Matching Items (96)
Filtering by
- All Subjects: Biology
- All Subjects: Microbiology
- Creators: School of Life Sciences
Description
The prevalence of antibiotic resistant bacterial pathogens has increased since the introduction of penicillin in the 1940s. Insufficient development of novel antibacterial agents is leaving us with a failing arsenal of therapies to combat these pathogenic organisms. We have identified a clay mineral mixture (designated CB) that exhibits in vitro antibacterial activity against a broad spectrum of bacterial pathogens, yet the antibacterial mechanism of action remains unknown. Antibacterial susceptibility testing of four different clay samples collected from the same source revealed that these natural clays had markedly different antibacterial activity. X-ray diffraction analyses of these minerals revealed minor mineralogical differences across the samples; however, ICP analyses demonstrated that the concentrations of many elements, Fe, Co, Cu, Ni, and Zn in particular, vary greatly across the four clay mixture leachates. Supplementation of a non-antibacterial leachate containing lower concentrations of Fe, Co, Ni, Cu, and Zn to final ion concentrations and a pH equivalent to that of the antibacterial leachate resulted in antibacterial activity against E. coli and MRSA, confirming the role of these ions in the in vitro antibacterial clay mixture leachates. The prevailing hypothesis is that metal ions participate in redox cycling and produce ROS, leading to oxidative damage to macromolecules and resulting in cellular death. However, E. coli cells showed no increase in DNA or protein oxidative lesions and a slight increase in lipid peroxidation following exposure to CB-L. Supplementation of CB-L with ROS scavengers eliminated oxidative damage in E. coli, but did not rescue the cells from killing, indicating that in vitro killing is due to direct metal toxicity and not to indirect oxidative damage. Finally, we ion-exchanged non-antibacterial clays with Fe, Co, Cu, and Zn and established antibacterial activity in these samples. Treatment of MRSA skin infections with both natural and ion-exchanged clays significantly decreased the bacterial load after 7 days of treatment. We conclude that 1) in vitro clay-mediated killing is due to toxicity associated directly with released metal ions and not to indirect oxidative damage and 2) that in vivo killing is due to the physical properties of the clays rather than metal ion toxicity.
ContributorsOtto, Caitin Carol (Author) / Haydel, Shelley (Thesis advisor) / Stout, Valerie (Committee member) / Roberson, Robby (Committee member) / Sandrin, Todd (Committee member) / Rege, Kaushal (Committee member) / Arizona State University (Publisher)
Created2014
Description
Vitellogenin (vg) is a precursor protein of egg yolk in honeybees, but it is also known to have immunological functions. The purpose of this experiment was to determine the effect of vg on the viral load of deformed wing virus (DWV) in worker honey bees (Apis mellifera). I hypothesized that a reduction in vg expression would lead to an increase in the viral load. I collected 180 worker bees and split them into four groups: half the bees were subjected to a vg gene knockdown by injections of double stranded vg RNA, and the rest were injected with green fluorescent protein (gfp) double stranded RNA. Half of each group was thereafter injected with DWV, and half given a sham injection. The rate of mortality in all four groups was higher than expected, leaving only 17 bees total. I dissected these bees' fat bodies and extracted their RNA to test for vg and DWV. PCR results showed that, out of the small group of remaining bees, the levels of vg were not statistically different. Furthermore, both groups of virus-injected bees showed similar viral loads. Because of the high mortality rate bees and the lack of differing levels of vg transcript between experimental and control groups, I could not draw conclusions from these results. The high mortality could be caused by several factors: temperature-induced stress, repeated stress from the two injections, and stress from viral infection. In addition, it is possible that the vg dsRNA batch I used was faulty. This thesis exemplifies that information cannot safely be extracted when loss of sampling units result in a small datasets that do not represent the original sampling population.
ContributorsCrable, Emma Lewis (Author) / Amdam, Gro (Thesis director) / Wang, Ying (Committee member) / Dahan, Romain (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
Triops (Branchiopoda: Notostraca) and Streptocephalus (Branchiopoda: Anostraca) are two crustaceans which cohabitate in ephemeral freshwater pools. They both lay desiccation resistant eggs that disperse passively to new hydrologically isolated environments. The extent of genetic distance among regions and populations is of perennial interest in animals that live in such isolated habitats. Populations in six natural ephemeral pool habitats located in two different regions of the Sonoran Desert and a transition area between the Sonoran and Chihuahuan Deserts were sampled. Sequences from Genbank were used for reference points in the determination of species as well as to further identify regional genetic distance within species. This study estimated the amount of within and between genetic distance of individuals from each region and population through the use of a neutral marker, cytochrome oxidase I (COI). We concluded that, although the method of passive dispersal may differ between the two genera, the differences do not results in different patterns of genetic distances between regions and populations. Furthermore, we only found the putative species, Triops longicaudatus "short", with enough distinct speciation. Although Triops longicaudatus "long" and Triops newberryi may be in the early stages of speciation, this study does not find enough support to conclude that they have separated.
ContributorsMurphy Jr., Patrick Joseph (Author) / Rutowski, Ronald (Thesis director) / Cartwright, Reed (Committee member) / Lessios, Nikos (Committee member) / School of Life Sciences (Contributor) / School of Human Evolution and Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
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
Cystic Fibrosis (CF) is a genetic disorder that disrupts the hydration of mucous of the lungs, which promotes opportunistic bacterial infections that begin in the affected person’s childhood, and persist into adulthood. One of the bacteria that infect the CF lung is Pseudomonas aeruginosa. This gram-negative bacterium is acquired from the environment of the CF lung, changing the expression of phenotypes over the course of the infection. As P. aeruginosa infections become chronic, some phenotype changes are known to be linked with negative patient outcomes. An important exoproduct phenotype is rhamnolipid production, which is a glycolipid that P. aeruginosa produces as a surfactant for surface-mediated travel. Over time, the expression of this phenotype decreases in expression in the CF lung.
The objective of this investigation is to evaluate how environmental changes that are related to the growth environment in the CF lung alters rhamnolipid production. Thirty-five P. aeruginosa isolates from Dartmouth College and Seattle Children’s Hospital were selected to observe the impact of temperature, presence of Staphylococcus aureus metabolites, and oxygen availability on rhamnolipid production. It was found that the rhamnolipid production significantly decreased for 30C versus 37C, but not at 40C. The addition of S. aureus spent media, in any of the tested conditions, did not influence rhamnolipid production. Finally, the change in oxygen concentration from normoxia to hypoxia significantly reduced rhamnolipid production. These results were compared to swarming assay data to understand how changes in rhamnolipid production impact surface-mediated motility.
The objective of this investigation is to evaluate how environmental changes that are related to the growth environment in the CF lung alters rhamnolipid production. Thirty-five P. aeruginosa isolates from Dartmouth College and Seattle Children’s Hospital were selected to observe the impact of temperature, presence of Staphylococcus aureus metabolites, and oxygen availability on rhamnolipid production. It was found that the rhamnolipid production significantly decreased for 30C versus 37C, but not at 40C. The addition of S. aureus spent media, in any of the tested conditions, did not influence rhamnolipid production. Finally, the change in oxygen concentration from normoxia to hypoxia significantly reduced rhamnolipid production. These results were compared to swarming assay data to understand how changes in rhamnolipid production impact surface-mediated motility.
ContributorsKiermayr, Jonathan Patrick (Author) / Bean, Heather (Thesis director) / Misra, Rajeev (Committee member) / Haydel, Shelley (Committee member) / School of International Letters and Cultures (Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The Beauty Within is a ceramics show displaying human body anatomy, which seeks to bridge aspects of my biological sciences major in the School of Life Sciences with aspects of my studio art minor in the Herberger Institute for Design and the Arts. My goal in creating the show was to change the opinion of people on human body organs from unease to admiration by recreating these organs in an artistic light. By stylizing the construction of the pieces and bringing in the contemporary form of art \u2014 makeup art \u2014 I hoped to bring a new light to the pieces and highlight the beauty within the human body. By leaving the pieces partly unfinished I further hoped to draw attention to the natural beauty within the pieces regardless of the makeup that covers them. By holding the show in the human anatomy lab room on campus and having both animal and human organs on display I was able to create that sense of disgust toward the organs in the viewers. The beauty of my created pieces was then directly contrasted with the disgust felt about the real organs by displaying each of my pieces next to a real organ. The reactions of the viewers reflected a change in view from the actual organs to my re-created organs, and therefore the goal of the show was achieved.
ContributorsThomas, Brandon Lee (Author) / Weiser, Kurt (Thesis director) / Chung, Samuel (Committee member) / School of Art (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
This study focused on the connection between the EnvZ/OmpR two-component regulatory system and the iron homeostasis system in Escherichia coli, specifically how a mutant form of EnvZ11/OmpR is able to reduce the expression of fepA::lacZ, a reporter gene fusion in E. coli. FepA is one of several outer membrane siderophore receptors that allow extracellular siderophores bound to iron to enter the cells to power various biological processes. Previous studies have shown that in E. coli cells that expressed a mutant allele of envZ, called envZ11, which led to altered expression of various iron genes including down regulation of fepA::lacZ. The wild type EnvZ/OmpR system is not considered to regulate iron genes, but because these envz11 strains had downregulated fepA::lacZ, this study was undertaken to understand the connection and mechanisms of this downregulation. A large number of Lac+ revertants were obtained from the B32-2483 strain (envz11 and fepA::lacZ) and 7 Lac+ revertants that had reversion mutations not directly correcting the envZ11 allele were further characterized. With P1 phage transduction genetic mapping that involved moving a kanamycin resistance marker linked to fepA::lacZ, two Lac+ revertants were found to have their reversion mutations in the fepA promoter region, while the other five revertants had their mutations mapping outside the fepA region. These two revertants underwent DNA sequencing and found to carry two different single base pair mutations in two different locations of the fepA promoter region. Each one is in the Fur repressor binding region, but one also may have affected the Shine-Dalgarno region involved in translation initiation. All 7 reveratants underwent beta-galactosidase assays to measure fepA::lacZ expression. The two revertants that had mutations in the fepA promoter region had significantly increased fepA activity, with the revertant with the Shine-Dalgarno mutation having the most elevated fepA expression. The other 5 revertants that did not map in the fepA region had fepA expression elevated to the same level as that found in the wild type EnvZ/OmpR background. The data suggest that the negative effect of envZ11 can be overcome by multiple mechanisms, including directly correcting the envZ11 allele or changing the fepA promoter region.
ContributorsKalinkin, Victor Arkady (Co-author) / Misra, Rajeev (Co-author, Thesis director) / Mason, Hugh (Committee member) / Foy, Joseph (Committee member) / Biomedical Informatics Program (Contributor) / School of Life Sciences (Contributor) / W. P. Carey School of Business (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