Global ETD Search

1	Spatial and temporal variability of organic carbon metabolism in Kaoping Coastal Sea and northern South China Sea Wang, Yu-chieh 04 August 2005 (has links) This study aims to understand the influence of hydrochemical and nutrient dynamics on the metabolism of organic carbon, and to explore the relationship between the metabolism of organic carbon and air-sea fluxes of CO2 in the Kaoping coastal zone and the northern South China Sea (NSCS). Distributions of nutrients in the Kaoping Canyon increased generally with the increase of freshwater input from the Kaoping River that discharged the highest rate during the summer season. In the northern SCS, the enhanced nutrient distributions were caused by freshwater input or upwelling in coastal and shelf zones, and by vertical mixing in the central basin in winter. During the study periods, the integrated gross production (IGP) ranged from 1389 to 8918 mgC m-2d-1 in the Kaoping Canyon, and from 851 to 5032 mgC m-2d-1 in the NSCS. The integrated dark community respiration (IDCR) ranged from 919 to 5848 mgC m-2d-1 in the Kaoping Canyon, and from 435 to 10707 mgC m-2d-1 in the NSCS. The higher IGP was found in summer than in winter for both study areas, primarily due to greater inputs of freshwater from the Kaoping River and/or from the Pearl River. The deeper euphotic depth may be also responsible for higher IGP in the central basin during the summer season. Positive correlations are significant between GP (DCR) and temperature, PAR and nutrients, and negative correlations are also significant between GP (DCR) and salinity, showing the significant impacts of freshwater inputs and climatic changes on GP (DCR). However, GP was determined largely by DCR, and DCR was attributed mainly to BR (bacteria respiration) for both the Kaoping Canyon (ave., 78%) and the NSCS (ave., 65%). In addition, the ratio of IBR/IDCR ranged from 48 to 88% for the Kaoping Canyon and from 58 to 88% for the NSCS. The ratio of IGP/IDCR is an indicator of net ecosystem production, with >1 for the autotrophic system and <1 for the heterotrophic system. The ratio was greater than 1.0 for most stations during summer but was <1.0 away from the nearshore station during winter in the Kaoping Canyon. The ratio was <1.0 for all but stations near the Pearl estuary (H and H1 stations) during both summer and winter in the NSCS, indicating a year-round heterotrophic around the slope and basin of NSCS. However, this ratio was higher in winter than in summer in the NSCS, possibly resulted from higher GP in winter than in summer. The IGP/IDCR may not be the sole factor in determining the air-sea fluxes of CO2. The physical forcing such as temperature and wind velocity may be also important in determining the source or sink of CO2 in the study areas. bacterial respiration dark community respiration organic carbon gross production
2	Changing Bacterial Growth Efficiencies across a Natural Nutrient Gradient in an Oligotrophic Estuary Kiger, Amber A 27 March 2015 (has links) Recent studies have characterized coastal estuarine systems as important components of the global carbon cycle. This study investigated carbon cycling through the microbial loop of Florida Bay by use of bacterial growth efficiency calculations. Bacterial production, bacterial respiration, and other environmental parameters were measured at three sites located along a historic phosphorus-limitation gradient in Florida Bay and compared to a relatively nutrient enriched site in Biscayne Bay. A new method for measuring bacterial respiration in oligotrophic waters involving tracing respiration of 13C-glucose was developed. The results of the study indicate that 13C tracer assays may provide a better means of measuring bacterial respiration in low nutrient environments than traditional dissolved oxygen consumption-based methods due to strong correlations between incubation length and δ13C values. Results also suggest that overall bacterial growth efficiency may be lower at the most nutrient limited sites. Bacterial Respiration Bacterial Production Bacterial Growth Efficiency Stable Isotopes Florida Bay Biogeochemistry
3	Bacterial use of allochthonous organic carbon for respiration and growth in boreal freshwater systems Berggren, Martin January 2009 (has links) Aquatic systems worldwide receive large amounts of organic carbon from terrestrial sources. This ‘allochthonous’ organic carbon (AlloOC) affects critical physical and chemical properties of freshwater ecosystems, with consequences for food web structures and exchange of greenhouse gases with the atmosphere. In the boreal region, loadings of AlloOC are particularly high due to leaching from huge organic deposits in boreal forest, mire and tundra soils. A main process of AlloOC turnover in aquatic systems is its use by heterotrophic bacteria. Applying a bioassay approach, I measured the respiration and growth (production) of bacteria in northern Sweden, in streams and lakes almost totally dominated by AlloOC. The objective was to elucidate how variations in AlloOC source, age, composition and concentration impact on its use by aquatic bacteria, and how AlloOC properties, in turn, are regulated by landscape composition and by hydrology. The bacterial respiration (30-309 µg C L-1 d-1) was roughly proportional to the concentration of AlloOC (7-47 mg C L-1), but not significantly related to AlloOC source or character. Bacterial production (4-94 µg C L-1 d-1), on the other hand, was coupled to the AlloOC character, rather than concentration. A strong coupling to AlloOC character was also found for bacterial growth efficiency (0.06-0.51), i.e. production per unit of assimilated carbon. Bacterial production and growth efficiency increased with rising concentrations of low molecular weight AlloOC (carboxylic acids, free amino acids and simple carbohydrates). While the total AlloOC concentrations generally were the highest in mire-dominated catchments, low molecular weight AlloOC concentrations were much higher in forested catchments, compared to mire-dominated. These patterns were reflected in a strong landscape control of aquatic bacterial metabolism. Moreover, high flow episodes increased the export of organic carbon from forests, in relation to the export from mires, stimulating the bacterial production and growth efficiency in streams with mixed (forest and mire) catchments. The potential of AlloOC to support efficient bacterial growth decreased on time-scales of weeks to months, as the AlloOC was aged in laboratory or lake in situ conditions. To conclude, landscape, hydrology and conditions which determine AlloOC age have large influence on bacterial metabolism in boreal aquatic systems. Considering the role of bacteria in heterotrophic food chains, these factors can have spin-off effects on the structure and function of boreal aquatic ecosystems. lakes streams boreal bacterial respiration bacterial production bacterial growth efficiency allochthonous organic carbon low molecular weight compounds
4	Reguladores do metabolismo bacteriano em reservatórios tropicais / Environmental drivers of bacterial metabolism in tropical reservoirs Silva, Roberta Mafra Freitas da 10 March 2017 (has links) Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T13:00:56Z No. of bitstreams: 1 DissRMFS.pdf: 2091397 bytes, checksum: 9416d9552b0e519672969fe9b02432ff (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T13:01:05Z (GMT) No. of bitstreams: 1 DissRMFS.pdf: 2091397 bytes, checksum: 9416d9552b0e519672969fe9b02432ff (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T13:01:12Z (GMT) No. of bitstreams: 1 DissRMFS.pdf: 2091397 bytes, checksum: 9416d9552b0e519672969fe9b02432ff (MD5) / Made available in DSpace on 2017-08-22T13:01:18Z (GMT). No. of bitstreams: 1 DissRMFS.pdf: 2091397 bytes, checksum: 9416d9552b0e519672969fe9b02432ff (MD5) Previous issue date: 2017-03-10 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Reservoirs located in tropical regions are main carbon (C) sources to the atmosphere, and bacterial metabolism is a key process that regulates those emissions. However, studies on the environmental drivers of bacterial metabolism in tropical reservoirs are scarce. By measuring metabolic rates and the limnological parameters in four cascading reservoirs that form a trophic state gradient, we determined the environmental drivers of bacterial metabolism in a tropical region, and compared them with those found in the literature (mainly from temperate regions). Our multiple regression models selected variables related to the trophic state as the main drivers of bacterial production (BP) and bacterial growth efficiency (BGE). On the other hand, bacterial respiration (BR), and consequently bacterial carbon demand (BCD), were weakly and negatively correlated to dissolved organic carbon (DOC), contrasting with the literature data. BR was always high, especially in less productive reservoirs where planktonic communities were limited by phosphorus. Nutrient limitation, high temperatures and high incident light intensity increased the environmental hostility, and cells must invest more energy in maintenance mechanisms, which directs the metabolism towards BR. This was observed in the reservoirs studied, especially in the more oligotrophic environments (Nova Avanhandava and Três Irmãos) where BR was higher and ECB lower. Our results indicate that the regulatory mechanisms of bacterial metabolism may vary according to latitude. / Reservatórios de regiões tropicais são fontes de carbono (C) para a atmosfera e o metabolismo bacteriano é um processo fundamental na regulação dessas emissões. No entanto, estudos que elucidem os fatores ambientais que determinam o metabolismo bacteriano em reservatórios tropicais são ainda escassos. Neste estudo foram medidas taxas metabólicas e parâmetros limnológicos em quatro reservatórios em cascata que formam um gradiente de estado trófico, com o intuito de determinar os reguladores do metabolismo bacteriano em uma região tropical e compará-los com dados obtidos a partir da literatura disponível (principalmente de regiões temperadas). Nossos modelos de regressão múltipla selecionaram variáveis relacionadas ao estado trófico como os principais reguladores da produção bacteriana (PB) e da eficiência de crescimento bacteriano (ECB). Foi encontrada uma relação fraca e negativa entre a respiração bacteriana (RB) e o carbono orgânico dissolvido (COD), diferente dos dados da literatura. As taxas de RB foram sempre elevadas, especialmente em reservatórios menos produtivos, nos quais as comunidades planctônicas estavam limitadas por fósforo. A escassez de nutrientes, as elevadas temperaturas e a alta intensidade de luz incidente aumentam o grau de hostilidade, e as células devem investir mais energia em mecanismos de reparação, o que direciona o metabolismo para a RB. Isso foi observado nos reservatórios estudados, especialmente, nos ambientes mais oligotróficos (Nova Avanhandava e Três Irmãos) nos quais a RB foi mais elevada e a ECB mais baixa. Nossos resultados indicam que os mecanismos reguladores do metabolismo bacteriano podem variar de acordo com a latitude. / FAPESP: 14/14139-3 / FAPESP: 11/50054-4 Produção bacteriana Respiração bacteriana Eficiência de crescimento bacteriano Demanda de carbono bacteriano Gradiente de produtividade Bacterial production Bacterial respiration Bacterial growth efficiency Bacterial carbon demand Productivity gradient CIENCIAS BIOLOGICAS::ECOLOGIA
5	The Role of Bacterioplankton in Lake Erie Ecosystem Processes: Phosphorus Dynamics and Bacterial Bioenergetics Meilander, Tracey Trzebuckowski 20 November 2006 (has links) No description available. Biology, Ecology Bacterioplankton Phosphorus dynamics Bacterial bioenergetics Labile dissolved organic carbon Bacterial productivity Bacterial respiration Bacterial growth efficiency Lake Erie Hypoxia
6	Rôle de la température et des ressources nutritives dans le contrôle des activités des bactéries marines hétérotrophes : approches in situ et expérimentales / Role of temperature and resources in the control of heterotrophic marine bacteria activities : in situ and experimental approaches Céa, Benjamin 18 December 2014 (has links) Une approche in situ et expérimentale sont menées en baie de Marseille. Des mesures simultanées de PB, de RB, de la phosphatase alcaline (phos) et de la protéase (prot) sont réalisées. Des gradients de températures (12-32°C) de ces 4 activités sont effectués. Les résultats montrent que 1) les températures optimales et les Q10 varient saisonnièrement, 2) le BGE ne diminue pas nécessairement lorsque la température augmente et 3) quelles que soit les conditions in situ, l'assemblage bactérien possède un BGE à la température in situ proche de sa température optimale. Des expériences d'enrichissements en PO4 et glucose incubées à température in situ et température in situ + 3°C montrent que la nature de l'interaction entre la température et les ressources est principalement synergétique. L'hypothèse d'un scénario supposant des changements relatifs de PB, prot et phos lors d'un changement de température suggère que les taux prot/PB et phos/PB diminuent lors d'un réchauffement et augmentent lors d'un refroidissement. Enfin, ces expériences témoignent que la température et la disponibilité du PO4 sont les principaux facteurs limitant les activités hétérotrophes. L'étude du mode d'apport de la MO (pulsé ou en continu) menée sur 4 cultures saisonnières montre que selon les conditions environnementales et le mode d'apport de la MO, l'AB, la PB et la RB varient significativement. Toutefois, l'AB, la PB, la RB et le BGE ne montrent pas de différences significatives entre les réservoirs d'ajouts pulsés et d'ajouts continus de MO suggérant des communautés bactériennes peu sensibles à la nature de la perturbation nutritionnelle alors que leurs activités en sont fortement dépendantes. / In this work, in situ and experimental approaches have been carried out in Marseilles' Bay. Simultaneous measurements of bacterial production (BP), bacterial respiration (BR), alkaline phosphatase activity (phos) and protease activity (prot) have been performed. Kinetic temperatures (12-32°C) of these 4 activities have been also conducted. The results demonstrate that i) the optimum temperature and Q10 values vary seasonally, ii) BGE value does not necessarily decrease with increasing temperature and iii) whatever the in situ conditions, the bacterial assemblage has a in situ temperature BGE value close to its optimal temperature. Enrichments experiments in PO4 and glucose incubated at in situ temperature and in situ temperature + 3°C allow to observe that the synergistic nature of the interaction between temperature and resources. The assumption of a scenario assuming that BP, prot and phos changes during a temperature change suggests that prot:BP and phos:BP ratios decrease with a warming and increase with a cooling. Finally, these experiments show that temperature and PO4 availability are the main factors controlling heterotrophic activities. The study on OM availability and associated timing (pulsed or continuous) conducted during 4 seasonal cultures demonstrates that at different seasons and according to the delivery mode of OM, BA, BP and BR are varying significantly. However, the BA, BP and the BR does not show significant differences between the tanks with pulse OM addition and continuous OM addition suggesting that predominant bacterial communities are insensitive to the nature of nutritional disturbance whereas bacterial activities are highly dependent. Bactéries marines Activités hétérotrophes Production bactérienne Respiration bactérienne Bge Phosphatase alcaline Ectoaminopeptidase Température Mésocosme Solemio Marine bacteria Heterotrophic activities Bacterial production Bacterial respiration Bge Alkaline phosphatase Ectoaminopeptidase Temperature Mesocosm Solemio 550
7	Identifikation von Genen und Mikroorganismen, die an der dissimilatorischen Fe(III)-Reduktion beteiligt sind / Isolation of Genes and Microorganisms Involved in Dissimilatory Fe(III)-Reduction Özyurt, Baris 21 January 2009 (has links) No description available. 500 Naturwissenschaften allgemein Mathematics and Computer Science Metagenomik dissimilatorische Fe(III)-Reduktion Dissimilatory iron reduction DIR dissimilatory oxido-reduction of iron dissimilatory iron(III) reduction metal reduction ferricironreduction microbial iron respiration bacterial respiration microorganisms for energy production dissimilatory iron reducing bacteria dissimilatory metal reducing bacteria DMRB energy production electricity energy transduction microbial electricity electron donor electron acceptor electron transfer carbon source carbohydrate mannit mannitol biofilm mineral mineral formation microbial degradation ribosomal proteins cytochromes hypothetical proteins enzymes oxidation reduction ferric iron iron oxide Fe(II) Fe(III) soluble iron insoluble iron ferric reductase activity iron mineral formation mineralisation <i>E. coli</i> Escherichia coli environmental microorganisms life in extreme environments uncultivable bacteria soil microbial ecology anaerobic growth anaerobic incubation environmental sequences environmental DNA DNA extraction functional screening metagenomic metagenome meta-genome microbial ecology environmental genomics soil metagenome BACs sequencing bioinformatics microbial communities 16S rRNA phylogenetics 30 42.30 42.30 58.30 42.49 58.30 42.13 RA W

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