Microbiology Commons^™

Treponema Denticola Synthesizes C-Di-Amp And Encodes The Cdaa-Type Diadenylate Cyclase Cdaa, Claire R. O'Brien

Theses and Dissertations

Periodontitis is a form of oral disease characterized by dysbiosis of the oral microbiome, leading to inflammation, bone resorption, and in severe cases, entire tooth loss, affecting 42% of adults in the US. One of the bacteria most associated with periodontal disease progression is Treponema denticola (Td), an oral spirochete which inhabits the mouth in small quantities during health but which can dominate the biofilms that form during periodontal disease. The ability of Td to survive in a disease environment and contribute to the progression of disease requires the use of robust signaling networks. Analysis of Td cultures …

Optimized Selenium Status, Gut Microbiota, And Type 2 Diabetes, Ying-Chen Huang

Theses and Dissertations

We have previously demonstrated that long-term dietary Se deficiency in old Terc^-/- mice with humanized telomeres induces type-2 diabetes and exacerbates age-dependent increases in the abundance of A. muciniphila and Lachnospiraceae, which are related to obesity and metabolic syndromes. The objectives of this dissertation are: 1) to determine the minimum intake of Se required for type 2 diabetes prevention in middle-aged mice; 2) to evaluate the efficacy of A. muciniphila and R. torques (a Lachnospiraceae family member) to intervene dietary Se deficiency-induced type 2 diabetes and the underlying mechanisms; 3) to assess sex differences in the responses to …

Insights Into Halophilic Microbial Adaptation: Analysis Of Integrons And Associated Genomic Structures And Characterization Of A Nitrilase In Hypersaline Environments, Sarah Sonbol

Theses and Dissertations

Hypersaline environments are extreme habitats that can be exploited as biotechnological resources. Here, we characterized a nitrilase (NitraS-ATII) isolated from Atlantis II Deep brine pool. It showed higher thermal stability and heavy metal tolerance compared to a closely related nitrilase.

We also studied integrons in halophiles and hypersaline environments. Integrons are genetic platforms in which an integron integrase (IntI) mediates the excision and integration of gene cassettes at specific recombination sites. In order to search for integrons in halophiles and hypersaline metagenomes, we used a PCR-based approach, in addition to different bioinformatics tools, mainly IntegronFinder.

We found that integrons and …

Uncovering Potential Biofilm Modulators, Liliana Margent

Theses and Dissertations

Biofilms have negative and positive impacts depending on the context they develop. In this work, I optimized a biofilm assay to evaluate the effect of three different types of compounds indole derivatives, 2,5 Diketopiperazines, and 12-hydroxystearic acid on the biofilm formation of E. coli.

A Mechanistic Investigation Of Cytochrome C Nitrite Reductase Catalyzed Reduction Of Nitrite To Ammonia: The Search For Catalytic Intermediates, Shahid Shahid

Theses and Dissertations

Cytochrome c Nitrite Reductase (ccNiR) is a periplasmic homodimeric decaheme enzyme that catalyzes the reduction of nitrite to ammonium in a process that involves six electrons and eight protons. Under standard assay conditions, which use a strong reducing agent as an electron source, catalysis takes place rapidly without producing detectable intermediates. However, intermediates do accumulate when weaker reducing agents are employed, allowing the ccNiR mechanism to be studied. Herein, the early stages of Shewanella oneidensis ccNiR-catalyzed nitrite reduction were investigated in isolation by using the weak reducing agents N,N,N’,N’-tetramethyl-p-phenylenediamine (TMPD) and the 2-electron reduced form of indigo trisulfonate. Experiments were …

Understanding The Role Of Protein Kinases Kin1 And Kin2 In The Protein Folding Pathways In The Yeast Saccharomyces Cerevisiae, Chandrima Ghosh

Theses and Dissertations

Eukaryotic protein kinases catalyze the transfer of the -phosphate of an ATP to a serine/threonine/tyrosine residue present in a protein substrate. The phosphorylation of proteins has profound effects on their activity and protein-protein interactions, thus regulating a plethora of cellular processes, including cell growth, differentiation and protein homeostasis (or proteostasis). Our lab is the first to demonstrate that protein kinases Kin1 and its paralog Kin2 in the budding yeast Saccharomyces cerevisiae, orthologs of human microtubule affinity-regulating kinase (MARK), contribute to protein-folding homeostasis inside the endoplasmic reticulum (ER), in addition to their canonical roles in cellular exocytosis. The main aim of …

Alternative Pathway For Provision Of Acyl Coa Precursors For Fatty Acid Biosynthesis: Purification And Kinetic Characterization Of Phosphotransbutyrylase And Butyrate Kinase From Listeria Monocytogenes, Sirisha Sirobhushanam

Theses and Dissertations

Listeria monocytogenes is a foodborne pathogen that causes listeriosis, a disease characterized by gastroenteritis, meningitis, spontaneous miscarriages and high mortality rate among infected individuals. L. monocytogenes is a major concern in the food industry, due to its ability to grow at refrigeration temperatures and the zero tolerance policy of the FDA, resulting in expensive food recalls. Growth at low temperatures is aided in part by the high membrane content of branched-chain fatty acids (BCFAs) which imparts greater fluidity to the membrane. Mutants of L. monocytogenes impaired in BCFA biosynthesis display diminished growth at normal and low temperatures, exhibit lower tolerance …

Elucidation Of A Novel Pathway In Staphylococcus Aureus: The Essential Site-Specific Processing Of Ribosomal Protein L27, Erin A. Wall

Theses and Dissertations

Ribosomal protein L27 is a component of the eubacterial large ribosomal subunit that has been shown to play a critical role in substrate stabilization during protein synthesis. This function is mediated by the L27 N-terminus, which protrudes into the peptidyl transferase center where it interacts with both A-site and P-site tRNAs as well as with 23S rRNA. We observed that L27 in S. aureus and other Firmicutes is encoded with a short N-terminal extension that is not present in most Gram-negative organisms, and is absent from mature ribosomes. The extension contains a conserved cleavage motif; nine N-terminal amino acids are …

Characterization Of A Novel Protease In Staphylococcus Aureus, Adam L. Johnson

Theses and Dissertations

A newly discovered cysteine protease, Prp, has been shown to perform an essential, site-specific cleavage of ribosomal protein L27 in Staphylococcus aureus. In Firmicutes and related bacteria, ribosomal protein L27 is encoded with a conserved N-terminal extension that must be removed to expose residues critical for ribosome function. Uncleavable and pre-cleaved variants were unable to complement an L27 deletion in S. aureus, indicating that this N-terminal processing event is essential and likely plays an important regulatory role. The gene encoding the responsible protease (prp) has been shown to be essential, and is found in all organisms …

Enzyme Activity, Maturation And Regulation Of Anaerobic Reductases In Shewanella Oneidensis Mr-1, Kenneth L. Brockman

Theses and Dissertations

Shewanella oneidensis MR-1 is a metal-reducing bacterium capable of using a wide range of terminal electron acceptors. These include oxygen, metal oxides and organic compounds such as dimethyl sulfoxide (DMSO) and fumarate. In addition, several nitrogen and sulfur based compounds can be used as terminal electron acceptors, including sulfite, for which the terminal reductase was recently identified as an octaheme c-type cytochrome that contains an atypical heme binding site. In this study, several additional components involved in sulfite reduction were identified. These include SirCD that form a membrane-bound electron-transferring complex with SirA, SirBI that appear to be involved in protein …

A Synthetic Biology Approach To Engineering New Anticancer Agents, Shane Robert Wesener

Theses and Dissertations

Histone deacetylase (HDAC) inhibitors are becoming increasingly valuable therapeutic agents in treatment of several types of malignancies. FK228 is a depsipeptde anticancer compound produced by Chromobacterium violaceum no. 968 through a nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) hybrid assembly line. In the present study, reconstitution of the biosynthetic pathway responsible for the production of FK228 revealed cross-talk between modular PKS and fatty acid synthase. This pathway contains two PKS modules on the DepBC enzymes that lack a functional acyltransferase (AT) domain, and no apparent AT-encoding gene exists within the gene cluster or its vicinity. We reported through heterologous expression of …

Cellular Metabolism And Its Effect On The Type Iii Secretion System Of Dickeya Dadantii 3937, William Cortrell Hutchins

Theses and Dissertations

Nutrition, in both eukaryotes and prokaryotes, is vital to the life and well-being of the species. In organisms such as Escherichia coli, metabolism and its regulation have been well established, whereas in Dickeya dadantii 3937, the metabolic pathways and their effects on other processes have not been elucidated. Little is known is how carbon metabolism is able to regulate virulence and pathogenicity in this organism. In this work, we have investigated how the metabolic network contributes to positively and negatively regulating the pathogenicity of Dickeya dadantii 3937.

Chapter 1 provides an overview of the history and virulence processes in …

Lipids Of Fungal Spores, Identification And Metabolism, Jim L. Bushnell

Theses and Dissertations

The lipids of the spores of the Basidiomycetes: Ustilago bullata, Lycoperdon perlatum and Calvatia gigantea were investigated. The spores of U. bullata were found to have hydrocarbons ranging from C_9 to C_24, methyl esters of fatty acids ranging from C_14 to C_24, and free fatty acids from C_14 to C_24. The spores of L. perlatum were found to have few hydrocarbons (C_22 being the predominent one); no methyl esters were detected and the fatty acids were from C_15 to C_18. Long chain aldehydes (C_30) were also detected in low concentration. At the ultrastructural level the Lycoperdon spores were found to …