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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Intestinal protein turnover : a study of the nitrogenous transactions of the small intestinal mucosa in sheep / by Alexander Lockwood Smith

Smith, Alexander Lockwood January 1979 (has links)
Typescript (photocopy) / xi, 217 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy, 1980
32

Metabolism of inorganic compounds of nitrogen and sulphur in photosynthetic bacteria /

Khanna, Sunil. January 1982 (has links) (PDF)
Thesis (Ph.D.) -- University of Adelaide, Dept. of Agricultural Biochemistry, 1983. / Typescript (Photocopy).
33

Sombreamento e aplicação de nitrogênio em plantas jovens de Jatropha curcas L

Hiraki, Simone Silva [UNESP] 26 August 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-26Bitstream added on 2014-06-13T19:39:55Z : No. of bitstreams: 1 hiraki_ss_me_ilha.pdf: 634960 bytes, checksum: 322c05fc858e94a98f166f9c7a604bc8 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O pinhão-manso (Jatropha curcas L.) é uma planta conhecida e cultivada na América desde tempos remotos, porém, somente nas últimas três décadas passou a ser estudado agronomicamente. É considerada uma espécie promissora no processo de produção de biocombustíveis devido ao seu elevado teor de óleo nas sementes. Por tratar-se de uma planta ainda em fase de domesticação, os estudos acerca de seu crescimento e fisiologia ainda são escassos, porém necessários para a expansão da cultura em todo o país, por isso, o objetivo desta pesquisa foi analisar o crescimento e o metabolismo do nitrogênio de plantas jovens de J. curcas cultivadas sob quatro condições de sombreamento (0, 30, 50 e 70 % de cobertura) e quatro concentrações de nitrato (0, 15, 30 e 45 mM). Durante 120 dias as plantas foram tratadas e avaliadas biometricamente quanto à altura, diâmetro, número de folhas, área foliar e massas fresca e seca. Fisiologicamente analisou-se a atividade das enzimas redutase do nitrato e glutamina sintetase, proteína total solúvel, análise quantitativa de nitrato e amônia. Os resultados obtidos sugerem que com relação ao crescimento inicial J. curcas é responsiva ao sombreamento, como características ecofisiológicas que se refletem em adaptações morfológicas de expansão da área foliar, alongamento do pecíolo e maior crescimento em altura buscando ambientes com maior luminosidade, sendo que ambientes com sombreamento de 30% são eficazes no controle da temperatura foliar e retenção de água no substrato permitindo o melhor desenvolvimento das plantas, entretanto, níveis acima de 50% de sombreamento são prejudiciais ao crescimento inicial da espécie por provocarem intenso estiolamento e redução no número médio de folhas. A realização da adubação nitrogenada é de suma importância... / The jatropha (Jatropha curcas L.) is a plant known in America and cultivated since ancient times, but only in the last three decades began to be studied agronomy. It is considered a promising species for the biofuels production because its high oil content in seeds. It‟s a plant still under domestication because it, studies on their growth and physiology are still scarce, but necessary to the expansion of culture throughout the country, so the objective of this research was to analyze the growth and nitrogen metabolism in young plants of J. curcas grown under four conditions of shading (0, 30, 50 and 70% coverage) and four nitrate concentrations (0, 15, 30 and 45 mM). For 120 days the plants were treated and biometrically evaluated as to height, diameter, number of leaves, leaf surface area and fresh and dry mass. Physiologically, we analyzed the enzymes activity of the nitrate reductase and glutamine synthetase, total soluble protein, quantitative analysis of nitrate and ammonia. The results suggest that with respect to the initial growth J. curcas is responsive to the shading, with physiologic characteristics that reflected in morphological adaptations of leaf area expansion, petiole elongation and greater height growth looking environments with higher brightness, and shading environments with 30% are effective in leaf temperature control and water retention in the substrate allowing for better development of plants, however, levels above 50% shading is detrimental to early growth of the species to cause intense etiolation and reduction in the number of leaves. The nitrogen fertilizer is a paramount importance in the early development of plants, the start deficiency visual symptoms appear in the first month after germination. Nitrate concentrations exceeding 30 mM are harmful because they cause a reduction... (Complete abstract click electronic access below)
34

Genetic and physiological studies on potassium and nitrogen uptake and utilization in wheat

Woodend, John J. January 1986 (has links)
Experiments were undertaken to examine the extent of variation for potassium and nitrogen uptake and utilization in wheat and also to address some issues of relevance to the improvement of these traits. These issues included the inheritance of these traits and the difficulties that could arise due to (1) the methodology that is used to measure ion fluxes and utilization, (2) ontogenetic variation in the expression of these traits, and (3) the growth stage at which nutrient utilization is evaluated. To compare varieties developed during different periods in the history of wheat breeding, the varieties were assigned to five groups on the basis of height and origin. Nutrient fluxes were measured either as average net fluxes or short-term net fluxes. Nutrient utilization was expressed as shoot fresh weight per plant, efficiency ratio or utilization efficiency. Substantial variation was observed for all traits except potassium and nitrogen efficiency ratios. Although short-term net potassium fluxes were negatively correlated with root potassium concentration, some of the differences in flux were not associated with differences in root potassium concentration. These differences must therefore be heritable. Due to the complexity of the regulation of nitrate uptake, genotypic differences in short-term net nitrate flux were not examined in relation to root nitrate concentration. Therefore, some of the variation in nitrate flux could be due to differences in root nitrate concentration or some other factor(s) which regulates nitrate uptake. Significant differences between groups were also observed. The tall varieties had the highest potassium and nitrate fluxes but were not significantly different from the triple dwarfs. The double dwarfs were the poorest performers for both nutrient uptake and utilization. In general, the tall traditional varieties were more vigorous and hence showed the highest shoot weight per plant and utilization efficiencies. These findings are examined in relation to the contention that plant breeding under high fertility conditions may have resulted in a decline in the ability of plants to acquire and utilize mineral nutrients. The inheritance of short-term net potassium flux, shoot weight per plant, potassium efficiency ratio and potassium utilization efficiency was studied in four crosses. Complex modes of inheritance were observed for all the traits. For one of the crosses significant reciprocal effects were observed for shoot weight per plant, efficiency ratio and utilization efficiency. Narrow sense heritabilities for the two traits most likely to be selected for, namely short-term net potassium flux and shoot weight per plant, indicated that selection for these traits should be carried out amongst families rather than amongst single plants. Diallel analysis for nitrate uptake and utilization indicated that both additive and dominance gene effects are important in the determination of these traits. The effect of developmental changes in potassium uptake and utilization on varietal comparisons and genetic studies was investigated by comparing the performance of six varieties at different stages of growth over a five-week period. The rankings of the varieties for short-term net potassium flux and shoot weight per plant were found to be fairly consistent. Correlations between average net fluxes for different time periods as well between short-term and average net fluxes were poor. These findings indicate that selection for differences in uptake should be based on fluxes obtained from solutions identical in concentration to the growth solution rather than on perturbation fluxes obtained by depletion of a solution much more concentrated than the growth solution. All measures of potassium utilization based on vegetative growth were poorly correlated with performance at the adult stage. Significant negative rank correlations between shoot fresh weight per plant and grain weight per plant were obtained most likely due to differences in harvest index. This finding casts some doubt on the usefulness of vegetative measures of nutrient utilization as indicators of nutrient-use efficiency for a crop in which the economic product consists of grain. / Science, Faculty of / Botany, Department of / Graduate
35

Assimilação do nitrogênio em diferentes regiões foliares de uma bromélia epífita com tanque / Nitrogen assimilation in different leaf portions of a tank epiphytic bromeliad

Cassia Ayumi Takahashi 29 August 2008 (has links)
A folha é o principal órgão de absorção e assimilação de nutrientes dos membros epífitos com tanque da família Bromeliaceae. Pouco se conhece sobre a nutrição dessas bromélias, entretanto algumas evidências (TAKAHASHI, 2007) indicaram a possibilidade de haver uma absorção preferencial do nitrogênio na porção basal e a assimilação desse nutriente na porção apical foliar. Para se compreender melhor os mecanismos de assimilação do nitrogênio utilizados pelas bromélias epífitas com tanque, foi proposto neste trabalho dois principais objetivos: 1) verificar possíveis diferenças quanto à capacidade de assimilação do nitrogênio em diferentes porções foliares de uma bromélia epífita com tanque; 2) constatar possível preferência em assimilar fonte nitrogenada orgânica ou inorgânica, quando ambas estão disponíveis no interior do tanque. A estratégia utilizada para o primeiro objetivo foi cultivar bromélias da espécie Vriesea gigantea, cultivadas em casa de vegetação e registrar em suas folhas as variações temporais das atividades enzimáticas da urease, redutase do nitrato (NR), sintetase da glutamina (GS), desidrogenase do glutamato dependente de NADH (GDH-NADH) e arginase após o fornecimento, no interior do tanque das bromélias, de uma solução nutritiva contendo NO3-/NH4+ (3:2) ou uréia (5mM de N total), como fontes de nitrogênio. Foram analisadas as atividades enzimáticas nas porções apical e basal foliar de Vriesea gigantea nos seguintes tempos: 0, 1, 3, 6, 9, 12, 24, 48, 51, 54, 57, 60 e 73 horas após a rega. Além disso, também foram quantificadas as concentrações do amônio e da uréia endógenos presentes nos tecidos foliares de ambas as porções. Os resultados mostraram que, independente do tratamento, as atividades de GS, GDH e arginase foram mais altas na porção apical em todos os tempos de coleta. Já as atividades da NR e urease, foram crescentes e mais intensas na porção basal, da mesma forma como foi visto para as concentrações endógenas de amônio durante as primeiras 24 horas. As maiores concentrações de uréia endógenas também foram registradas principalmente na porção basal foliar. Esses resultados permitem inferir que a região apical pode estar envolvida, preferencialmente, com a assimilação do nitrogênio, enquanto que a basal, com a sua absorção, redução do nitrato e hidrólise da uréia. Além disso, sugere-se também que ocorra o transporte de amônio da base para a região de sua assimilação em aminoácidos (ápice) através do xilema e apoplasto. Em relação ao segundo objetivo, a estratégia utilizada foi fornecer à bromélia Vriesea gigantea com uma solução nutritiva que continha 5mM de nitrogênio total, disponível na forma inorgânica + orgânica (NH4+/NO3- + uréia nas proporções 1:1 ou 1:3, respectivamente). Como controle foram empregados os seguintes tratamentos: ausência de nitrogênio e presença de somente fontes inorgânicas (5mM de nitrogênio total). As porções apical e basal das folhas foram coletadas 9 horas após o fornecimento das soluções nutritivas e, posteriormente, utilizadas nas análises enzimáticas referentes às atividades da urease, NR, GS, e GDH-NADH. Além disso, foram quantificados em ambas as porções os teores endógenos de amônio, uréia, amido, açúcares totais e clorofila total. Também foram determinados as densidades de tricomas e estômatos nas duas regiões foliares. Verificou-se que as maiores atividades da GS (porção apical) e GDH (porção basal) foram registradas nos dois tratamentos com uréia (1:1 e 1:3) quando comparadas com as dos dois controles. As maiores concentrações de amônio endógeno na porção basal também foram detectadas nos mesmos tratamentos com uréia (1:1 e 1:3). Já a atividade da NR apresentou os maiores valores nos tratamentos de proporção 1:1 e no controle 2 (com somente fontes inorgânicas) na porção basal foliar. De modo interessante, a GS não mostrou o mesmo desempenho nos dois tratamentos (1:1 e controle 2), sendo que, no tratamento de proporção 1:1, a atividade foi o dobro daquela registrada no controle 2. Todos esses resultados analisados em conjunto permitem inferir que a bromélia Vriesea gigantea pode ter preferência por assimilar o nitrogênio proveniente da uréia quando essa fonte se encontra disponível no interior do tanque, mesmo quando também há a presença de formas inorgânicas (nitrato e amônio). / The leaf is considered the most important vegetative organ of tank epiphytic bromeliads due to its ability to absorb and assimilate nutrients. Little is known about the nutrition of these bromeliads, but there are evidences that the basal region of the leaf may be preferentially involved with the absorption of nutrients, whereas the apical region may be involved with its assimilation (TAKAHASHI, 2007). In order to better understand the mechanisms utilized by these tank epiphytic bromeliads to optimize the nitrogen acquisition and assimilation, it was proposed in this study two main objectives: 1) verify the existence of a differential capacity to assimilate nitrogen in different leaf portions of a tank epiphytic bromeliad; 2) analyze the nitrogen assimilation preference between inorganic and organic nitrogen sources when both are available in the tank water. The experiments of the first objective were conducted using Vriesea gigantea plants, a typical specie of tank epiphytic bromeliad, cultivated in greenhouse. Nutrient solution containing NO3-/NH4+ (3:2) or urea as nitrogen source (5mM of total N) was supplied into the tank of these plants and the activities of urease, nitrate reductase (NR), glutamine synthetase (GS), NADH-dependent glutamate dehydrogenase (GDH-NADH) and arginase were quantified in apical and basal leaf portions after 0, 1, 3, 6, 9, 12, 24, 48, 51, 54, 57, 60 and 73 hours. The ammonium and urea present in the tissues were also analyzed. Independent of the nitrogen source utilized, GS, GDH and arginase activities were higher in the apical portions of leaves in all the period analyzed. On the other hand, the opposite was observed in relation to NR and urease activities. The highest activities were detected in the basal portion of leaves at all harvest times, with increasing values during the first 24 hours of experiment. Interestingly, this same pattern was also observed in relation to the endogenous ammonium and urea: the highest contents were detected in the basal portion of leaves, with a gradual increase of ammonium in the first 24 hours of analysis. These results suggest that the basal portion of leaves was preferentially involved in nitrogen uptake, nitrate reduction and urea hydrolysis, while the apical portion was the main responsible for nitrogen assimilation. Moreover, it was possible to infer that the ammonium may be transported from the base (uptake region) to the apex of the leaves (the main nitrogen assimilation region) through the xylem and apoplast. In order to analyze the nitrogen assimilation preference of Vriesea gigantea, a nutrient solution containing 5mM of nitrogen containing a mixture of inorganic and organic sources (NH4+/NO3- + urea in the proportion 1:1 or 1:3, respectively) were supplied into the tank of the bromeliads. As a control, a nutrient solution containing no nitrogen source (control 1) or 5mM of inorganic nitrogen sources (control 2) were used. The basal and apical leaf tissues were collected after 9 hours and the activities of urease, NR, GS and GDH-NADH were analyzed. Endogenous ammonium, urea, starch, total soluble carbohydrates and total chlorophyll were also quantified. Furthermore, the density of trichomes and stomata were also analyzed on the abaxial leaf surface of both regions. The highest activities of GS (apex) and GDH (base), as well as the endogenous ammonium content (base), were registered in both treatments with urea (1:1 and 1:3) in comparison with both controls. A different pattern was obtained analyzing NR: the highest activities were observed in plants that received nutrient solutions containing only inorganic nitrogen (control 2) or a mixture of inorganic and organic nitrogen in the proportion 1:1. Moreover, an interesting behavior was observed in relation to the GS activity: it was detected the double activity of this enzyme when Vriesea gigantea was in contact with a mixture of inorganic and organic nitrogen (1:1) in comparison to the plants in the presence of only inorganic nitrogen sources. All results suggest that Vriesea gigantea may have preference to assimilate organic nitrogen source (urea), when the inorganic nitrogen sources (ammonium and nitrate) are also available in the tank water.
36

Regulatory mechanism of nitrogen metabolism and stress response in the methylotrophic yeast Candida boidinii / メタノール資化性酵母Candida boidiniiにおける窒素代謝とストレス応答の制御機構

Shiraishi, Kosuke 23 March 2017 (has links)
付記する学位プログラム名: 京都大学大学院思修館 / 京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20424号 / 農博第2209号 / 新制||農||1047(附属図書館) / 学位論文||H29||N5045(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 阪井 康能, 教授 矢﨑 一史, 教授 栗原 達夫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM
37

Digestibility, Nitrogen Balance, and Blood Metabolites in Llama and Alpaca Fed Barley and Barley Alfalfa Forages.

Davies, Heather Loree 28 April 2005 (has links) (PDF)
These projects were conducted to determine the digestibility of forage diets with differing CP levels in llamas and alpacas. The Utah study was designed to compare llama and alpaca nutritional parameters to determine if nutritional recommendations for llamas can be directly extrapolated to alpacas. The first study evaluated the effects of forage quality on blood metabolites and nitrogen balance in mature, intact male llamas (n = 4, 36 ± 4.4 months, 87 ± 17 kg) at high altitude in Letanias, Bolivia (4,267 m = aprox.14,000 ft above sea level). A second experiment was conducted with eight adult gelded camelids (n = 8; 4 llamas, 24-36 months, 90 ± 10.7 kg; 4 alpacas, 24-36 months, 50 ± 4 kg) at Brigham Young University, Provo, UT (altitude 1370 m). Animals were randomly fed barley hay (B) and 80% barley/20% alfalfa hay (BA). A fresh cut grass pasture (P) was included as the third forage for Bolivian llamas. Animals were housed in metabolism crates and diets were fed for a 7 d adjustment period followed by a 5 d collection period. Feed, feed refusal, feces and urine were collected, dried and N content determined by combustion analysis. Venous blood samples were collected on d 12 at 30 min intervals over a 6 h period. Plasma was harvested and analyzed for electrolytes (Na, K, Cl, Ca, Ca++, P, Mg) and metabolites (glucose, non- esterified fatty acids (NEFAs), urea N, creatinine, albumin, total protein (TPP), osmolality (Osm)). Llamas and alpacas demonstrated differences with respect to nitrogen metabolism when consuming forage diets with differing protein concentration. Llamas showed a N maintenance requirement of 0.75 g crude N/ W0.75. Using the standard CP to digestible protein (DP) conversion factor of 0.8, llamas required 0.60 digestible N/W0.75. When consuming the same high protein barley alfalfa diet, llamas had a much greater increase in N retention than alpacas. These species differences indicate that alpacas have a higher N requirement to meet metabolic needs, and extrapolations with respect to nitrogen requirements and balance are not valid between llamas and alpacas. In the Bolivian llama trial, locally grown and harvested hycrested and Siberian wheat grass pasture (P), barley (B), and barley80%/alfalfa20% (BA) hays were fed. The Bolivian llamas were in negative N balance when fed the B and P diets. Dry matter digestibility was greater with the B and BA than P forage, and N digestibility was significantly higher with BA than either the B or P forages. Nitrogen maintenance requirement for Bolivian llamas at 4,267 m was 0.58 compared to 0.75 g crude N/W0.75 for Utah llamas, an increased digestive efficiency and a lower N maintenance requirement at higher altitude.
38

Phosphorus and nitrogen metabolism in soybeans as influenced by potassium

Henderlong, Paul Robert January 1964 (has links)
The effect of K on P and N metabolism in soybean seedlings, Glycine max, Var. Dorman, was studied in two greenhouse experiments. Yield, nutrient uptake and changes in the distribution of cellular P and N compounds served as criteria for evaluating K effects. The yield increased exponentially with time regardless of K treatments; however, increasing K levels increased the rate of yield accumulation. Phosphorus uptake was not associated with K levels. An increase in N uptake was associated with increased dry matter production rather than K levels, per se. An inverse relationship was found between per cent P and K levels. This was attributed to a dilution effect due to the increased yield with increasing K levels. An extraction-time study on the lipid-free soybean leaf residue with 1N KOH, showed that essentially all of the extractable P and N was extracted within 45 and 60 minutes, respectively. Longer extraction times caused gradual protein hydrolysis. Norit-A adsorbed P:N ratios were used to indirectly estimate the relative changes in poly-nucleotide-P (ATP and ADP) associated with K levels and ortho-P accumulation; indicating that K functions either directly or indirectly in the esterification of inorganic-P in coupled oxidative phosphorylation. From the data presented, it was concluded that under a general K stress, P metabolism exhibited a priority over N metabolism for K. Based on these data, K was found to function in the following metabolic processes: (l) peptide-protein synthesis, (2) nucleic acid base synthesis, and (3) esterification of inorganic-P. / Ph. D.
39

Nitrogen metabolism and the regulation thereof in Mycobacterium smegmatis

Kirsten, Catriona Jane 12 1900 (has links)
Thesis (PhD (Med))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The nitrogen metabolic pathway is essential for growth and survival of all living organisms including prokaryotes. Certain components of the pathway, such as the enzyme glutamine synthetase (GS), have been studied; however, little information is available regarding the pathway in the mycobacteria. Our in silico studies revealed that many of the components and mechanisms involved in the pathway appear to be conserved between closely related Actinomycetales. Therefore, we investigated three aspects of nitrogen metabolic control in Mycobacterium smegmatis; namely, transcriptional regulation of nitrogen metabolism-related genes, control of enzyme activity and the signalling cascade governing the nitrogen metabolic response. At the transcriptional level, it was found that nitrogen metabolism-related genes were regulated in response to ammonium availability. Two possible transcriptional regulators, AmtR and GlnR, which are the regulators responsible for control of nitrogen-related gene transcription in Streptomyces coelicolor and Corynebacterium glutamicum respectively, were identified in M. smegmatis. Through generation of amtR and glnR deletion mutants, we found that both potential regulators played a role in the control of nitrogen-related gene expression in M. smegmatis. GlnR acted as both an activator and repressor of gene transcription whilst AmtR appeared to activate gene expression which is different to the role its homolog plays in C. glutamicum. On a protein level we found that both GS and glutamate dehydrogenase (GDH) were responsible for ammonium assimilation in M. smegmatis and were regulated in response to ammonium availability. Two GDH isoforms (NAD+- and NADP+-specific) were identified in M. smegmatis and whereas only an NAD+-GDH was detected in M. tuberculosis. The M. tuberculosis GDH also played a largely anabolic role with regard to ammonium assimilation which is in contrast to the belief that ammonium can only be assimilated via GS in this pathogen. The signaling cascade was investigated through generation of a glnD deletion mutant in M. smegmatis. We were able to show that this pivotal protein (GlnD) was able to relay the cellular nitrogen status to the transcriptional machinery as well as to GS. The data presented in this study has advanced our understanding of the nitrogen metabolic pathway in the mycobacteria. Through elucidation of such pathways, our knowledge of mycobacterial physiology and thus infection and survival improves, which could ultimately lead to the discovery of novel mechanisms to aid in the eradication of the disease. / AFRIKAANSE OPSOMMING: Stikstof metabolisme is noodsaaklik vir die oorlewing en groei van alle organismes, prokariote ingesluit. Sekere sellulêre komponente, soos die ensiem glutamine sintetase (GS), is al tevore bestudeer, maar baie min verdere inligting is beskikbaar oor stikstof metabolisme in die mycobacteria. Ons in silico studies het gewys dat baie van die komponente en meganismes gekonserveerd gebly het tussen nou-verwante Actinomycetales. Dus het ons drie aspekte in die beheer van stikstof metabolisme ondersoek; naamlik, die transkriptionele regulering van stikstof metabolisme-verwante gene, die beheer van ensiem aktiwiteit en die sein-meganisme wat die reaksie op stikstof konsentrasie reageer. Op transkripsionele vlak het ons gevind dat stikstof metabolisme-verwante gene gereguleer word in reaksie op stikstof beskikbaarheid. AmtR en GlnR is twee moontlike transkripsie reguleerders wat verantwoordelik is vir transkripsionele beheer in onderskeidelik Streptomyces coelicolor en Corynebacterium glutamicum. Beide hierdie proteïene is geïdentifiseer in M. smegmatis. Deur die konstruksie van amtR en glnR mutante, het ons gevind dat beide potensiële reguleerders ‘n rol gespeel het in die beheer van stikstof-verwante transkripsie in M. smegmatis. GlnR het opgetree as beide ‘n aktiveerder en ‘n onderdrukker van transkripsie terwyl AmtR net ‘n aktiverende rol gespeel het. Die funksie van AmtR in M. smegmatis is dus verskillend van sy homoloog in C. glutamicum. Op proteïen-vlak het ons gevind dat beide GS en glutamaat dehidrogenase (GDH) verantwoordelik was vir die assimilasie van ammonium in M. smegmatis en albei was gereguleer in reaksie op ammonium beskikbaarheid. Twee vorme van GDH (NAD+- spesifieke- en NADP+-spesifieke GDH) was geïdentifiseer in M. smegmatis terwyl net ‘n NAD+- spesifieke GDH in M. tuberculosis gevind is. Die M. tuberculosis GDH het ook ‘n anaboliesie rol gespeel met betrekking tot ammonium assimilasie wat in teenstelling is met die huidige opvatting dat ammonium alleenlik deur GS ge-assimileer kan word. Die sein-meganisme is ondersoek deur ‘n glnD M. smegmatis mutant te konstrueer. Ons het bewys dat hierdie deurslaggewende proteïen (GlnD) die sellulêre stikstof status aan die transkripsionele masjinerie, en aan GS kon oordra. Die data wat in hierdie studie voorgelê word, het ons kennis van stikstof metabolisme in die mycobacteria gevorder. Sodanige metaboliese studies verbreed ons kennis van mycobacteriële fisiologie en dus M. tuberculosis infeksie en oorlewing en kan uiteindelik lei tot die ontdekking van unieke teiken meganismes om te help met die beheer van die siekte en nuwe middelontwikkeling.
40

Métabolisme socio-écologique des territoires d’élevage : une approche de comptabilité environnementale / Socioecological metabolism of livestock areas : an environmental accounting approach

Domingues Santos, João Pedro 15 December 2017 (has links)
Au cours du XXème siècle, l’élevage français a connu un formidable développement dont la poursuite se trouve actuellement fragilisé. L’effort de recherche sur la durabilité de l’élevage s’est focalisé sur la performance économique et environnementale, principalement au niveau de l’animal et de la ferme. Peu de travaux ont abordé les trois piliers de la durabilité à des échelles territoriales où les différentes filières animales se combinent. Une approche articulant l’élevage de ruminants et monogastriques à l’occupation du sol et à l’utilisation des ressources au niveau territorial fait actuellement défaut. Cette thèse développe une évaluation holistique de l’élevage dans les territoires métropolitains en mobilisant une batterie d’indicateurs abordant les contributions positives et négatives de l’élevage. Pour l’ensemble du territoire métropolitain, nous avons constitué trois bases de données à l’échelle départementale. La première base contient des indicateurs socioéconomiques, d’occupation du sol, et de production animale sur la période 1938-2010. La seconde base fournit pour 2010 des indicateurs de production animale et végétale. La troisième base fournit des indicateurs mesurant la contribution de l’élevage à la fourniture de services culturels, socioéconomiques et environnementaux. Avec la première base, nous avons modélisé les trajectoires d’intensification de l’élevage depuis 1938 et identifié les déterminants des dynamiques de changement de l’élevage. Avec la deuxième base, nous formalisé le métabolisme territorial de l’azote, duquel nous avons dérivés six indicateurs pour évaluer la durabilité de l’élevage. Avec la troisième base, nous avons modélisé le lien entre le niveau actuel de fourniture de services et les trajectoires d’intensification. Nos résultats révèlent une différentiation territoriale de l’intensification de l’élevage depuis 1938. Productivité et densité animale ont triplé dans les territoires de l’Ouest, et augmenté de 1.6 dans les territoires de l’Est et du Massif Central. Dans les territoires sans élevage, la surface fourragère principale a reculé de plus de la moitié, tandis que la taille des fermes a triplé et la productivité du travail a quadruplé. Le métabolisme territorial révèle un arbitrage entre autonomie en azote et productivité animale. Les impacts locaux (surplus azoté / ha) et globaux (émissions excrétion azoté / kg de produit) forment un arbitrage difficile à atténuer. L’analyse des contributions positives de l’élevage montre que les territoires ayant suivi une trajectoire herbagère fournissent des services sociaux, environnementaux et culturels; alors que les territoires hébergeant les élevages les plus productifs fournissent surtout des services socio-économiques (emplois). De par sa profondeur historique et sa couverture spatiale, cette thèse offre une analyse inédite de l’élevage et de ses performances dans les territoires. Elle apporte des connaissances pour identifier des leviers de durabilité pour l’élevage de demain. / The development of the livestock sector in the past century undergone a strong intensification. The current heterogeneity of livestock areas in France may have arisen from a spatial differentiation of intensification process. Different degrees of disconnection between livestock and land have resulted in contrasted levels of performance and impacts across areas. To date, a lot of research effort has been directed at measuring environmental impacts and economic performance of livestock systems at the farm level. Insufficient attention has been paid to the three dimensions of sustainability and to trade-offs among them. Existing livestock heterogeneities across areas also deserve more research. An approach that enables connecting livestock to land and resources, at regional level, could bring novel insights on the role of livestock in use and transformation of resources. The goal of this PhD was to develop a holistic assessment of livestock areas using multimetric indicators encompassing positive and negative contributions. We compiled three databases at the department level: i) database 1 was related to socioeconomic, land use, and production characteristics of 88 French departments, within an extensive time frame (1938-2010); ii) database 2 included data on crop, fodder and livestock production for year 2010; iii) database 3 included measures of provision of cultural, environmental and social services for 60 departments. With the first database, we created a typology of intensification trajectories based on a multivariate approach. With the second database, we assessed the nitrogen metabolism of livestock areas, based on the material flows accounting (MFA) approach, from which we derived indicators of performance and impacts to study synergies and trade-offs. With the third database, we studied the influence of past intensification on the current provision of services by the livestock sector. A multivariate approach was used to assess how different rates of change in intensification variables determined contrasted levels of services. First, we showed that the intensification of the French livestock sector was spatially differentiated and based on four trajectories, ranging from extensive to intensive livestock areas, and from crop specialized to areas where livestock had a small share of national production. Livestock productivity and stocking rates had a 3 fold increase in intensive areas, whereas extensive areas had a 1.6 fold increase. Crop specialized areas lose more than half of their original fodder area, and tripled the average farm size and more than quadrupled their labor productivity. Non-dominated livestock areas lose 30% of initial livestock population, and half of their initial fodder area. Second, the study of synergies and trade-offs revealed that gains in efficiency and economies of scale, often compromised other dimensions, e.g. through increased environmental impacts. The spatial analysis of relationship between performance and impacts revealed two types of synergies linked to the type of impact, either land or product-based. Both of which were in trade-off. Third, we showed that the provision of services was spatially structured and based on three types of service bundles, determined by different rates of change in intensification variables. Changes towards grazing systems resulted in higher provision of environmental and cultural services, whereas changes towards intensive systems resulted in higher levels of social services; but this was achieved at the cost of environmental services. This PhD thesis furthered the understanding on the temporal trajectories of livestock sector across areas in France. This knowledge could help to improve livestock sustainability. Our work provided knowledge on the drivers that shaped current intensification patterns and the provision of cultural, environmental and social services. It could be used to examine options for desirable longterm changes of the livestock sector.

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