Matching Items (65)
Filtering by
- All Subjects: Microbiology
- All Subjects: Creative Project
- Creators: School of Life Sciences
- Member of: Theses and Dissertations
Description
With the aid of metabolic pathways engineering, microbes are finding increased use as biocatalysts to convert renewable biomass resources into fine chemicals, pharmaceuticals and other valuable compounds. These alternative, bio-based production routes offer distinct advantages over traditional synthesis methods, including lower energy requirements, rendering them as more "green" and "eco-friendly". Escherichia coli has recently been engineered to produce the aromatic chemicals (S)-styrene oxide and phenol directly from renewable glucose. Several factors, however, limit the viability of this approach, including low titers caused by product inhibition and/or low metabolic flux through the engineered pathways. This thesis focuses on addressing these concerns using magnetic mesoporous carbon powders as adsorbents for continuous, in-situ product removal as a means to alleviate such limitations. Using process engineering as a means to troubleshoot metabolic pathways by continuously removing products, increased yields are achieved from both pathways. By performing case studies in product toxicity and reaction equilibrium it was concluded that each step of a metabolic pathway can be optimized by the strategic use of in-situ adsorption as a process engineering tool.
ContributorsVasudevan, Anirudh (Author) / Nielsen, David R (Thesis advisor) / Torres, César I (Committee member) / Wang, Xuan (Committee member) / Arizona State University (Publisher)
Created2014
Description
The Multiple Antibiotic Resistance Regulator Family (MarR) are transcriptional regulators, many of which forms a dimer. Transcriptional regulation provides bacteria a stabilized responding system to ensure the bacteria is able to efficiently adapt to different environmental conditions. The main function of the MarR family is to create multiple antibiotic resistance from a mutated protein; this process occurs when the MarR regulates an operon. We hypothesized that different transcriptional regulator genes have interactions with each other. It is known that Salmonella pagC transcription is activated by three regulators, i.e., SlyA, MprA, and PhoP. Bacterial Adenylate Cyclase-based Two-Hybrid (BACTH) system was used to research the protein-protein interactions in SlyA, MprA, and PhoP as heterodimers and homodimers in vivo. Two fragments, T25 and T18, that lack endogenous adenylate cyclase activity, were used for construction of chimeric proteins and reconstruction of adenylate cyclase activity was tested. The significant adenylate cyclase activities has proved that SlyA is able to form homodimers. However, weak adenylate cyclase activities in this study has proved that MprA and PhoP are not likely to form homodimers, and no protein-protein interactions were detected in between SlyA, MprA and PhoP, which no heterodimers have formed in between three transcriptional regulators.
ContributorsTao, Zenan (Author) / Shi, Yixin (Thesis advisor) / Wang, Xuan (Committee member) / Bean, Heather (Committee member) / Arizona State University (Publisher)
Created2018
Description
Lignocellulosic biomass represents a renewable domestic feedstock that can support large-scale biochemical production processes for fuels and specialty chemicals. However, cost-effective conversion of lignocellulosic sugars into valuable chemicals by microorganisms still remains a challenge. Biomass recalcitrance to saccharification, microbial substrate utilization, bioproduct titer toxicity, and toxic chemicals associated with chemical pretreatments are at the center of the bottlenecks limiting further commercialization of lignocellulose conversion. Genetic and metabolic engineering has allowed researchers to manipulate microorganisms to overcome some of these challenges, but new innovative approaches are needed to make the process more commercially viable. Transport proteins represent an underexplored target in genetic engineering that can potentially help to control the input of lignocellulosic substrate and output of products/toxins in microbial biocatalysts. In this work, I characterize and explore the use of transport systems to increase substrate utilization, conserve energy, increase tolerance, and enhance biocatalyst performance.
ContributorsKurgan, Gavin (Author) / Wang, Xuan (Thesis advisor) / Nielsen, David (Committee member) / Misra, Rajeev (Committee member) / Nannenga, Brent (Committee member) / Arizona State University (Publisher)
Created2018
Description
Synechocystis sp. PCC 6803 is a readily transformable cyanobacteria used to study cyanobacterial genetics, as well as production of biofuels, polyesters, and other industrial chemicals. Free fatty acids are precursors to biofuels which are used by Synechocystis cells as a means of energy storage. By genetically modifying the cyanobacteria to expel these chemicals, costs associated with retrieving the products will be reduced; concurrently, the bacteria will be able to produce the products at a higher concentration. This is achieved by adding genes encoding components of the Escherichia coli AcrAB-TolC efflux system, part of the resistance-nodulation-division (RND) transporter family, to Synechocystis sp. PCC 6803. AcrAB-TolC is a relatively promiscuous multidrug efflux pump that is noted for expelling a wide range of substrates including dyes, organic solvents, antibiotics, and free fatty acids. Adding components of the AcrAB-TolC multidrug efflux pump to a previously created high free fatty acid producing strain, SD277, allowed cells to move more free fatty acids to the extracellular environment than did the parent strain. Some of these modifications also improved tolerance to antibiotics and a dye, rhodamine 6G. To confirm the function of this exogenous efflux pump, the genes encoding components of the AcrAB-TolC efflux pump were also added to Synechocystis sp. PCC 6803 and shown to grow on a greater concentration of various antibiotics and rhodamine 6G. Various endogenous efflux systems have been elucidated, but their usefulness in expelling products currently generated in Synechocystis is limited. Most of the elucidated pumps in the cyanobacteria are part of the ATP-binding cassette superfamily. The knowledge of the resistance-nodulation-division (RND) family transporters is limited. Two genes in Synechocystis sp. PCC 6803, slr2131 and sll0180 encoding homologs to the genes that encode acrB and acrA, respectively, were removed and the modifications resulted in changes in resistance to various antibiotics and a dye and also had an impact on free fatty acid secretion. Both of these deletions were complemented independently with the homologous E. coli gene and the resulting cyanobacteria strains had some of the inherent resistance restored to chloramphenicol and free fatty acid secretion was modified when compared to the wild-type and a high free fatty acid producing strain.
ContributorsBellefleur, Matthew Paul Allen (Author) / Curtiss, III, Roy (Thesis advisor) / Nielsen, David R (Committee member) / Wang, Xuan (Committee member) / Rittmann, Bruce E. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Space microbiology, or the study of microorganisms in space, has significant applications for both human spaceflight and Earth-based medicine. This thesis traces the evolution of the field of space microbiology since its creation in 1935. Beginning with simple studies to determine if terrestrial life could survive spaceflight, the field of space microbiology has grown to encompass a substantial body of work that is now recognized as an essential component of NASA' research endeavors. Part one provides an overview of the early period of space microbiology, from high-altitude balloon and rocket studies to work conducted during the Apollo program. Part two summarizes the current state of the field, with a specific focus on the revolutionary contributions made by the Nickerson lab at the Biodesign Institute at ASU using the NASA-designed Rotating Wall Vessel (RWV) Bioreactor. Finally, part three highlights the research I've conducted in the Nickerson lab, as well as continuing studies within the field of space microbiology.
ContributorsMcCarthy, Breanne E. (Author) / Lynch, John (Thesis director) / Foy, Joseph (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Students Organize for Syria (SOS) is the student led initiative for Syria. With 18 registered chapters across the United States, this student organization is targeting a multidimensional cause by different means. Though it is now a national movement, it started off with one group at Arizona State University, with one student. Zana Alattar, founder and student director of SOS, tells the story of how she took an ASU organization, Save Our Syrian Freedom (SOS Freedom), to the national level as SOS. As a pre-medical student, she also combines her work in human rights with her future in healthcare. After all, health and human rights have long maintained a synergistic relationship.
ContributorsAlattar, Zana (Author) / Graff, Sarah (Thesis director) / McClurg, Sharolyn (Committee member) / School of Molecular Sciences (Contributor) / School of Social Transformation (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Many bacteria actively import environmental DNA and incorporate it into their genomes. This behavior, referred to as transformation, has been described in many species from diverse taxonomic backgrounds. Transformation is expected to carry some selective advantages similar to those postulated for meiotic sex in eukaryotes. However, the accumulation of loss-of-function alleles at transformation loci and an increased mutational load from recombining with DNA from dead cells create additional costs to transformation. These costs have been shown to outweigh many of the benefits of recombination under a variety of likely parameters. We investigate an additional proposed benefit of sexual recombination, the Red Queen hypothesis, as it relates to bacterial transformation. Here we describe a computational model showing that host-pathogen coevolution may provide a large selective benefit to transformation and allow transforming cells to invade an environment dominated by otherwise equal non-transformers. Furthermore, we observe that host-pathogen dynamics cause the selection pressure on transformation to vary extensively in time, explaining the tight regulation and wide variety of rates observed in naturally competent bacteria. Host-pathogen dynamics may explain the evolution and maintenance of natural competence despite its associated costs.
ContributorsPalmer, Nathan David (Author) / Cartwright, Reed (Thesis director) / Wang, Xuan (Committee member) / Sievert, Chris (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Clean water for drinking, food preparation, and bathing is essential for astronaut health and safety during long duration habitation of the International Space Station (ISS), including future missions to Mars. Despite stringent water treatment and recycling efforts on the ISS, it is impossible to completely prevent microbial contamination of onboard water supplies. In this work, we used a spaceflight analogue culture system to better understand how the microgravity environment can influence the pathogenesis-related characteristics of Burkholderia cepacia complex (Bcc), an opportunistic pathogen previously recovered from the ISS water system. The results of the present study suggest that there may be important differences in how this pathogen can respond and adapt to spaceflight and other low fluid shear environments encountered during their natural life cycles. Future studies are aimed at understanding the underlying mechanisms responsible for these phenotypes.
ContributorsKang, Bianca Younseon (Author) / Nickerson, Cheryl (Thesis director) / Barrila, Jennifer (Committee member) / Ott, Mark (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Vaccinia virus (VV) is a prototype virus of the Orthopox viruses. The large dsDNA virus composed of 200kbp genome contains approximately 200 genes and replicates entirely in the cytosol. Since its use as a live vaccine against smallpox that leads to the successful eradication of smallpox, Vaccinia has been intensely studied as a vaccine vector since the large genome allows for the insertion of multiple genes. It is also studied as a molecular tool for gene therapy and gene functional study. Despite its success as a live vaccine, the vaccination causes some mild to serious bur rare adverse events in vaccinees such as generalized Vaccinia and encepharitis. Therefore, identification of virulence genes and removal of these genes to create a safer vaccine remain an important tasks. In this study, the author seeks to elucidate the possible relationship between immune evading proteins E3 and B19. VV did not allow double deletions of E3 and B19, indicating the existence of a relationship between the two genes.
ContributorsBarclay, Shizuka (Author) / Jacobs, Bertram (Thesis director) / Ugarova, Tatiana (Committee member) / Kibler, Karen (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Although the number of women earning college degrees and entering the workforce is increasing, a gender gap persists at top leadership positions. Women are faced with numerous challenges throughout the talent pipeline, challenges that often drive women out of the workforce. This paper looks at the power of mentoring and how women, particularly young women, have the potential to overcome these challenges through a successful mentoring relationship. We use examples of successful mentoring programs at the corporate and university level to support the development of a mentoring program at the high school level. Our paper presents the research and development process behind the Young Women in Leadership (YWiL) Workshop, a half-day event that focused on bringing awareness to the importance of mentoring and leadership at the high school level while providing young women with the confidence and knowledge to begin to establish their own mentoring relationships.
ContributorsRust, Brenna (Co-author) / Myers, Sheridan (Co-author) / Desch, Tim (Thesis director) / Kalika, Dale (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Accountancy (Contributor) / T. Denny Sanford School of Social and Family Dynamics (Contributor) / WPC Graduate Programs (Contributor) / W. P. Carey School of Business (Contributor)
Created2015-05