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Author: Rex R. Malmstrom
Publisher:
ISBN: 9780542458057
Category : Bacteria
Languages : en
Pages :
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Book Description
Bacterioplankton communities play a crucial role marine biogeochemical cycles because they mediate the flux of dissolved organic matter (DOM), which is equal to about half of primary production in the ocean. These bacterial communities are also known to be incredibly diverse and comprised of bacteria from several different phylogenetic groups. However, the relationship between microbial diversity and biogeochemical cycling remains unclear. My dissertation focused on determining the contributions of abundant bacterial phylogenetic groups to the biogeochemical flux of DOM in the ocean. One specific goal if this dissertation was the identification and quantification of bacteria that assimilate the organic sulfur compound dimethylsulfoniopropionate (DMSP). DMSP can be hydrolyzed to produce dimethylsulfide (DMS), a sulfurous gas hypothesized to moderate changes in global temperature. However, most dissolved DMSP is assimilated into bacterial biomass, a process that satisfies nearly all of the bacterial S demand in the surface waters of the ocean. Since the biogeochemical fate of DMSP can affect either climate regulation or S transfer through marine food webs, it is important to identify bacteria that metabolize DMSP. To identify and quantify bacteria assimilating DMSP, I used a combination of micro-autoradiography and fluorescence in situ hybridization (Micro-FISH) to follow 35 S-DMSP assimilation into marine bacterial communities. In addition to DMSP flux, I also investigated the ecological activity of SAR11 bacteria. Gene sequences belonging to the SAR11 clade typically dominate 16S rRNA clone libraries from the ocean, and investigations with fluorescence in situ hybridization confirm that SAR11 bacteria often make up 25--35% of bacterioplankton communities. (Abstract shortened by UMI.).
Author: Rex R. Malmstrom
Publisher:
ISBN: 9780542458057
Category : Bacteria
Languages : en
Pages :
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Book Description
Bacterioplankton communities play a crucial role marine biogeochemical cycles because they mediate the flux of dissolved organic matter (DOM), which is equal to about half of primary production in the ocean. These bacterial communities are also known to be incredibly diverse and comprised of bacteria from several different phylogenetic groups. However, the relationship between microbial diversity and biogeochemical cycling remains unclear. My dissertation focused on determining the contributions of abundant bacterial phylogenetic groups to the biogeochemical flux of DOM in the ocean. One specific goal if this dissertation was the identification and quantification of bacteria that assimilate the organic sulfur compound dimethylsulfoniopropionate (DMSP). DMSP can be hydrolyzed to produce dimethylsulfide (DMS), a sulfurous gas hypothesized to moderate changes in global temperature. However, most dissolved DMSP is assimilated into bacterial biomass, a process that satisfies nearly all of the bacterial S demand in the surface waters of the ocean. Since the biogeochemical fate of DMSP can affect either climate regulation or S transfer through marine food webs, it is important to identify bacteria that metabolize DMSP. To identify and quantify bacteria assimilating DMSP, I used a combination of micro-autoradiography and fluorescence in situ hybridization (Micro-FISH) to follow 35 S-DMSP assimilation into marine bacterial communities. In addition to DMSP flux, I also investigated the ecological activity of SAR11 bacteria. Gene sequences belonging to the SAR11 clade typically dominate 16S rRNA clone libraries from the ocean, and investigations with fluorescence in situ hybridization confirm that SAR11 bacteria often make up 25--35% of bacterioplankton communities. (Abstract shortened by UMI.).
Author: Hila Elifantz
Publisher:
ISBN: 9789570516012
Category :
Languages : en
Pages : 127
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Book Description
The current study added to the growing information regarding the composition of bacterial community in aquatic environments and the role of specific bacterial groups in DOM assimilation. In particular, this study was the first to unfold the relation between structure and function of the bacterial community in the Arctic Ocean, the only cold environment studied in that aspect to date. The molecular study of GH5 revealed the potential of the community for polysaccharides degradation, however, more need to be done to broaden our understanding of the mineralization of these compounds in the marine environment.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The flux of dissolved organic matter (DOM) through aquatic bacterial communities is a major process in carbon cycling in the oceans and other aquatic systems. Our work addressed the general hypothesis that the phylogenetic make-up of bacterial communities and the abundances of key types of bacteria are important factors influencing the processing of DOM in aquatic ecosystems. Since most bacteria are not easily cultivated, the phylogenetic diversity of these microbes has to be assessed using culture-independent approaches. Even if the relevant bacteria were cultivated, their activity in the lab would likely differ from that under environmental conditions. This project found variation in DOM uptake by the major bacterial groups found in coastal waters. In brief, the data suggest substantial differences among groups in the use of high and molecular weight DOM components. It also made key discoveries about the role of light in affecting this uptake especially by cyanobacteria. In the North Atlantic Ocean, for example, over half of the light-stimulated uptake was by the coccoid cyanobacterium, Prochlorococcus, with the remaining uptake due to Synechococcus and other photoheterotrophic bacteria. The project also examined in detail the degradation of one organic matter component, chitin, which is often said to be the second most abundant compound in the biosphere. The findings of this project contribute to our understanding of DOM fluxes and microbial dynamics supported by those fluxes. It is possible that these findings will lead to improvements in models of the carbon cycle that have compartments for dissolved organic carbon (DOC), the largest pool of organic carbon in the oceans.
Author: Johanna Sjöstedt
Publisher: Frontiers Media SA
ISBN: 2889711021
Category : Science
Languages : en
Pages : 255
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Book Description
Author: Rima Franklin
Publisher: Springer Science & Business Media
ISBN: 1402062168
Category : Science
Languages : en
Pages : 339
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Book Description
This volume highlights recent advances that have contributed to our understanding of spatial patterns and scale issues in microbial ecology. The book brings together research conducted at a range of spatial scales (from μm to km) and in a variety of different types of environments. These topics are addressed in a quantitative manner, and a primer on statistical methods is included. In soil ecosystems, both bacteria and fungi are discussed.
Author: Tiffany R. A. Straza
Publisher:
ISBN: 9781109671926
Category : Bacteria
Languages : en
Pages :
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Book Description
Microbial communities dominate the fluxes of organic material in the ocean, in part due to their high abundance. To determine the amount of carbon processed by bacteria, bulk properties, such as production, abundance, biomass, and respiration, are measured for the total community. Phylogenetic analyses of bacteria are used to describe the structure within microbial communities. However, neither bulk activity measurements nor phylogenetic identification alone can determine which bacterial groups respond to certain environmental conditions or which bacterial groups use certain organic compounds. The goal of this dissertation was to assess the responses of different bacterial taxa to environmental conditions and available substrates. A basic characteristic of microbes is cell size. The size of microbial cells affects ecological interactions with other organisms and may be related to rates of biomass production. Using a protein stain, I analyzed the biovolume of microbial communities in Arctic, Antarctic, and temperate waters. Microbes in higher latitudes were on average 30% larger than cells from temperate waters. The abundance of bacterial taxa varied among geographic regions, and the size of some bacterial groups also differed among regions. Gammaproteobacteria and members of the Sphingobacteria-Flavobacteria (SF) group were larger in high latitude waters. In each environment, SF cells were larger than other bacteria by about 15%, while Gammaproteobacteria were intermediate in size and Alphaproteobacteria did not differ in size from the average bacterial cell. In addition to varying in size, bacterial taxa differ in the use of organic material. I used microautoradiography and fluorescent in situ hybridization to identify bacteria incorporating organic compounds. In the Delaware estuary and mid- Atlantic bight, about 30% of all cells incorporated leucine and other amino acids, while only 10% incorporated protein. Using light and dark treatments, I found that light affected single-cell activity in about 20% of cases, but there was no net effect of light on bulk bacterial production. Light did not affect Gamma - and Alphaproteobacteria differently. However, 25% more bacteria in the SAR11 clade used leucine in the light than the total community. Other environmental conditions besides light also correlated with the abundance and activity of bacterial groups. Gammaproteobacterial abundance correlated with bacterial production and concentrations of dissolved organic carbon and nitrogen, and a higher fraction of Gammaproteobacteria used leucine in the summer than in the fall. There is also geographic variation in abundance and activity of specific bacterial taxa. I examined the abundance and single-cell activity of dominant bacterial clades in waters off the west Antarctic peninsula. More bacteria used leucine (40%) than used a mixture of amino acids or protein (12-22%). Gammaproteobacteria were a large fraction (20%) of the community in this region, and using a new probe I assessed the ecological role of the Ant4D3 gammaproteobacterial clade. The Ant4D3 clade constituted 10% of the total community, and while the active fraction of this clade did not differ among various compounds, Ant4D3 dominated the incorporation of amino acids. The use of organic material varied among the Polaribacter, SAR11, and Ant4D3 clades. Polaribacter contributed the most to protein uptake. Though dominated by different bacterial taxa, the activity of this Antarctic microbial community was comparable to that of temperate communities. The research presented in Chapter 4 is the first description of the single-cell activity of bacterial groups in coastal Antarctic waters. The research described in this dissertation details the abundance of specific bacterial groups along with bacterial cell size (Chapter 2), light effects on bacterial activity (Chapter 3), and bacterial activity in polar waters (Chapter 4). Generally the approach taken was to divide the "black box" of all microbes into broad phylogenetic groups, which display characteristic differences yet are abundant as cohesive units in the microbial community. Assessing microbial communities at this scale, I found variation of broad bacterial taxa in size, activity, and response to environmental factors. The combination of single-cell methods with genomic approaches will enable us to move toward quantifying bacterial contribution to global processes and predicting the response of bacterial groups to environmental change.
Author: Julie Dinasquet
Publisher: Frontiers Media SA
ISBN: 2889455130
Category :
Languages : en
Pages : 315
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Book Description
Marine and freshwater polar environments are characterized by intense physical forces and strong seasonal variations. The persistent cold and sometimes inhospitable conditions create unique ecosystems and habitats for microbial life. Polar microbial communities are diverse productive assemblages, which drive biogeochemical cycles and support higher food-webs across the Arctic and over much of the Antarctic. Recent studies on the biogeography of microbial species have revealed phylogenetically diverse polar ecotypes, suggesting adaptation to seasonal darkness, sea-ice coverage and high summer irradiance. Because of the diversity of habitats related to atmospheric and oceanic circulation, and the formation and melting of ice, high latitude oceans and lakes are ideal environments to investigate composition and functionality of microbial communities. In addition, polar regions are responding more dramatically to climate change compared to temperate environments and there is an urgent need to identify sensitive indicators of ecosystem history, that may be sentinels for change or adaptation. For instance, Antarctic lakes provide useful model systems to study microbial evolution and climate history. Hence, it becomes essential and timely to better understand factors controlling the microbes, and how, in turn, they may affect the functioning of these fragile ecosystems. Polar microbiology is an expanding field of research with exciting possibilities to provide new insights into microbial ecology and evolution. With this Research Topic we seek to bring together polar microbiologists studying different aquatic systems and components of the microbial food web, to stimulate discussion and reflect on these sensitive environments in a changing world perspective.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 884
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Book Description
Author: Alejandro A. Murillo
Publisher: Frontiers Media SA
ISBN: 2889632768
Category :
Languages : en
Pages : 179
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Book Description
Author: Stuart Findlay
Publisher: Academic Press
ISBN: 0122563719
Category : Nature
Languages : en
Pages : 534
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Book Description
Overviews of the source, supply and variability of DOM, surveys of the processes that mediate inputs to microbial food webs, and syntheses consolidating research findings provide a comprehensive review of what is known of DOM in freshwater. This book will be important to anyone interested in understanding the fundamental factors associated with DOM that control aquatic ecosystems."--BOOK JACKET.
