The purpose of this study was to search for the substrates utilized by Azotobacter vinelandii in dialysed soil media. Also, we sought to determine the relationship between these substrates and the growth and morphological variations of A. vinelandii. p-Hydroxybenzoic acid was shown to be used as the carbon and energy source by A. vinelandii in dialysed soil medium. The amount of this compound in the soil dialysed soil medium ranged from 14 to 21 micrograms per gram of soil. In a dialysed soil medium, p-hydroxybenzoic acid induced A. vinelandii to form minute bodies, similar to the filtrable forms reported by Gonzalez and Vela, although no growth of minute bodies was detected.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2006 / Includes bibliographical references.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2006. / Thesis documentation sheet inserted. Appendix reprints three papers and manuscripts co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.

Engineered nanomaterials (ENMs) are specifically designed with different functionalities to satisfy required industrial, medical or commercial purposes. The inevitable release of these materials to the environment may impact negatively bacteria that are essential for the ecosystem’s well-being. This work aimed to identify features that determine the hazardous nature of nanomaterials to bacteria. At first, the bacterial growth inhibition concentrations for silver (Ag), cupric oxide (CuO), cadmium telluride quantum dots (CdTe QDs), titanium dioxide (TiO2), nanodiamonds and multi-walled carbon nanotubes were determined on Escherichia coli K-12 MG1655 grown in 96-well plates. The nano-forms of Ag, CuO, TiO2 and the CdTe QDs were found to display more growth inhibitory effects than their bulk equivalents. The metal salts of silver and copper were still more toxic than their equivalent ENM forms; on the contrary the CdTe QDs were found to be more toxic than their metal salts equivalent. The surface coatings of the ENMs were not found to be significant contributors of bacterial growth inhibition. This screening assay could be adapted as a first tier approach; providing an early input into the hazard assessment of nanomaterials to bacteria. The upscale determination of bacterial growth inhibition tests in 250 ml Erlenmeyer flasks manifested similar results to those observed in 96-well plates. The growth inhibition tests with E. coli were also conducted in an anaerobic fermentative environment. The presence of the ENMs was not found to disrupt the functionality of the fermentation respiratory pathway of the bacterium. However, the results indicated a more severe bacterial growth inhibition response to the presence of silver, copper and the cadmium/tellurium based ENMs as compared to the aerobic growth exposures. Finally, from the adaptation of a human ingestion simulation of soil containing CuO NPs, no greater concerns of metal bioaccessibility were identified from the potential ingestion of the nano-forms of CuO versus the metal salt.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Land use change is a major driver of species loss worldwide, the extent and intensity of agricultural land use poses particular pressures for biodiversity and the ecosystem services it provides. In recent years, agroecosystems have seen the introduction of 2nd generation bioenergy crops in order to tackle anthropogenic climate change, providing a renewable alternative to fossil fuels. In this thesis I study the impact of cultivating two commercial perennial energy crops (PECs), Miscanthus x giganteus and willow short-rotation coppice, when compared to the cereal crops they replace. I investigate processes relevant to the provisioning of pollination and decomposition services and explore patterns of soil element bioaccessibility alongside analyses of the similarity and diversity of soil bacterial communities. When compared to cereals, I find a consistent increase in pollinator (hoverfly, bumblebee and butterfly/moth) wildflower visitation in the margins of willow but not Miscanthus. In Miscanthus, opposing trends arose for different pollinator taxa: butterflies/moths were more frequent flower visitors in Miscanthus margins than cereal margins, while hoverfly flower visits were most frequent in cereal margins. Furthermore, the availability of margin wildflowers was enhanced in willow but not Miscanthus and the seed set of margin phytometers was similar between Miscanthus and cereals. Cultivation of willow, in particular, may therefore yield local conservation benefits for both wildflowers and pollinators. However, there was no evidence for enhancement of pollinator activity in cereals adjacent to either PEC, indicating that the strategic cultivation of these crops is unlikely to enhance pollinator service provision in the wider agri-environment. For investigated soil elements, bioaccessibility in PECs did not differ significantly to cereal controls, and denaturing gradient gel electrophoresis (DGGE) revealed no difference in the diversity of bacterial communities. Similarly, DGGE fingerprint patterns did not indicate the development of crop specific assemblages, demonstrating that the mobility of soil elements and structure of bacterial communities were principally determined by factors other than the identity of the crop cultivated. Investigation of meso-microfaunal decomposition rates in Miscanthus using litter bags demonstrated an impact on decomposition processes, with a significant increase in winter decomposition rates in the PEC when compared to cereals.