Life Sciences Commons^™

Quantitative Analysis And Imaging-Based Insights Into The Characteristics And Mechanisms Of Yeast Pattern Formation, Lin Chen

Dissertations & Theses (Open Access)

Biofilm formation is a common lifestyle adapted by bacteria and fungi in response to various environmental stresses. Bacterial and fungal biofilms adhering to medical devices convey resistance to antibiotics or biocides, causing high rates of clinical infections. Microorganisms are protected from harsh environmental conditions by reduced stress penetration through the complex biofilm architecture with distinct patterns. Although the molecular regulations of surface patterning have been well characterized in bacteria, the mechanisms underlying the complex pattern formation in eukaryotic biofilms remain unclear.

This dissertation aims to investigate the salient features of robust colony expansion in yeast biofilms and the processes driving …

Large-Scale Identification Of Chemically Induced Mutations In Drosophila Melanogaster., Nele A Haelterman, Lichun Jiang, Yumei Li, Vafa Bayat, Hector Sandoval, Berrak Ugur, Kai Li Tan, Ke Zhang, Danqing Bei, Bo Xiong, Wu-Lin Charng, Theodore Busby, Adeel Jawaid, Gabriela David, Manish Jaiswal, Koen J T Venken, Shinya Yamamoto, Rui Chen, Hugo J Bellen

Faculty Publications

Forward genetic screens using chemical mutagens have been successful in defining the function of thousands of genes in eukaryotic model organisms. The main drawback of this strategy is the time-consuming identification of the molecular lesions causative of the phenotypes of interest. With whole-genome sequencing (WGS), it is now possible to sequence hundreds of strains, but determining which mutations are causative among thousands of polymorphisms remains challenging. We have sequenced 394 mutant strains, generated in a chemical mutagenesis screen, for essential genes on the Drosophila X chromosome and describe strategies to reduce the number of candidate mutations from an average of …

Potential Roles Of Peroxidases In Caenorhabditis Elegans Innate Immunity, George R. Tiller, George R. Tiller

Dissertations & Theses (Open Access)

The production of ROS (reactive oxygen species) in response to pathogen detection is a rapid, nonspecific response that is evolutionarily conserved from nematodes to humans. ROS serve as direct and indirect effectors of innate and adaptive immunity. In Caenorhabditis elegans, a ROS burst is observed during infection and is mediated by the dual oxidase BLI-3, which produces H₂O₂. RNAi (RNA interference) to reduce the amount of BLI-3 results in a significant increase in susceptibility to pathogens, suggesting BLI-3 has a role in the immune response. However, H₂O₂ by itself is not a …

Regulators Of Bacterial Cell Division: Investigations Of Min Oscillation And Ftsa Activity, Jennifer R. Herricks

Dissertations & Theses (Open Access)

Cytokinesis is a fundamental process that is essential for bacterial proliferation. The cytokinetic machinery in bacteria is termed the “divisome”. The divisome is a complex of proteins that forms a ring at midcell over dividing nucleoids. In order for daughter cells to form, the divisome must constrict. As constriction occurs, two new cell poles are formed, one for each daughter cell. The first step in divisome formation is the assembly of FtsZ into a Z ring. The work presented in this dissertation focuses on two proteins that regulate the Z ring: MinD, which is a part of the Min system …

Development Of Chimeric Type Iv Secretion Systems For Transfer Of Heterologous Substrates Across The Gram-Negative Cell Envelope, Trista M. Berry

Dissertations & Theses (Open Access)

Many bacteria use Type IV Secretion Systems (T4SSs) to aid in pathogenesis by translocating virulence factors across the cell envelope and into eukaryotic cells. These systems are structurally and functionally diverse, but are often compared to the archetypal VirB/VirD4 T4SS of Agrobacterium tumefaciens. This system is composed of the VirD4 type IV coupling protein (T4CP) and 11 VirB subunits (VirB1-11) that assemble as the secretion channel and an extracellular pilus. The T4CP is an inner membrane ATPase that interacts with T4SS substrates and the secretion channel, and is thought to link substrates with the secretion channel and possibly energize …

Energy Stress Causes Chaperones To Assemble Into Cytoplasmic Complexes, Kimberly J. Cope

Dissertations & Theses (Open Access)

The majority of proteins require molecular chaperones to assist their folding into tertiary and quaternary structures. Certain stresses can compromise the weak hydrophobic forces responsible for these structures and lead to protein unfolding, misfolding, and aggregation. Aggregates of proteins are hallmarks of devastating diseases such as Alzheimer’s, Parkinson’s, and Huntington’s diseases. Fortunately, bacteria, plants, and fungi have a potent disaggregase, named Hsp104 in Saccharomyces cerevisiae. Recently, heat-induced aggregates, termed Q-bodies, were found to contain three molecular chaperones: Hsp70, Hsp104, and Hsp42. Their coalescence from small puncta into larger inclusions required Hsp104. During glucose deprivation, a stress that isn’t known to …

Development Of A Molecular Gram-Stain Assay For The Diagnosis Of Blood Stream Infections Associated With Sepsis, Douglas Bryan Litwin

Dissertations & Theses (Open Access)

Sepsis is a serious medical condition resulting from the severe dysregulation of the immune response that is generally triggered by infection. It affects more than 1.1 million Americans, has an average mortality rate of 30%, and is estimated to cost $24.3 billion annually. Currently, blood culture followed by Gram-stain analysis is the gold standard for diagnosing bacterial infections associated with sepsis. This method generates a high rate of false negative results and, in general, requires 20 to 48 hr to provide results. Both of these problems are related to the requirement that the bacterial pathogens grow under defined laboratory conditions. …

Regulation Of The Candida Albicans Arginine Biosynthetic Pathway, Claudia Jimenez Lopez

Dissertations & Theses (Open Access)

Candida albicans is the most importan thuman-associatedfungus.It is a commensal microorganism but also an opportunistic pathogen able to cause superficial infections aswellaslife-threateninginfectionswhich are associated with a highmortalityrateof 50%. The interactions between C. albicans and the cells of the mammalian innate immune system, which confer the most important protecting mechanisms against disseminated infections, are very dynamic and determine the success of C. albicans as a pathogen. Transcriptional profiling has shown that phagocytosis of C. albicans by macrophages results primarily in the activation of alternative carbon metabolism pathways suggesting that the pathogen is exposed to a glucose poor environment. Changes in …

Functional Analysis Of Cytosolic Hsp70 Nucleotide Exchange Factor Networks In Yeast, Jennifer Lynn Abrams

Dissertations & Theses (Open Access)

The Hsp70 class of molecular chaperones play critical roles in protein homeostasis via an ATP-dependent folding cycle. Cytosolic Hsp70s in the budding yeast Saccharomyces cerevisiae, Ssa and Ssb, interact with up to three distinct nucleotide exchange factors (NEFs) homologous to human counterparts; Sse1/Sse2/HSP110, Fes1/HspBP1, and Snl1/Bag1. In an effort to understand the differential functional contributions of the cytosolic NEFs to protein homeostasis (“proteostasis”), I carried out comparative genetic, biochemical and cell biological analyses. For these studies, I developed protocols to monitor protein disaggregation and reactivation in a near real-time coupled assay that revealed the importance of aggregate dynamics in the …

Characterization Of Ftsa-Ftsn Interaction During Escherichia Coli Cell Division, Kimberly.Busiek@Gmail.Com K. Busiek

Dissertations & Theses (Open Access)

Division of a bacterial cell into two equal daughter cells requires precise assembly and constriction of the division machinery, or divisome. The Escherichia coli divisome includes nearly a dozen essential cell division proteins that assemble at midcell between segregating sister chromosomes. FtsZ, a homolog of eukaryotic tubulin, is the first essential cell division protein to localize at midcell where it polymerizes into a ring-shaped scaffold (Z ring). Establishment of the Z ring is required for recruitment of downstream cell division proteins including FtsA, a cytoplasmic protein that tethers the Z ring to the inner membrane. Following localization of FtsA and …