Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 124-142).

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 69-72). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 156-175).

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 51-57). Also available on the World Wide Web.

Thesis (doctoral)--Chalmers Tekniska högskola, 1972. / "Akademisk avhandling för filosofie doktorsexamen i kemi ... fredagen den 2 juni 1972 ... Chalmers tekniska högskola."

No description available.

Recent research in microbial ecology has focused on how aquatic bacterial communities are assembled. Only a few of these studies follow a “Gleasonian” approach where the roles of single bacterial populations are in focus. In this thesis, novel molecular tools were used to describe the distribution and evolutionary relationships of microbes in productive aquatic environments. Many new phylogenetic groups of bacteria were identified, likely representing bacterial populations restricted to productive freshwaters. I also addressed the dynamics and functional role of individual bacterial populations in eutrophic lakes and brackish environments with a focus on either biogeochemically significant or potentially pathogenic representatives. Flavobacteria blooms were observed, on occasions characterized by high heterotrophic production. In addition to high temporal dynamics microbial community composition and function differed on the spatial scale, as exemplified by free-living and Cyanobacteria-associated habitats. At the community scale, microbial processes, such as biomass production and substrate uptake could be predicted from the presence and absence of individual bacterial populations. I also studied the niches of potentially pathogenic Vibrio populations in various coastal waters. Using a novel culture-independent method, a V. cholerae population was detected along the entire Swedish coastline. Results from an environmental survey and a laboratory mesocosm experiment reveal that phytoplankton-derived dissolved organic matter enhance the growth of V. cholerae and other Vibrio spp. and hence create a largely overlooked niche for these heterotrophic bacteria. This thesis and future work on the role of individual bacterial populations will facilitate predictions of biogeochemical cycles and the distribution of bacteria in the context of global climate change and local eutrophication.

Thesis (MSc)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The changes in carbon allocation to sucrose, hexoses, fibre, starch and respiration were investigated in developing internodes of sugarcane. Radiolabelling studies were conducted on internode 3, 6 and 9 tissue, representing three stages of increasing maturity. It was apparent that a high rate of cycling between triose-phosphate and hexose-phosphate occurred. A maximum of 50% of carbon entering triose-phosphates was returned to hexose-phosphate in internode 3 tissue, and this flux decreased with tissue maturity to 30%. Carbon partitioning into sucrose increased from 34% of total 14C uptake in internode 3, to 61% in internodes 6 and 9. In immature tissue, the protein and fibre components were the dominant competing sinks with sucrose for incoming carbon, to which 14 and 16% of carbon were allocated respectively. Increased carbon allocation to sucrose with tissue maturity, coincided with a decrease in partitioning to fibre. This indicated that previous studies had underestimated total carbon allocation to respiration, since the protein component was not considered. In contrast with earlier work, the respiratory pathway was the strongest competitor with sucrose for incoming carbon, even in mature tissue. Between internodes 3 and 6, carbon allocation to total respiration did not change significantly, but decreased 50% in mature tissue. Starch was a weak competitor with sucrose, for incoming carbon, to which a maximum of 2% of 14Cwas allocated in immature tissue. In cane harvested in early spring, radiolabelled maltose was recovered in internode 3 tissue of ripening cane, indicating that concomitant starch synthesis and degradation occurred. The. redistribution of C-1 and C-6 in starch glucose was analysed following feeding of tissue with [1_14C]_and [6_14C]_glucose. Randomization of label in starch indicated that the pathway for carbon movement into sugarcane plastids for starch synthesis is primarily through the triose-phosphate translocator. Finally, this study indicated that radiolabelling of tissue discs is a suitable experimental system to determine carbon flux in sugarcane. During the 3 h labelling period the rate of 14C02 release became linear, indicating that the system approached isotopic steady state between the external and internal glucose pool; and the respiratory processes involved in CO2 release. / AFRIKAANSE OPSOMMING: Die veranderinge in koolstoftoedeling na sukrose, heksoses, vesel, stysel en respirasie is in ontwikkelende internodes van suikerriet ondersoek. Die koolhidraatmetabolisme in internodes 3, 6 en 9, wat drie stadiums van toenemende rypheid verteenwoordig, is met behulp van 14Cmerkingstudies ondersoek. Dit is duidelik dat daar 'n hoë mate van koolstofsirkulering tussen die heksose- en triose-fosfaat poele voorkom. In internode 3 word tot 50% van die koolstofwat in triose-fosfate geïnkorporeer is, weer na heksosefosfaat omgeskakel. Selfs in volwasse weefsel vind daar nog soveel as 30% koolstofsirkukering plaas tussen die twee poele plaas. Koolstoftoedeling vanaf glukose na sukrose het van 34% in internode 3, tot 61% in internodes 6 en 9 toegeneem. Proteïn en selwandkomponente was die belangrikste swelgpunte vir koolstof in onvolwasse weefsel gewees. Namate die weefsel meer volwasse word, word sukrose 'n belangriker swelgpunt. Die koolstoftoedeling aan sukrose is veral ten koste van toedeling aan die selwandkomponente. Die bevinding dat die proteïenpoel 'n sterk swelgpunt is dui aan dat vorige studies die belang van respiratoriese koolstofvloei onderskat het. In teenstelling met vorige aansprake is dit duidelik dat selfs in volwasse weefsel respirasie die grootste swelpunt vir die inkomende organiese koolstof in die internode vorm. Koolstoftoedeling aan respirasie het nie noemenswaardig tussen internodes 3 en 6 verskil nie, maar het met 50% in volwasse weefsel afgeneem. Stysel is deurgaans 'n swak swelgpunt vir koolstof met die hoogste toedeling aan die poel (2%) in die jong weefsel (internode 3) . Na toediening van [U- 14C]-glukose is radioaktief gemerkte maltose gevind in suikerriet wat vroeg in die lente geoes is. Dit dui aan dat gelyktydige afbraak en sintese van stysel plaasgevind het. Die herverdeling van C-l en C-6 in glukose afkomstig van stysel is na toediening van [1_14C]_ en [6-14C]-glukose ontleed. Die ewekansige verspreiding van radioaktiwiteit tussen koolstof 1 en 6 van die glukose in stysel dui aan dat dit hoofsaaklik die triose-fosfaat translokeerder is wat in die plastied verantwoordelik is. Hierdie studie het ook aangetoon dat radioaktiewe merking van weefselsnitte 'n geskikte eksperimentele sisteem is om koolstoftoedeling in suikerriet te ondersoek. Die patroon van 14C02 vrystelling dui daarop dat die weefsel na 'n 3 h inkuberingsperiode isotopiese ewewig tussen die eksterne en interne glukose poele en die respiratoriese prosesse begin bereik het.

Carbon dioxide release from fossil-fuel burning is significant enough that we may soon experience perceptible changes in climate with important human consequences. Man's activities involving deforestation and agriculture have undoubtedly also affected atmospheric CO₂, although quantitative, and even qualitative, net effects of these processes are incompletely understood relative to fossil-fuel production. An accurate reconstruction of past ¹³C/¹²C ratios of atmospheric CO₂ may provide key constraints on the historical activity of the biosphere as CO₂ source or sink. Tree rings appear to be a repository of this information but there is much noise in the collection of previous reconstructions, presumably associated with site selection, radial variability, choice of representative wood chemical constituent, and subtle effects of climate on fractionation. This study attempts to avoid these pitfalls and develop a 50-yr δ¹³C(ATM) record from juniper trees (genus Juniperus), in fact, by taking advantage of the influence of climate on fractionation. Trees were harvested from suitable sites in close proximity to weather stations with monthly records of temperature and precipitation. Ring material was then separated from each of the sections in 5-yr intervals from 1930 to 1979 around their full circumference, and cellulose was extracted from the wood. After measuring δ¹³C of the cellulose by standard mass-spectrometric techniques, a variety of δ¹³C vs. climate functions were examined for each interval. The most useful relationships for at most 7 of the 10 sites were δ¹³C with December temperature or precipitation, because the coefficients were nearly constant from one interval to the next (averaging -0.27%₀ °C⁻¹ for temperature and -0.04%₀ mm⁻¹ for precipitation) and the intercepts differed. Local pollution effects are believed responsible for the three anomalous sites. The separation of these regression lines of different intervals is interpreted as the response of the trees to the changing δ¹³C of atmospheric CO₂ so that δ¹³C(ATM) curves are constructed from this spacing. The shape of the best-fit reconstruction suggests the biosphere has acted as CO₂ source to about 1965 and may now be a net sink. Although these conclusions are limited by certain assumptions and statistical restrictions, evidence from the recent scientific literature tends to support the increasing role of the biosphere as an important carbon sink.

No description available.