Previous studies from this and other laboratories have shown that the novel microtubule poison, JG-03-14, which binds to the colchicine binding site of tubulin, has the capacity to promote both autophagy and apoptosis in breast tumor cells, as well as interfering with endothelial cell function and potentially disrupting tumor vasculature. The current work was designed to investigate the interaction between JG-03-14 and cell culture models of colon carcinoma and melanoma, specifically HCT116 human colon carcinoma cells and B16F10 murine melanoma cells. In both cases, JG-03-14 promoted death in the bulk of the treated population. FACS analysis, DAPI and TUNEL staining indicated that only a small fraction of the cell population was undergoing apoptosis; furthermore, there was no evidence of mitotic catastrophe (micronuclei in bi-nucleated cells). Staining with acridine orange and monodansylcadaverine as well as electron microscopy demonstrated the formation of autophagic vesicles, consistent with the cells undergoing extensive autophagy. Cell cycle analysis indicated that cells had arrested in the G2/M stage, with evidence of a hyperdiploid population. Residual surviving cells appeared to be in a state of senescence; furthermore, the senescent cells failed to recover proliferative capacity, indicating that the cells were reproductively dead. Toxicity studies in cardiomyocytes with comparisons to combretastatin and taxol indicated that JG-03-14 was the less toxic of the microtubule poisons. In summary, our studies indicate that JG-03-14 induces autophagic and reproductive cell death in HCT116 colon carcinoma cells and B16F10 murine melanoma cells with limited toxicity to the normal cells that are generally susceptible to taxol and combretastatin. The possibility of alternative mode(s) of cell death (autophagy and irreversible senescence) induced by JG-03-14 makes it a potentially useful candidate as a chemotherapeutic drug that could be used to treat cancers resistant to apoptosis. The relative lack of toxicity of JG-03-14 provides additional support for its potential use in the treatment of malignancies.

Selenium (Se) is an essential micronutrient and is also used in various industrial processes. However, Se also exhibits a low toxicity threshold and therefore presents a significant risk to human kind when released into the environment. The gap between Se deficiency (< 40 µg•day−1) and acute Se poisoning (> 400 µg•day−1) for humans is rather narrow. In addition, detrimental effects to the health of humans and other biota can arise from radioactive Se isotopes. Namely, 79Se is of concern, as it is one of the fission products originating from nuclear power production. The toxicity of selenium not only depends on its concentration but also on its speciation. This of course applies to both stable and radioactive isotopes. Microorganisms play a key role in determining and altering the speciation of Se in the selenium geochemical cycle. The naturally released selenium oxyanions (selenite (SeIVO32−) and selenate (SeVIO42−)) can be microbially reduced to differently shaped biogenic elemental selenium (BioSe, Se(0)) nanomaterials - BioSe-Nanospheres and BioSe-Nanorods. Even after more than 30 years of elaborated research on selenium, the impact of the microbial biota on the shape change of these BioSe-Nanomaterials lacks a fundamental understanding. Furthermore, due to the various species of microorganisms having different metabolisms, a detailed investigation of representative organism is required to predict the fate of selenium in the environment and engineered systems. Thus, the motivation behind this Ph.D. work was to study the effect of selected microorganisms (based on their high resilience, application in wastewater treatment processes, and capability to reduce selenium oxyanions) on the properties and fate of the produced biogenic elemental selenium nanomaterials. Namely, this meant deciphering the role of selenium oxyanion reduction mechanism on the localisation (intracellular or extracellular) of the microbially produced biogenic elemental selenium nanoparticles. This understanding is important as the localisation defines the release of the selenium nanoparticles in the environment and hence its potential pathway into the food chain. Further, the role of the microorganisms (pure culture and mixed culture) on the composition and stability of the corona (organic layer) on the BioSe-Nanomaterials was studied as properties of the corona can affect the stability and hence the localization of the nanomaterials. Moreover, the effect of the microbial environment on the shape establishment and stability, as well as on the fate of the produced biogenic elemental selenium nanomaterials was also investigated. Eventually, the obtained results narrow the identified knowledge gap and improve the understanding of the fate of selenium in the environment. In the first part of this Ph.D. thesis, the bacterial strain Bacillus safensis JG-B5T was chosen to study the influence of microbes on the fate of Se in the environment due to its occurrence in uranium mining sites where selenium is also found. First, this bacterium has been analysed by genome sequencing and its genomic data were deposited at the NCBI database. With the obtained results, the bacterial strain was classified in the corresponding phylogenetic tree. Furthermore, this Ph.D. work revealed that B. safensis JG-B5T is an obligate aerobic microorganism with the ability to reduce SeO32− to elemental selenium (Se(0)) in the form of red BioSe-Nanospheres. A reduction of SeO42− has not been observed. Two-chamber reactor experiments revealed that direct contact between SeO32− and the bacterial cells was necessary to start the reduction. In addition, microscopic investigations identified changes in the bacterial cell morphologies induced by toxic stress effects of SeO32−. Only extracellular production of BioSe-Nanospheres was observed using STEM equipped with a HAADF detector. The produced BioSe-Nanospheres were characterized by Raman spectroscopy as being amorphous Se. Furthermore, a stabilizing corona containing proteins and EPS, which caps the BioSe-Nanospheres, has been identified by FT-IR spectroscopy. The detailed composition of this corona has been further studied using proteomics analysis. The combination of two-chamber reactor experiments, genome analysis and the identified corona proteins indicated that the selenite reduction process of B. safensis JG-B5T was primarily mediated through membrane-associated proteins, like succinate dehydrogenase. Thus, a detailed molecular mechanism of the microbial reduction of SeO32− to BioSe-Nanospheres by the bacterial strain B. safensis JG-B5T has been proposed within this work. Besides these investigations on the formation of BioSe-Nanospheres, ζ-potential measurements have shown a low colloidal stability of the produced BioSe-Nanospheres. Thus, B. safensis JG-B5T is an attractive candidate in selenite wastewater treatment as it provides easy ways of recovering Se while maintaining low Se discharge. These investigations motivated us to study the general role of the microbial origin and microbial environment of the discharged nanomaterials in their shape change from BioSe-Nanospheres to BioSe-Nanorods. This constitutes the second part of this Ph.D. thesis. Thus, two different known microbial BioSe-Nanospheres producers by means of selenite reduction were used, namely the bacterial strain Escherichia coli K-12 and the microbial mix culture of anaerobic granular sludge. It was shown with Raman spectroscopy and SEM imaging that the BioSe-Nanospheres produced by E. coli K-12 remain amorphous and spherical when exposed to thermophilic conditions (up to one year), whereas those obtained by anaerobic granular sludge transform to trigonal BioSe-Nanorods. ζ-potential measurements identified a decrease of the colloidal stability of the transformed BioSe-Nanorods of anaerobic granular sludge compared to the still spherical BioSe-Nanospheres of E. coli K-12. As the shape of these BioSe-Nanospheres is stabilized by their corona, detailed investigations were performed to derive key factors affecting its shape change. CheSeNMs capped with different amount of BSA were produced and incubated to evaluate the quantitative effect of the amount of proteins in the corona on the shape stability of BioSe-Nanomaterials. This experiment implied that the larger quantity of proteins present in the corona of the BioSe-Nanospheres provide better shape stability. Indeed, the BioSe-Nanospheres produced by E. coli K-12 have 5.5 times more protein than those produced by anaerobic granular sludge. To gain deeper insight into their structural properties, proteomics analysis identified the surface proteins of the BioSe-Nanomaterials. The proteomics analysis also showed that the corona of BioSe-Nanospheres produced by E. coli K-12 consists of 1009 different proteins compared to only 173 on those produced by anaerobic granular sludge. The possible difference in the interaction of the corona proteins and selenium was elucidated using density functional theory calculations. The calculations suggest the possibility of the S-Se bond formation between Se atom and sulphur of the cysteine and methionine residues of the corona proteins. Furthermore, as representative for the microbial environment the bacterial strain B. safensis JG-B5T was used to mimic the role of microorganisms living in the vicinity of the discharged nanoparticles. The bacterial strain was incubated with purified BioSe-Nanospheres produced by E. coli K-12 at mesophilic conditions. Raman spectroscopy and SEM imaging showed that in contrast to the thermophilic incubation, the BioSe-Nanospheres transformed to BioSe-Nanorods in the presence of B. safensis JG-B5T. Proteomics analysis identified that the protein corona of BioSe-Nanospheres produced by E. coli K-12 was degraded by extracellular peptidases secreted upon co-incubation with B. safensis JG-B5T bacteria, which led to their transformation to BioSe-Nanorods. All the above findings show, how microorganisms fundamentally impact the speciation, colloidal stability, and shape of selenium. These, consequently, affect their flow coefficients or partition factors in the environment and therefore their fate. This work consequently demonstrates that the shape of the BioSe-Nanomaterials depends on both, their microbial origin and their microbial surrounding. Especially, the dynamic changes induced by this microbial environment on the shape of already formed BioSe-Nanospheres after their discharge are to be further explored. This increases the complexity in determining the risk assessment of Se and probably other redox active elements, which needs to be re-evaluated and improved by including microbial criteria for better accuracy. Based on the presented investigations, further studies regarding the detailed application and expansion to other bacterial strains will continuously widen the understanding of the behaviour of Se in the environment and engineered systems.

Durch die Entwicklungen der Digitalisierung scheint 2013 die Obsoleszenz des analogen Filmmediums besiegelt. Während ein Großteil der Filmindustrie über die Flexibilität digitaler Filmaufnahmen erleichtert ist, betrauern KünsterInnen wie Tacita Dean den drohenden Verlust des analogen Mediums. Dem Anliegen, analogen Film in seinen intrinsischen Qualitäten zu erkennen, zu würdigen und zu erhalten, widmet die Künstlerin Arbeiten wie Kodak (2006) oder FILM (2011). Auch in Deans Film JG (2013) setzt sich die Künstlerin mit dem drohenden Ende des Mediums auseinander. Aufgrund seiner Rätselhaftigkeit und gesteigerten Polysemie nimmt der Film allerdings eine Sonderstellung in Deans Werk ein. Die vorliegende Arbeit sucht die Rätsel zu entziffern und zeigt auf, wie in JG dem Untergang des ‚Universums Film‘ über die Figur eines allegorischen Dramas Gestalt verliehen wird und wie über Fragmente des analogen Films ein Erinnerungsbild an die technischen und chemischen Bedingungen sowie strukturellen Eigenheiten des Mediums geschaffen wird, das allein für diejenigen in JG erkennbar wird, die mit dem Wissen um diese Bedingungen vertraut sind. In einem zweiten Schritt widmet sich die Untersuchung den Werken des britischen Science-Fiction-Schriftstellers J.G. Ballard und des US-amerikanischen Land-Art-Künstlers Robert Smithson, auf die sich Dean in JG bezieht. Über ‚close-reading‘-Analysen von Ballards The Voices of Time (1960) und Prisoner of the Coral Deep (1964) sowie Roberts Smithsons Spiral Jetty (1970) lässt sich zeigen, dass die Künstlerin Strategien zur Anwendung bringt, mit denen sie JG in unmittelbare Nähe zum Science-Fiction-Genre und zu Smithsons Land Art rückt, worüber es ihr gelingt, neben der zeitlichen auch die räumliche Dimension des Films, seine skulpturale Dimension, auf eindrückliche Weise auszustellen. / By 2013, the obsolescence of analog film seemed to be sealed as a result of progress in digitalization. While much of the film industry rejoiced in the greater flexibility provided by digital film, artists such as Tacita Dean mourned the impending loss of their analog medium. Tacita Dean had already dedicated works such as Kodak (2006) and FILM (2011) to the recognition, appreciation, and preservation of film in its intrinsic qualities. In her film JG (2013) the artist continues to deal with the impending end of the medium. JG’s enigmatic nature and heightened polysemy lends it a unique position in Dean’s œuvre. The Dissertation seeks to decipher the enigma JG and tries to show how the artist in JG confronts the impending loss of her medium. It is argued that she does this in two ways: through the figure of an allegorical drama reflecting the end of the 'universe of film’; and, secondly, through a collection of analog film fragments that, to those with the requisite knowledge, become recognizable as a commemorative picture of the technical and chemical conditions and structural characteristics of the medium. In a second step, the study is dedicated to works of British science fiction writer J.G. Ballard and American Land Art artist Robert Smithson on which Dean draws in JG. Through close-reading analyses of Ballard’s The Voices of Time (1960) and Prisoner of the Coral Deep (1964) as well as Robert Smithson’s Spiral Jetty (1970), it becomes clear that Dean employs strategies that bring JG into close proximity with the genre of Science Fiction and with Smithson’s Land Art. By these means she achieves an impressive demonstration not merely of film’s temporal but of its spatial, sculptural dimension.