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Retrospective Theses and Dissertations

Microbiology

Zoology and genetics

Articles 1 - 9 of 9

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Host Regulation Of The Replication Of The Yeast Retrotransposon Ty5 , Ning Ke Jan 1997

Host Regulation Of The Replication Of The Yeast Retrotransposon Ty5 , Ning Ke

Retrospective Theses and Dissertations

The replication of retroelements may have deleterious effects on the hosts. Therefore, elements and their hosts have coevolved mechanisms to regulate retroelement replication. This regulation can occur at the transcriptional, translational, or post-translational levels as well as through targeted integration or cDNA recombination. I have studied host regulation of the Saccharomyces retrotransposon Ty5. I have found that Ty5 transcription is carefully controlled. Transcription of Ty5 is haploid specific and is repressed 10 fold in diploid strains. Ty5 transcription is also regulated by the pheromone response pathway, which is activated during mating. In addition, Ty5 transcription is regulated by flanking sequences ...


Regulation Of Brucella Abortus Catalase As A Defensive Mechanism Against Oxidative Stress , Jeonga Kim Jan 1997

Regulation Of Brucella Abortus Catalase As A Defensive Mechanism Against Oxidative Stress , Jeonga Kim

Retrospective Theses and Dissertations

Free radicals in the nature are harmful to organisms because they cause damage to tissues, cell membranes, proteins, and DNA. The animal immune system (cell mediated immune response) uses oxygen molecules to kill foreign organisms. B. abortus causes a cattle disease called brucellosis. The mechanism for bacteria to survive and adapt in the face of oxidative attack is thought to be important for understanding pathogenesis. This dissertation presents the response of B. abortus to oxidative stress and the regulation of catalase as a defensive mechanism;Different protein expression patterns were observed during oxidative stress by conducting 2-D protein gel analysis ...


Genetic Construction And Biochemical Analysis Of Thermostability Mutants Of Glucoamylase From Aspergillus Awamori , Yuxing Li Jan 1996

Genetic Construction And Biochemical Analysis Of Thermostability Mutants Of Glucoamylase From Aspergillus Awamori , Yuxing Li

Retrospective Theses and Dissertations

To study the molecular basis of Aspergillus awamori glucoamylase (GA) thermostability, eighteen mutants were constructed by site-directed mutagenesis and expressed in Saccharomyces cerevisiae based on thermostability theories. Four lysine residues, K61, K279, K352 and K404, were replaced with arginine, with all but K404 well exposed to the solvent and far away from the enzyme activity site. Mutations K61F/D65E and H254W/E326Q were made to fill a packing void around the inner set of six [alpha]-helices of GA and to displace water molecules inside the void. Five residues (A27, A393, A435, Ser436 and Ser460) were replaced with proline. Two ...


Integration Specificity Of The Retrovirus-Like Transposable Element Ty5 Of Saccharomyces , Sige Zou Jan 1996

Integration Specificity Of The Retrovirus-Like Transposable Element Ty5 Of Saccharomyces , Sige Zou

Retrospective Theses and Dissertations

The retrotransposons and retroviruses display a strong preference in selecting integration sites. The molecular mechanisms underlying this process, however, are largely unknown. I have characterized a new retrotransposon, called Ty5, in diverse strains of Saccharomyces cerevisiae and related species. A functional element, Ty5-6p, was identified from S. paradoxus. To investigate Ty5 target preference, the locations of 13 native insertions were determined in S. cerevisiae and S. paradoxus. Twelve were found near the telomeres and the mating locus HMR. To determine if this distribution is a consequence of targeted integration, a Ty5 transposition assay was developed in S. cerevisiae using Ty5-6p ...


Purification, Characterization And Cloning Of A Periplasmic Catalase From B Abortus And The Role It Plays In The Pathogenesis Of Brucella , Zheng Yu Sha Jan 1994

Purification, Characterization And Cloning Of A Periplasmic Catalase From B Abortus And The Role It Plays In The Pathogenesis Of Brucella , Zheng Yu Sha

Retrospective Theses and Dissertations

A periplasmic catalase has been identified and purified from Brucella abortus using a procedure which fractionates periplasmic B. abortus proteins from other cellular components while retaining biological activity. The biochemical characteristics of the purified enzyme were studied and the gene encoding the enzyme cloned and sequenced. SDS polyacrylamide gel electrophoresis of the purified enzyme revealed only a single subunit with a molecular weight of 59,000. Gel filtration indicates the native protein is a tetramer. The native protein has a visible absorption spectrum with maxima at 407, 501, and 628 nm which is typical of mammalian, but not some bacterial ...


Characterization And Immunogenicity Of The Heat Shock Protein, Hsp60 Of Brucella Abortus , Dennis Gor Jan 1994

Characterization And Immunogenicity Of The Heat Shock Protein, Hsp60 Of Brucella Abortus , Dennis Gor

Retrospective Theses and Dissertations

Brucella abortus is the causative agent of bovine brucellosis, a disease that causes spontaneous abortion in cows. The most effective form of protection against this pathogen is immunization; however, Brucella abortus strain 19 (the standard vaccine against Brucella abortus) is not completely protective. The vaccination of laboratory mice with the heat shock protein, hsp60 derived from Brucella abortus, using live attenuated recombinant Salmonella typhimurium expressing this protein (hsp60) as a delivery system, and the characterization of the immune response to Brucella abortus hsp60 over a 12 week time course following vaccination is described;Infection of BALB/c strain of laboratory ...


Cloning, Sequencing, And Expression Of Brucella Abortus Heat Shock 70 Gene , Emily C. L. Chin Jan 1993

Cloning, Sequencing, And Expression Of Brucella Abortus Heat Shock 70 Gene , Emily C. L. Chin

Retrospective Theses and Dissertations

Brucella abortus is a gram negative bacteria that can infect and cause serious disease in many mammals including humans. Any organism, including Brucella, that can survive as an intracellular parasite must be able to survive the stress of a foreign and often hostile environment of the host. Stress usually results in a dramatic change in gene expression including an elevated synthesis of heat shock proteins;We have subcloned, sequenced and expressed the Brucella HSP70 and the upstream sequences. The gene was put under the control of the strong "tac" promoter. However, when expressed, we saw a high accumulation of a ...


Safety And Potency Testing Of Veterinary Vaccines , Louise Mary Henderson Jan 1993

Safety And Potency Testing Of Veterinary Vaccines , Louise Mary Henderson

Retrospective Theses and Dissertations

Prior to licensing of veterinary vaccines, it is essential to demonstrate that the use of the product is safe (e.g., use of the product will not have unexpected or undesirable effects on animals exposed to the agent or on the environment) and potent (e.g., produces the desired result). The projects described in this dissertation demonstrate research directed toward the development and improvement of safety and potency testing of veterinary vaccines from a regulatory perspective;In the first study, recombination between vaccine strains of pseudorabies virus (PRV) resulting in the creation of strains with undesirable virulence and antigenic combinations ...


Analysis Of Three Plasmids From Filamentous, Nitrogen-Fixing Cyanobacteria , Douglas Kevin Walton Jan 1991

Analysis Of Three Plasmids From Filamentous, Nitrogen-Fixing Cyanobacteria , Douglas Kevin Walton

Retrospective Theses and Dissertations

The cyanobacteria are an ancient and diverse group of prokaryotes capable of oxygenic photosynthesis. They display both unicellular and filamentous cell types and some have the ability to fix atmospheric dinitrogen, and the ability to differentiate specialized cells. In addition, many of the cyanobacteria possess plasmids. To date, only one plasmid, from a unicellular non-nitrogen-fixer, has been characterized in detail. The current lack of information concerning cyanobacterial plasmids, and their subsequent use as vectors, has hindered genetic analysis, particularly in the filamentous species;In this study, the properties of two plasmids and one plasmid origin of replication from filamentous, nitrogen-fixing ...