Microbial Physiology Commons^™

Coordinating The Layers: Regulation Of Peptidoglycan Synthesis And Cell Wall Assembly In Mycobacterium Smegmatis By Murj And Pgfa, Karen Emmanuella Samaga-De-Tembiwa

Biology Dissertations

The mycobacterial cell envelope consists of three covalently linked layers whose synthesis must be coordinated to maintain structural integrity during polar growth. While the biosynthetic enzymes for each layer are well characterized, the molecular mechanisms that coordinate synthesis across layers have remained poorly understood. This thesis investigates two essential transmembrane proteins, PgfA and MurJ, that regulate peptidoglycan metabolism in Mycobacterium smegmatis and provide new insight into how mycobacteria synchronize cell wall assembly.

We present evidence that PgfA functions as a bifunctional regulator that links peptidoglycan metabolism to the availability of trehalose monomycolate (TMM), a key mycolic acid precursor. Through epistasis …

The Role Of Horizontal Gene Transfer In Antibiotic Resistance Amidst Prevalent Community And Healthcare-Associated Mrsa Rates, Gabrielle Nascimento

Honors College Theses

In recent decades, cases of community-acquired MRSA (CA-MRSA) and healthcare-associated MRSA (HA-MRSA) have been on the rise. The ability of antibiotic resistance to transfer between microorganisms greatly expands its threat to the effective treatment and containment of bacterial infections. The mecA gene is found on a mobile cassette within the Staphylococcal cell and encodes for PBP2a, an alternate version of penicillin-binding protein (PBP) with less binding affinity for β-lactam antibiotics, increasing resistance to the effects of antibiotics. The goal of this research is to investigate the horizontal transfer of the mecA gene between various Staphylococcus species as well as to …

The Physiological Significance Of Nitric Oxide Synthase In Staphylococci, Ryan M. Singh

Theses & Dissertations

Staphylococci, particularly Staphylococcus epidermidis, are common causes of implant-associated infections that may result in notable morbidity and mortality. One of the ways the innate immune system attempts to combat these invading pathogens is via the respiratory burst, in which free radical species such as nitric oxide (NO^•), toxic to bacterial respiration, are released in large quantities. Despite the toxicity of NO^•, some bacteria, including staphylococci, encode an endogenous bacterial nitric oxide synthase (bNOS), whose physiological role has been unclear until now. In this dissertation, we demonstrate that S. epidermidis is able to overcome the toxicity …

Characterizing The Role Of Pa5189 Of Pseudomonas Aeruginosa In Deletion And Overexpression Mutants, Seh Na Mellick

Theses/Capstones/Creative Projects

In the context of rising multidrug resistance in biofilm-forming pathogens like Pseudomonas aeruginosa, this study investigates the role of the understudied transcription factor PA5189 in antibiotic resistance and biofilm formation. PA5189 deletion and overexpression mutants were created in a parent P. aeruginosa strain using pEX18Tc-based recombinant suicide vectors, with genotypic verification of putative triparental conjugants achieved through restriction digestion and PCR. The study revealed that PA5189 overexpression significantly increases resistance to commonly used broad spectrum antibiotics such as ciprofloxacin and imipenem. Additionally, differential expression of PA5189 was found to notably affect biofilm formation, with variations contingent on the nutrient …

Managing Stress: A Study Of Stress Response Mechanisms In Mycobacteria, Augusto C. Hunt Serracin

Biology Dissertations - Archive

Mycobacteria encompass many pathogenic species known to cause severe disease in humans. A well-known example is Mycobacterium tuberculosis (Mtb), the causative agent of the lung disease tuberculosis, which kills millions of humans worldwide yearly. Pathogenic mycobacteria like Mtb are challenging to treat because of their innate ability to adapt to environmental stress. Their unique cell physiology and conserved stress responses allow them to combat biological insults, regulate growth, and regulate genes involved in stress; all these responses increase tolerance to antibiotics. The current therapies to treat mycobacterial infections are lengthy and, at times, unsuccessful, partly due to antibiotic tolerance. A …

Contributions Of The Replication Initiator Protein Dnaa To Physiology And Virulence Of The Lyme Disease Spirochete, Andrew Krusenstjerna

Theses and Dissertations--Microbiology, Immunology, and Molecular Genetics

Borrelia burgdorferi, the etiological agent of Lyme disease, is the most prevalent vector-borne disease in the United States. The spirochetal population is naturally maintained by consistently cycling between Ixodid ticks and small vertebrates. To survive within these diverse niches, B. burgdorferi has evolved a unique physiology and regulatory network to sense and respond to environmental fluxes. Replication is a hallmark of the Lyme spirochete’s enzootic life cycle, specifically at the nymphal tick-to-vertebrate interface. The mechanisms and regulatory schema for the basic cellular processes in B. burgdorferi, or indeed any member of the phylum spirochaetota, are largely unknown. The central hypothesis …

Characterizing The Regulation Of Candida Albicans Hyphal Morphogenesis In The Context Of Host Macrophages, Hannah Wilson

Dissertations and Theses (Open Access)

Candida albicans is a commensal fungus that resides on the skin, mucosal surfaces, and in the gut of an estimated 80% of individuals. Though generally harmless, C. albicans is capable of causing uncomfortable mucosal infections as well as deadly disseminated infections depending on the immune status of the host. Although antifungal therapeutics exist, the mortality rate associated with disseminated disease still lingers around 50%. Further, C. albicans is the fourth most common cause of all bloodstream infections and continues to present as a major clinical issue with less than satisfactory treatment options. For this reason, it is imperative to understand …

Understanding The Role Of Heterodisulfide Reductase During Nitrogen Fixation By Methanosarcina Acetivorans, Grant Shelnut

Biological Sciences Undergraduate Honors Theses

Methanosarcina acetivorans is a methanogenic archaeon (methanogen) that is important for several processes in our biosphere. A feature of interest within this methanogen is the enzyme nitrogenase which catalyzes the reduction of unusable dinitrogen gas (N₂) into a usable form of nitrogen, ammonia (NH₃). How electrons are transferred within M. acetivorans to nitrogenase during N₂ reduction is unknown. Heterodisulfide reductase (Hdr) is a key enzyme known to reduce the electron carrier protein ferredoxin, which is a direct electron donor to nitrogenase in bacteria. I hypothesized that cytoplasmic HdrA2B2C2 functions in electron transfer to nitrogenase and …

Characterization Of Genetic Pathways Involved In Resistance To A Novel Antifungal Peptide, Kayla L. Haberman

Graduate Theses and Dissertations

Antibiotic resistance is increasing prevalence, particularly in Candida glabrata. This opportunistic pathogen is closely phylogenetically related to Saccharomyces cerevisiae; however, its characterization is limited. C. glabrata is only second to Candida albicans as a fungal pathogen in immunocompromised patients. Commonly resistant to azoles, the most common fungal therapy, it has become costly and challenging to treat. A histatin 5 derived antifungal peptide, KM29, has a high degree of efficacy in Candida species and S. cerevisiae. The objective of this work is to advance our understanding of the mechanism of action of KM29 against C. glabrata. Previous work in the lab …

Functional Characterization Of A Putative Alternative Oxidase In Sporisorium Reilianum F. Sp. Zeae., Emma A Lamb

College of Arts & Sciences Senior Theses

Sporisorium reilianum is a pathogenic basidiomycete fungus with two formae speciales, each capable of infecting corn (SRZ) or sorghum (SRS), respectively. This fungus is also a dimorphic variety, meaning it can switch between its haploid, yeast-like sporidia and diploid teliospore stages over the course of its life cycle (Schirawski). When S. reilianum is found in a haploid state and conditions are favorable, it will mate with a compatible non-self mating type to begin filamentous growth and proliferation in the plant host (Zhao). S. relianum, like most fungi, utilizes the four classical components of the electron transport chain to produce …

Characterization Of Streptomyces Nymphaeiformis Sp. Nov., And Its Taxonomic Relatedness To Other Polyhydroxybutyrate-Degrading Streptomycetes, Gary R. Hix, Muhammad S. Khan, Mikayla T. Miller, Elisha C. Napier, Allison L. O'Brien, Roger P. White, Stephen F. Baron Ph.D.

Biology Faculty Scholarship

A polyhydroxybutyrate (PHB)-degrading actinomycete, strain SFB5A^T, was identified as a species of Streptomyces based on its membrane fatty acid profile and the presence of LL-diaminopimelic acid in the cell wall. It formed sporulating mycelia on most agar media, but flat or wrinkled, moist colonies on trypticase soy agar. Spores were smooth, cylindrical, and borne on long, straight to flexuous chains. It produced a light brown diffusible pigment, but not melanin. Comparison of genomic digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values indicated that strain SFB5A^T was related to Streptomyces litmocidini JCM 4394^T , Streptomyces …

An Integrative Investigation Of The Synechococcus A/B Clade During Adaptive Radiation At The Upper Thermal Limit Of Phototrophy, Christopher L. Pierpont

Graduate Student Theses, Dissertations, & Professional Papers

Thermophilic microorganisms have been scientifically observed since the early nineteenth century and have spurred many questions about the limits of life and the capacity of organisms to survive extreme conditions. Decades of research on thermophile proteins and genomes have yielded several proposed correlates of temperature that may contribute to adaptation of bacteria and archaea to high temperature. However, many of the generalizations reported are drawn from analyses of deeply divergent taxa or from individual case studies in isolation from mesophilic relatives. Members of the Synechococcus A/B (SynAB) group are the only cyanobacteria with members able to grow above 65 °C …

Identification Of Proteins That Contribute To Yeast Heat Stress By Lysine Acetylation, Weijia Shi

Biological Sciences Undergraduate Honors Theses

Evidence is emerging that protein lysine acetylation may be a novel type of post-translational modification (PTM) contributing to the mechanisms of yeast heat stress responses. Proteomics studies including ours have identified over 1,000 acetylated proteins in the yeast proteomes that are composed of about 6,000 proteins. Our lab recently identified 596 proteins that underwent acetylation changes during heat shock by mass spectrometry. However, the role of lysine acetylation on specific residues of specific proteins in yeast thermotolerance remains largely unknown. This study selected 43 proteins from our lab’s previous work and examined their possible contributions to yeast heat stress responses. …

Inhibition Of Biofilm Formation By The Synergistic Action Of Egcg-S And Antibiotics, Shrameeta Shinde, Lee Lee, Tinchun Chu

Department of Biology Faculty Scholarship and Creative Works

Biofilm, a stress-induced physiological state, is an established means of antimicrobial tolerance. A perpetual increase in multidrug resistant (MDR) infections associated with high mortality and morbidity have been observed in healthcare settings. Multiple studies have indicated that the use of natural products can prevent bacterial growth. Recent studies in the field have identified that epigallocatechin gallate (EGCG), a green tea polyphenol, could disrupt bacterial biofilms. A modified lipid-soluble EGCG, epigallocatechin-3-gallate-stearate (EGCG-S), has enhanced the beneficial properties of green tea. This study focuses on utilizing EGCG-S as a novel synergistic agent with antibiotics to prevent or control biofilm. Different formulations of …

Characterizing The Physiology And Genetics Of Contact Dependent Growth Inhibiton Systems In Burkholderia Species, Alice Elizabeth Oates

Theses and Dissertations--Microbiology, Immunology, and Molecular Genetics

Contact-dependent growth inhibition (CDI) systems mediate interbacterial competition. The genes encoding these systems are widespread among Gram-negative bacteria, including Burkholderia pathogens. CDI systems of Burkholderia species are composed of two-partner secretion pathway proteins and function to deliver the toxic C-terminus of a polymorphic surface-exposed exoprotein BcpA (Burkholderia CDI protein A) to the cytoplasm of neighboring recipient bacteria upon cell-cell contact. Specific outer and inner membrane proteins facilitate BcpA translocation both out of the donor bacterium and into the recipient cell cytoplasm. Most Burkholderia species-specific CDI translocation factors in recipient cells are unknown. BcpA intoxication functions as a mechanism by …

The Role Of Manganese In Streptococcus Sanguinis, Tanya M. Puccio

Theses and Dissertations

Streptococcus sanguinis is primarily associated with oral health as a commensal bacterium. As an opportunistic pathogen, S. sanguinis is capable of colonizing heart valve vegetations, leading to the disease infective endocarditis. Previous studies from our lab have identified the high-affinity manganese transporter SsaACB as important for endocarditis virulence. The impact that manganese depletion has on S. sanguinis had never been evaluated and a secondary manganese transporter has not been identified. Thus, we employed the use of a fermentor to control large-scale growth over time and depleted manganese in an ΔssaACB mutant using a metal chelator, EDTA. The changes in …

Characterization Of Bacterial Isolates Obtained From Commercial Poultry Feed And Retail Food Using Whole Genome Sequence Analysis And Selected Biochemical Tests, Elena George Olson

Electronic Theses & Dissertations

The goals of this study is two-fold. The first part investigates bacterial isolates from commercial poultry feed and the second part deals with bacterial isolates recovered from retail food. In order to reduce pathogen contamination in poultry products identification of overall microbial populations in poultry production processing steps have always been considered an important monitoring tool for assessing sanitizer effectiveness and the corresponding responses of bacteria load levels on poultry carcasses. Bacterial isolates recovered from corn-based chicken feed were purified on aerobic plate count agar and eleven morphologically different colonies were selected for whole genome sequencing. In this part, the …

Genetic Diversity In The Leucoagaricus Cultivar Fungus Of Trachymyrmex Septentrionalis Fungus-Growing Ants, Lee Deininger

MCB Articles

No abstract provided.

How A Cell Knows Where To Divide: Oscillation Of Mind In Vivo, Colby Ferreira

Senior Honors Projects

Over two-million people in the United States are infected by antibiotic resistant bacteria each year. Of this number 23,000 die from these infections and other complications. Due to this, novel antibiotic targets are constantly being investigated. One process in prokaryotes that holds promise is cellular division. Bacterial cells grow and reproduce using a series of proteins known as the cell division machinery. This machinery enables the division of the parental cell into two identical daughter cells. The cell division machinery is similar between bacterial taxa, making it an ideal target for new classes of antibiotics. Therefore, understanding the molecular mechanisms …

Regulation Of The Tubulin Homolog Ftsz In Escherichia Coli, Monika S. Buczek

Dissertations, Theses, and Capstone Projects

Escherichia coli is a well-known pathogen, and importantly, a widely used model organism in all fields of biological sciences for cloning, protein purification, and as a model for Gram-negative bacterial species. And yet, researchers do not fully understand how this bacterium replicates and divides. Every year additional division proteins are discovered, which adds complexity to how we understand E. coli undergoes cell division. Due to their specific roles in cytokinesis, some of these proteins may be potential targets for development of antibacterials or bacteriostatics, which are much needed for fighting the current global antibacterial deficit. My thesis work focuses on …

Tumor Necrosis Factor Dynamically Regulates The Mrna Stabilome In Rheumatoid Arthritis Fibroblast-Like Synoviocytes, Konstantinos Loupasakis, David Kuo, Upneet K. Sokhi, Christopher Sohn, Bethany Syracuse, Eugenia G. Giannopoulou, Sung Ho Park, Hyelim Kang, Gunnar Rätsch, Lionel B. Ivashkiv, George D. Kalliolias

Publications and Research

During rheumatoid arthritis (RA), Tumor Necrosis Factor (TNF) activates fibroblast-like synoviocytes (FLS) inducing in a temporal order a constellation of genes, which perpetuate synovial inflammation. Although the molecular mechanisms regulating TNF-induced transcription are well characterized, little is known about the impact of mRNA stability on gene expression and the impact of TNF on decay rates of mRNA transcripts in FLS. To address these issues we performed RNA sequencing and genome-wide analysis of the mRNA stabilome in RA FLS. We found that TNF induces a biphasic gene expression program: initially, the inducible transcriptome consists primarily of unstable transcripts but progressively switches …

Environmental Changes Turn On The Sinorhizobium Melitloti Exor-Exos/Chvi (Rsi) Host Invasion Switch, Shari N. Walcott

Dissertations, Theses, and Capstone Projects

The free-living Gram-negative soil bacterium, Sinorhizobium meliloti, must switch into its host-invading form in order to infect the root hairs of the host plant, alfalfa (Medicago sativa), and establish a nitrogen-fixing symbiosis. The activation of the switch is believed to occur inside the infection chamber that is formed by curling of the root hairs. It is not fully understood what signals in the environment of the root hairs trigger and infection chamber S. meliloti to switch into a host-invading form since these signals were not extensively examined until now. This switch can be observed directly, due to …

Scanning Labyrinthulomycete Genomes For Yeast Transcription Factor Binding Site Motifs, Jackie L. Collier, Joshua Rest

Interdisciplinary Research Data

To develop broadly useful methods for the genetic manipulation of Labyrinthulomycetes (a diverse group of ubiquitous osmoheterotrophic marine protists), it is essential to understand the similarities and differences in regulation of gene expression among them. Toward this end we have used FIMO from the MEME suite (http://meme-suite.org/doc/fimo.html) to identify potential transcription factor binding sites in each of the three available genome sequences: Aplanochytrium kerguelense PBS07, Schizochytrium aggregatum ATCC 28209, and Aurantiochytrium limacinum ATCC MYA-1381

Functional Screening Of The Cronobacter Sakazakii Baa-894 Genome Reveals A Role For Prop (Esa_02131) In Carnitine Uptake, Audrey Feeney, Roy D. Sleator

Department of Biological Sciences Publications

Cronobacter sakazakii is a neonatal pathogen responsible for up to 80% of fatalities in infected infants. Low birth weight infants and neonates infected with C. sakazakii suffer necrotizing enterocolitis, bacteraemia and meningitis. The mode of transmission most often associated with infection is powdered infant formula (PIF) which, with an aw of ∼0.2, is too low to allow most microorganisms to persist. Survival of C. sakazakii in environments subject to extreme hyperosmotic stress has previously been attributed to the uptake of compatible solutes including proline and betaine. Herein, we report the construction and screening of a C. sakazakii genome bank and …

Characterization Of Ftsa-Ftsn Interaction During Escherichia Coli Cell Division, [email protected] K. Busiek

Dissertations and 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 …

Transcriptome Analysis Of Listeria Monocytogenes Exposed To Biocide Stress Reveals A Multi-System Response Involving Cell Wall Synthesis, Sugar Uptake, And Motility, Aidan Casey, Edward M. Fox, Stephan Schmitz-Esser, Aidan Coffey, Olivia Mcauliffe, Kieran Jordan

Department of Biological Sciences Publications

Listeria monocytogenes is a virulent food-borne pathogen most often associated with the consumption of “ready-to-eat” foods. The organism is a common contaminant of food processing plants where it may persist for extended periods of time. A commonly used approach for the control of Listeria monocytogenes in the processing environment is the application of biocides such as quaternary ammonium compounds. In this study, the transcriptomic response of a persistent strain of L. monocytogenes (strain 6179) on exposure to a sub-lethal concentration of the quaternary ammonium compound benzethonium chloride (BZT) was assessed. Using RNA-Seq, gene expression levels were quantified by sequencing …

Gata-Family Transcription Factors In Magnaporthe Oryzae, Cristian F. Quispe

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The filamentous fungus, Magnaporthe oryzae, responsible for blast rice disease, destroys around 10-30% of the rice crop annually. Infection begins when the specialized infection structure, the appressorium, generates enormous internal turgor pressure through the accumulation of glycerol. This turgor acts on a penetration peg emerging at the base of the cell, causing it to breach the leaf surface allowing its infection.

The enzyme trehalose-6- phosphate synthase (Tps1) is a central regulator of the transition from appressorium development to infectious hyphal growth. In the first chapter we show that initiation of rice blast disease requires a regulatory mechanism involving an …

Campylobacter Ureolyticus: An Emerging Gastrointestinal Pathogen?, Susan Bullman, Daniel Corcoran, James O'Leary, Brigid Lucey, Deirdre Byrne, Roy D. Sleator

Department of Biological Sciences Publications

A total of 7194 faecal samples collected over a 1-year period from patients presenting with diarrhoea were screened for Campylobacter spp. using EntericBios, a multiplex-PCR system. Of 349 Campylobacter-positive samples, 23.8% were shown to be Campylobacter ureolyticus, using a combination of 16S rRNA gene analysis and highly specific primers targeting the HSP60 gene of this organism. This is, to the best of our knowledge, the first report of C. ureolyticus in the faeces of patients presenting with gastroenteritis and may suggest a role for this organism as an emerging enteric pathogen.

The Armadillo Repeat Protein Pf16 Is Essential For Flagellar Structure And Function In Plasmodium Male Gametes, Ursula Straschil, Arthur M. Talman, David J. P. Ferguson, Karen A. Bunting, Zhengyao Xu, Elizabeth Bailes, Robert E. Sinden, Anthony A. Holder, Elizabeth F. Smith

Dartmouth Scholarship

Malaria, caused by the apicomplexan parasite Plasmodium, threatens 40% of the world's population. Transmission between vertebrate and insect hosts depends on the sexual stages of the life-cycle. The male gamete of Plasmodium parasite is the only developmental stage that possesses a flagellum. Very little is known about the identity or function of proteins in the parasite's flagellar biology. Here, we characterise a Plasmodium PF16 homologue using reverse genetics in the mouse malaria parasite Plasmodium berghei. PF16 is a conserved Armadillo-repeat protein that regulates flagellar structure and motility in organisms as diverse as green algae and mice. We show that …

Letter From The Dean, Lalit Verma

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

No abstract provided.