le mécanisme de corrosion et met en évidence un complexe Ce(IV)-Cr(III) qui inhibe la réduction du Ce(IV). Dans un second temps une étude de la corrosion chimique via des essais d’immersion a été entreprise. Elle a permis d’améliorer la connaissance du mécanisme de dissolution notamment en mettant en évidence la présence d’une couche de Cr(VI) en extrême surface qui pourrait avoir un lien avec le marquage des grains et les prémices de la corrosion intergranulaire. / The reprocessing of spent nuclear fuels by the PUREX process (Plutonium and Uranium Refining by Extraction) is based on a preliminary stage of dissolution which takes place in hot concentrated nitric acid. The high oxidizing power of dissolution media can induce corrosion phenomena and weaken the structural equipment exposed to it, especially stainless steels such as 304L steel. Although nitric acid is responsible of corrosion, the presence of oxidizing ions (Pu, Np ...) can change the cathodic reaction and bring the steel in its transpassive area where it may undergo intergranular corrosion. Therefore knowledge of oxidizing ions, their oxidation state, their behavior in solution and corrosion is necessary to lead to a better understanding and predict the corrosion associated risks.First, a thermodynamic model based on the heat capacity and the free enthalpies was developed to estimate the stoichiometric activity coefficients, water activities and dissociation coefficients of the binary mixture HNO3-H2O at temperatures above 25°C. The acquisition of these data is a first step in understanding the corrosion behavior of stainless steels in nitric acid in the presence of oxidizing ions.Then, an electrochemical experimental study coupled to analytical techniques enabled to understand the electrochemical behavior of the plutonium in HNO3 medium, in particular the oxidation of Pu(IV) to Pu(V) which was not identified in this medium. The acquisition of data needed for an electrochemical modeling was limited by physicochemical factors so a parametric study with a non-radioactive chemical analogue (Ce(IV)/Ce(III)) was undertaken. The determination of some analogies between plutonium and cerium has enabled to estimate the evolution of thermodynamic and kinetic constants of plutonium in condition of temperature and concentration in HNO3 higher than physicochemical limitations.Finally, the study of the corrosion behavior of 304L steel in HNO3 medium in the presence of oxidizing ions consists of two complementary studies. First a study of the electrochemical corrosion was carried out in the presence of Pu(VI) or Ce(IV). On one hand, it reveals that the Pu(VI) does not control the reduction mechanism (contrary to Ce(IV)). On the other hand, it shows that the corrosion products do not have any influence on the corrosion mechanism and highlights a Ce(IV)-Cr(III) complex which inhibits the reduction of Ce(IV). Secondly a study of chemical corrosion was undertaken through immersion tests. It has improved the knowledge of the dissolution mechanism including highlighting the presence of an extreme surface layer of Cr(VI) that could be related to a grain marking and a preliminary step of intergranular corrosion.

Mercury (Hg) is a toxic heavy metal that poses significant human and environmental health risks. Mineral-associated Hg is the largest reservoir of Hg in the environment where it can account for nearly 60% of the global Hg mass inventory. A large fraction of this pool is comprised of mercury sulfide (HgS) minerals, including metacinnabar (beta-HgS). HgS minerals have long been considered insignificant sources of Hg to aqueous or atmospheric pools in all but severely acidic environments due to their low solubility and slow abiotic dissolution kinetics. Little previous work has been conducted investigating the bacterial colonization of HgS minerals and the potential role of these mineral-associated communities in impacting the mobility of mineral-hosted Hg. To address this gap in knowledge, the studies within this dissertation employed a combination of field- and laboratory-based methods. Using culture-independent techniques, this work revealed that sulfur-oxidizing bacteria can extensively colonize metacinnabar within aerobic, near neutral pH, creek sediments, suggesting a potential role for chemolithotrophic bacteria in metacinnabar weathering. Within laboratory incubations, the dominant bacterial colonizer (Thiobacillus thioparus), induced extensive release and volatilization of metacinnabar-hosted Hg. These findings expose a new pathway for metacinnabar dissolution and point to mineral-hosted Hg as an underappreciated source of elemental Hg that may contribute to global atmospheric Hg budgets. In addition, this work elucidates the importance of thiosulfate, a major intermediate sulfur species in the environment, in stimulating metacinnabar dissolution. Therefore, the work within this dissertation shows that authigenic HgS minerals are not merely a sink for Hg within non-acidic natural environments and instead are a source of dissolved and gaseous Hg. This work provides critical information for predicting the transport of Hg in the environment and for developing appropriate management and remediation strategies for Hg-contaminated systems. / Engineering and Applied Sciences

Le stress oxydant correspond à un déséquilibre entre les défenses antioxydantes et les espèces pro-oxydantes en faveur de ces derniers. Il joue un rôle central dans de nombreuses pathologies telles que l'obésité, le diabète et les maladies cardiovasculaires. Le diabète est caractérisé par une hyperglycémie chronique, source d'un stress oxydant accru et de dommages oxydatifs tissulaires. Notamment l'hyperglycémie favorise la glycation des protéines aboutissant à la formation de produits avancés de glycation (AGE). Bien que l'action délétère des AGE soit reconnue dans le diabète, leurs rôles au niveau cardiaque et adipeux restent encore assez méconnus. L'objectif de mon travail de thèse a été de déterminer les effets du stress oxydant, induit par l'hyperglycémie et l'albumine glyquée, au niveau des tissus adipeux et cardiaque, mais aussi au niveau de lignées cellulaires adipocytaires et cardiaques. Mes résultats ont montré un impact délétère de l'hyperglycémie tant au niveau cellulaire que tissulaire. De plus, certains dysfonctionnements identifiés au niveau de cœurs ou de tissu adipeux provenant de modèle animaux diabétiques ont pu être reproduits in vitro par l'incubation de lignées cellulaires adipeuses ou cardiaques en présence d'albumine glyquée. Cette étude propose de nouveaux éléments de compréhension sur les dommages de type oxydatif dans le cadre de la pathologie diabétique et ouvre de nouvelle piste d'étude sur le rôle spécifique que pourrait exercer les AGE issus de l'albumine au niveau du tissu adipeux et cardiaque. / Oxidative stress is defined as “an imbalance between oxidants and anti-oxidants in favor of the oxidants”, leading to a disruption of redox signaling and control and/or molecular damage. It plays a central role in many diseases such as obesity, diabetes and cardiovascular diseases. Diabetes is characterized by chronic hyperglycemia, a source of increased oxidative stress and tissue oxidative damage. In particular, hyperglycemia can promote protein glycation leading to the formation of advanced glycation end products (AGEs). Although the deleterious action of AGEs in diabetes is recognized, its impact in the heart and adipose tissues remains relatively unknown. The objective of this thesis was therefore to determine the effects of hyperglycemia-induced oxidative stress together with glycated albumin on the redox balance of adipose and cardiac tissues, and also by in vitro analysis of heart and adipocyte cell lines.This study revealed enhanced oxidative stress and damage induced by hyperglycemia at both cellular and tissue levels. In addition, the oxidative damage identified in heart and adipose tissues isolated from diabetic mice could be reproduced in vitro by the incubation of adipose or cardiac cell lines in the presence of glycated albumin. The current study proposes novel insights into redox imbalance in adipose and heart tissues of diabetic/obese mice and highlights the role of AGEs (especially glycated albumin) as a putative contributor to adipocyte and cardiomyocyte dysfunction.

The oxidation of three alkyl thioethers, phenol and 2-propanol by trans-dioxo ruthenium porphyrin species, and the synthesis, characterization and reactivity of several new ruthenium porphyrin complexes are described in this thesis. The trans-dioxo species Ru(Porp)(O)₂ [Porp= the dianions of 5,10,15,20-tetramesitylporphyrin (TMP) and 5,10,15,20-(2,6-dichlorophenyl)porphyrin (OCP)] selectively oxidize diethyl-, di-n-butyl- and decylmethyl- sulfides to the corresponding sulfoxides at room temperature. The reaction is first order in [Ru] and in [thioether]. The second order rate constants for the first O-atom transfer from the Ru(TMP) system are: 7.54xl0⁻³, 1.23xl0⁻² and 1.14x10-¹ M⁻¹ s⁻¹ respectively for the three thioethers at 20.0 °C. The activation parameters for the O-atom transfer process are also determined: for Et₂S, ∆H‡= 58.3 kJ mol⁻¹ and ∆S‡= -86 J K⁻¹ mol⁻¹; for nBu₂S, AH‡= 47.4 kJ mol⁻¹and ∆S‡= -120 J K⁻¹ mol⁻¹; for DecMeS, ∆H‡= 56.5 kJ mo⁻¹ and ∆S‡= -70 J K⁻¹ mol⁻¹. A second order rate constant of 7.23xl0⁻²M⁻¹s⁻¹ is measured at 20.0 °C for the oxidation of Et₂S by Ru(OCP)(O)₂. The intermediates Ru(TMP)(OSEt₂)₂, Ru(TMP)(OSEt₂)(OSEt₂) and the final product Ru(TMP)(0SEt₂)₂,where O and S refer to O- and S- bonded sulfoxide, are observed by ¹H nmr, and the last mentioned is isolated and characterized. A mechanism is proposed, based on electrophilic attack of the O=Ru=O moiety on :SR₂ to form bis-O-bonded species which subsequently isomerizes to bis-S-bonded species via mixed species. The Ru(TMP)(O)₂/Et₂S/O₂ system at room temperature is catalytic in complex, but produces only about 5 turnovers due to poisoning of the catalyst by the reaction product. The same system at >65 °C gives higher turnovers, but now porphyrin ligand degradation is observed, perhaps via oxidation by the O=Ru=O moiety. The Ru(OCP)(0)₂/Et₂S/O₂ system at 100 °C catalytically oxidizes Et₂S to Et₂SO and Et₂SO₂ (in ~ 4:1 ratio) and the porphyrin ligand does not undergo oxidative destruction. The Ru(TMP)(O)₂ species reacts with phenol via an observed intermediate Ru(TMP)(p-O(H)C₆H₄OH)₂ to form Ru(IV)(TMP)(OC₆H₄OH)₂, a paramagnetic (S=l) complex which is isolated and characterized. The oxidation reaction is first order in both [Ru] and [phenol] with a second order rate constant 6.90x10⁻² M⁻¹ s⁻¹at 20.0 °C. A mechanism based on electrophilic attack by the O=Ru=O moiety on the aryl ring followed by proton migration is proposed. This mechanism also explains the formation of some free para-benzoquinone and 1 equivalent of water per Ru. No ortho-benzoquinone is formed in the reaction. Preliminary ⁻H nmr studies reveal that 2-propanol is oxidized to acetone by Ru(TMP)(O)₂. A paramagnetic species (S= 1) was isolated as the only porphyrin product but not characterized. A range of novel ruthenium porphyrin complexes is also prepared. The reaction of acetylene with the four-coordinate Ru(TMP) species forms [Ru(TMP)]₂(u-C₂H₂), the first reported organometallic ruthenium porphyrin dimer. The complexes, Ru(TMP)(PhCCPh) and Ru(TMP)(PhCCH), the first π-bonded alkyne species in ruthenium porphyrin chemistry, are characterized in solution. The π-bonded alkene complexes Ru(TMP)(CH₂CH₂) OPrOH).(iPrOH) and Ru(TMP)(CH₂CH₂) are isolated and characterized, while the Ru(TMP)(cyclohexene) complex is characterized in situ. The Ru(TMP)(OSEt₂)₂ complex is isolated also by the reaction of Ru(TMP)(CH₃CN)₂with Et₂SO. The Ru(TMP)(L)₂ complexes, L= OSMe₂, OSnPr₂ and OSnBu₂ are also prepared via the above method and characterized. Some new Ru(OCP) complexes, (the monocarbonyl, the bis-acetonitrile and the dioxo- species) are also isolated and characterized. / Science, Faculty of / Chemistry, Department of / Graduate

Content: Chamois leathers are basically oil tanned leathers, usually requires 10 to 15 days to process from raw skins. In chamois making, air oxidation plays a major role, free radicals initiate the oxidation process in oil, which oxidizes the double bond of the fatty acid and then the oxidized oil interacts with collagen to stabilize the skin by coating the fibers (Fig 1). In the present study an attempt has been made to reduce the time for chamois leather processing. A common oxidizing agent (Benzoyl peroxide (BPO) was utilized to enhance the oxidation of oil and reduce the time duration. It has been observed that the oxidation of oil in the presence of benzoyl peroxide has significantly reduced the duration of process from 15 to 4 days. Strength properties such as tensile, percentage elongation and organoleptic properties were found to be on par with control leather. The water absorption values of the experimental leathers improved by 1-26 %, compared with control leather. Microscopic analysis (SEM) was employed to study the fiber alignment of the chamois leathers. Take-Away: 1. Time reduction in chamois leather processing 2. Inexpensive and common oxidising agents were employed 3.Improved water absorption of chamois leather

Syntrophic acetate oxidizing bacteria convert acetate into hydrogen and carbon dioxide and through the mutualistic syntrophic partnership with methanogens the products are further converted to methane in biogas processes operating at high ammonia concentrations. There is very little known about SAOBs, only five have been characterized and had their genome analyzed. The aim of this project was to gain further knowledge about the methane producing pathway of SAOBs with a proteomic approach. Proteins were extracted from biogas sludge with a phenol-based approach and trypsin digestion and peptide recovery were performed using the Suspension Trapping method. Measurement of the peptide content was made with LC-MS/MS. The peptide profiles obtained were screened for the proteins expressed of the mesophilic SAOB Syntrophaceticus schinkii. The data supports earlier suggestions that it utilizes the Wood-Ljungdahl pathway for hydrogen production. Furthermore, the peptide profile revealed that enzymes for the glycine reductase complex and the glycine cleavage system were expressed during high ammonia concentration, indicating a potential role of these enzymes in the methane producing pathway. However, due to partial failure of the sample preparation for mass spectrometry measurements no quantification conclusions could be made. A discussion on how to further improve sample preparation methods as well as how to access the proteome to a large extent is presented.

No description available.

>Magister Scientiae - MSc / Molecular methods were used to investigate the microbial diversity and community structure of ammonia-oxidizing bacteria (AOB) associated with the roots of the Proteaceae plant family. The identification of ammonia oxidizing bacteria in this ecosystem is of particular interest since Proteaceae are adapted to acidic, low nutrient (e.g. nitrogen) soils. The ammonia monooxygenase operon was used as a molecular marker to identify ammonia-oxidizing bacteria associated with the proteoid roots of the three Proteaceae members and compared to non-plant associated soil. PCR amplification using primer sets targeting the ammonia monooxygenase gene (amoA subunits) were used to construct a clone library. Sequence diversity was determined by RFLP analysis of amoA to identify major groups of AOB of the ~-subclass of Proteobacteria in total community DNA, and DNA sequencing and phylogenetic analysis were also applied. DGGE analysis was performed to determine the community structure and distribution of ammonia-oxidizing bacteria in plant-associated and non-plant associated soils. The AOB genotypic diversity was similar in the plant-associated samples and non-plant associated soil. All AOB phylotypes belonged to Nitrosospira species and clustered with Nitrosospira cluster 3. The abundance of the amoA was quantified to be approximately 4.2 x 107 copies/g of dry soil, using a real-time PCR assay. These data suggest that the Nitrosospira species are the dominant phylotypes in that environment. This investigation provides new insights into the relationships between plants and ammonia-oxidizing bacteria in natural Fynbos ecosystems.