Microbiology Commons^™

The Role Of Viruses In Fe Recycling In The World's Oceans, Leo Poorvin

Doctoral Dissertations

Viral lysis is responsible for a significant fraction of bacterioplankton mortality in marine systems. This work shows that viral lysis of both heterotrophic bacterial and autotrophic cyanobacterial plankton releases iron (Fe) at a greater rate than is released from unlysed cells. These studies also show that the Fe released is bound to organic ligands, these ligands are not siderophores, and that these ligands have Fe binding stability constants similar to organic ligands found in seawater. Further, these studies have shown Fe released via viral lysis to be highly bioavailable to a range of model marine plankton and may potentially satisfy …

Understanding Immune Response In Mycobacterium Ulcerans Infection, Sarojini Adusumilli

Doctoral Dissertations

Buruli ulcer is a necrotizing skin infection and is the third most important mycobacterial disease in immune competent individuals after tuberculosis and leprosy in humid tropical countries. The causative agent Mycobacterium ulcerans is unlike other mycobacterial pathogens in that it appears to maintain an extracellular location during infection. Another unusual feature of the bacterium is that it is the only mycobacterium known to produce a dermo-necrotic polyketide toxin called mycolactone. A single Buruli ulcer, which can cover 15% of a person's skin surface, contains huge numbers of extracellular bacteria. The infection is characterized by massive necrosis at the site of …

Studies On The Role Of Specific Residues Of The Saccharomyces Α-Factor Pheromone Receptor (Ste2p) In The Inactive And Active State, Yong-Hun Lee

Doctoral Dissertations

G protein-coupled receptors (GPCRs) are a class of integral membrane receptor proteins that are characterized by seven-transmembrane (7TM) domains connected by intracellular and extracellular loops, an extracellular N-terminus, and an intracellular C-terminus. To date more than 1000 GPCRs have been identified, and these proteins recognize neurotransmitters, sensory molecules and chemotactic agents. These receptors are involved in the control of many aspects of metabolism and play important roles in diverse processes such as pain perception, growth and blood pressure regulation, and viral pathogenesis. Therefore, these proteins became important target for therapeutic agents and recent reports indicate that nearly 40% of drugs …

The Bovine Coronavirus 2'-O-Methyltransferase Binds Cis-Acting Stem-Loop Iv In The 5-Prime Untranslated Region Of The Viral Genome, Tara Beth Tucker

Masters Theses

The positive-stranded coronavirus genome, at 32 kilobases in length, is the largest known viral RNA genome, and internal cis-signaling elements directing its replication have been described only within the last ten years. The bovine coronavirus genome encodes 26 proteins in the region between the 5’-terminal 210-nt untranslated region and the 3’-terminal 298-nt untranslated region. Here, genes for 5 of the 26 proteins were cloned into bacterial expression plasmids for the long-term goals of characterizing enzymatic and RNA binding properties. These genes encode enzymes postulated to interact directly with the cis-acting RNA elements and carry out RNA synthesis, namely, the …

Cloning And Expression Of A Putative P450 From Mycobacterium Ulcerans, Yang Wang

Masters Theses

Mycolactones are macrocyclic polyketide toxins produced by the pathogen Mycobacterium ulcerans, the etiologic agent of the emerging human disease known as Buruli ulcer. A giant virulence plasmid in Mycobacterium ulcerans encoding giant polyketide synthases is responsible for the synthesis of the lipid toxin mycolactone. Mycobacterium ulcerans from different geographic origins produce varieties of mycolactones including mycolactone A/B, C E. Their difference is observed by thin layer chromagraph, mass spectrometry, cytopathic assays. The presence of different mycolactone correlates with plasmid variation. Australian strains lacking the hydroxyl group at C-12’ produce a mycolactone with a mass of [M + Na]+ at …

In Situ Biostimulation Of Uranium Reducing Microorganisms At The Old Rifle Umtra Site, Yun-Juan Chang

Doctoral Dissertations

Bioremediation is a promising strategy for cleaning up heavy metal and radionuclide contamination. Nutrient or electron donor amendment is an increasingly accepted practice used to stimulate the growth of microorganisms capable of immobilizing dissolved uranium in situ, but there is scant understanding of the systematic effects of nutrient addition on indigenous microbial populations or the progress of the bioremediation. Successful implementation of metal and radionuclide bioremediation in heterogeneous environments requires an understanding of the complex microbial and geochemical interactions that influence the redox speciation and mobility of toxic metals.

The major challenge in microbial ecology and biogeochemistry is to …

Virus Dynamics In High-Nutrient, Low-Chlorophyll Marine Surface Waters, Julie Linda Higgins

Masters Theses

Iron (Fe) limitation of primary productivity in high-nutrient, low-chlorophyll (HNLC) regions is relatively well-studied. Iron fertilization experiments as well as bottle incubations have been used to study changes in phytoplankton community biomass and diversity, changes in bacterial growth rates, etc. However, viral activity has been largely ignored in these studies. Viral activity was monitored during an iron budget study (FeCycle) in the HNLC waters of the Southern Ocean southwest of New Zealand as well as during a mesoscacle iron fertilization in the subarctic Pacific (SEEDS II). The goal of these studies was to evaluate the role of viruses in the …

Methanogen Diversity Evidenced By Molecular Characterization Of Methyl Coenzyme M Reductase A (Mcra) Genes In Hydrothermal Sediments Of The Guaymas Basin, Ashita Dhillon, Mark Lever, Karen Lloyd, Daniel B. Albert, Mitchell L. Sogin, Andreas Teske

Microbiology Publications and Other Works

The methanogenic community in hydrothermally active sediments of Guaymas Basin (Gulf of California, Mexico) was analyzed by PCR amplification, cloning, and sequencing of methyl coenzyme M reductase (mcrA) and 16S rRNA genes. Members of the Methanomicrobiales and Methanosarcinales dominated the mcrA and 16S rRNA clone libraries from the upper 15 cm of the sediments. Within the H2/CO2- and formate-utilizing family Methanomicrobiales, two mcrA and 16S rRNA lineages were closely affiliated with cultured species of the genera Methanoculleus and Methanocorpusculum. The most frequently recovered mcrA PCR amplicons within the Methanomicrobiales did not branch with any cultured genera. Within the nutritionally versatile …

Effects Of Dissolved Sulfide, Ph, And Temperature On Growth And Survival Of Marine Hyperthermophilic Archaea, Karen Lloyd, Virginia P. Edgcomb, Stephen J. Molyneaux, Simone Böer, Carl O. Wirsen, Michael S. Atkins, Andreas Teske

Microbiology Publications and Other Works

The ability of metabolically diverse hyperthermophilic archaea to withstand high temperatures, low pHs, high sulfide concentrations, and the absence of carbon and energy sources was investigated. Close relatives of our study organisms, Methanocaldococcus jannaschii, Archaeoglobus profundus, Thermococcus fumicolans, and Pyrococcus sp. strain GB-D, are commonly found in hydrothermal vent chimney walls and hot sediments and possibly deeper in the subsurface, where highly dynamic hydrothermal flow patterns and steep chemical and temperature gradients provide an ever-changing mosaic of microhabitats. These organisms (with the possible exception of Pyrococcus strain GB-D) tolerated greater extremes of low pH, high sulfide concentration, and high temperature …

Lack Of Antigen-Specific Tissue Remodeling In Mice Deficient In The Macrophage Galactose-Type Calcium-Type Lectin 1/Cd301a., Thandi M. Onami, K. Sato, Y. Imai, N. Higashi, Y. Kumamoto, S. M. Hedrick, T. Irimura

Microbiology Publications and Other Works

Macrophage galactose-type C-type lectins (MGLs), which were recently named CD301, have 2 homologues in mice: MGL1 and MGL2. MGLs are expressed on macrophages and immature dendritic cells. The persistent presence of granulation tissue induced by a protein antigen was observed in wild-type mice but not in mice lacking an endogenous, macrophage-specific, galactose-type calcium-type lectin 1 (MGL1) in an air pouch model. The anti-MGL1 antibody suppressed the granulation tissue formation in wild-type mice. A large number of cells, present only in the pouch of MGL1-deficient mice, were not myeloid or lymphoid lineage cells and the number significantly declined after administration of …