Bacteriology Commons^™

Mechanisms Of Antimicrobial Peptide Resistance In Campylobacter, Ky Van Hoang

Doctoral Dissertations

Campylobacter is the major bacterial cause of human gastroenteritis in the United States and other developed countries. Poultry are considered a main source of human Campylobacter infections. Thus, reduction of Campylobacter load in poultry is significant in food safety and public health. However, no effective measure is commercially available to prevent Campylobacter colonization in poultry to date. Antimicrobial peptides (AMPs) are short and bactericidal peptides widely present in intestine to limit bacterial infections. Recently, AMPs have been increasingly recognized as a novel class of antibiotics (peptide antibiotics) to control foodborne pathogens. Notably, several potent anti-Campylobacter bacteriocins, a group of AMPs …

Deletion Of The Cel48s Cellulase From Clostridium Thermocellum, Daniel G. Olson, Shital A. Tripathi, Richard J. Giannone, Jonathan Lo, Nicky C. Caiazza, David A. Hogsett, Robert L. Hettich, Adam M. Guss, Genia Dubrovsky, Lee R. Lynd

Dartmouth Scholarship

Clostridium thermocellum is a thermophilic anaerobic bacterium that rapidly solubilizes cellulose with the aid of a multienzyme cellulosome complex. Creation of knockout mutants for Cel48S (also known as CelS, S(S), and S8), the most abundant cellulosome subunit, was undertaken to gain insight into its role in enzymatic and microbial cellulose solubilization. Cultures of the Cel48S deletion mutant (S mutant) were able to completely solubilize 10 g/L crystalline cellulose. The cellulose hydrolysis rate of the S mutant strain was 60% lower than the parent strain, with the S mutant strain also exhibiting a 40% reduction in cell yield. The cellulosome produced …

Growth Of Lactic Acid Bacteria: Infuence Of Protocooperation, Bacteriophage Infection, And Prebiotic Carbohydrates, Caitlin D. Goin

Dissertations and Theses in Biological Sciences

Lactic acid bacteria are a vital part of the fermented food industry and are the subject of much interest and research. Industry is especially interested in using modern molecular approaches to maintain and improve selected strains; several industrial uses could be improved by closer investigation, namely the protocooperation of S. thermophilus and L. bulgaricus, the role of CRISPRs in phage resistance, and the utilization of prebiotic carbohydrates. Questions such as what genes and pathways are shared during milk fermentation between S. thermophilus and L. bulgaricus, when and what genes are active during bacteriophage infection, and how and where …

Isolation Of A Siderophore Produced By Methicillin-Resistant Staphylococcus Aureus Strain H372., Rachel Elizabeth Presswood

Electronic Theses and Dissertations

Iron is necessary for many cellular processes such as the electron transport chain and gene regulation. However, most iron on earth is found in insoluble iron-hydroxide complexes. In addition, iron is tightly sequestered in the human body by proteins such as transferrin, making it unavailable for pathogens. In order to overcome these limitations bacteria have evolved siderophores. Siderophores are low molecular weight compounds that bind ferric iron with a high affinity. Staphylococcus aureus is an important human pathogen that is known to produce at least four siderophores, and these siderophores contribute to its virulence. S. aureus strain H372 was found …

Examination Of Germination Receptors Of B. Subtilis And B. Megaterium, Shruti Patel, Alessio Luinetti, Ernesto Abel-Santos, Eduardo Robleto

Undergraduate Research Opportunities Program (UROP)

Many bacterial species including those in the Bacilli group form spores as a mechanism to survive harsh conditions such as extreme temperature, radiation, chemicals, and nutrient starvation. By forming spores, they can remain metabolically dormant for an extended period and revert to their vegetative form when environment becomes favorable. This resumption of metabolism and growth is marked by a process called germination that is triggered by exogenous nutrients such as amino acids, sugars, and nucleotides. The (Ger) germination receptors that are postulated to respond to these germinants, in the case of B. subtilis and B. megaterium, are a complex of …

The Small Regulatory Rna Ryhb Regulates Icsa Expression In Shigella Flexneri, Nick Egan, Helen J. Wing

Undergraduate Research Opportunities Program (UROP)

Shigella flexneri is a gram negative non-motile, non-spore forming, rod-shaped bacterium responsible for bacillary dysentery in humans. The master regulator, VirF, initiates a cascade of virulence gene activation by acting as a transcription factor for the gene encoding the global regulator, VirB (1). Production of VirB is also negatively regulated by the regulatory small RNA (sRNA), RyhB 2). Regulatory sRNAs are untranslated RNA molecules involved in the regulation of both transcription and translation. RyhB, a 90 nt sRNA, was first identified in E. coli and subsequently found in all Shigella species. In Shigella this sRNA is maximally expressed in response …

Antibiotic Resistance In Bacillus Subtilis As Affected By Transcriptional Derepression And The Stringent Response, Brandon Eisinger, Ronald E. Yasbin, Eduardo A. Robleto

Undergraduate Research Opportunities Program (UROP)

Bacterial cells under conditions of starvation or prolonged non-lethal selective pressures accumulate mutations in highly transcribed genes. This process is part of cellular programs to increase genetic diversity in conditions of stress, also known as stationary phase or stress-induced mutagenesis. This experiment investigated mutation frequencies for antibiotic resistance as affected by the stringent response. The stringent response is a global cellular process that initiates at the cessation of growth and mediates changes in gene expression that repress synthesis of ribosome components. We used Bacillus subtilis strains that differ in RelA proficiency. The relA gene controls the synthesis of (p)ppGpp, the …

Evaluation Of Virb Binding Site Contribution To The Regulation Of The Icsp Promoter In Shigella Flexneri, Juan C. Duhart, Maria I. Castellanos, Helen J. Wing

Undergraduate Research Opportunities Program (UROP)

Shigella species are gram-negative, rod-shaped bacteria that are closely related to Escherichia coli. Virulent Shigella spp. are intracellular pathogens that invade, replicate and spread through epithelial cells of the lower intestine and cause bacillary dysentery in humans. This disease is characterized by a robust inflammatory response that results in fever, abdominal pain, and bloody diarrhea (3). According to the CDC, approximately 14,000 cases are reported each year in the United States alone. This number however, does not reflect the actual incidence of this disease as many cases go unreported. The molecular pathogenesis of these bacteria lies in the large virulence …

Transcriptional Regulation Of The Shigella Flexneri Icsp Promoter: Silencing And Anti-Silencing By H-Ns And Virb, Dustin Harrison

UNLV Theses, Dissertations, Professional Papers, and Capstones

Shigella species are gram-negative intracellular pathogens that cause bacillary dysentery in humans. Many genes required for virulence of Shigella are carried on a large 230 kb plasmid and many of these are under the transcriptional control of the histone-like nucleoid structuring protein (H-NS) and by the major virulence regulator VirB. At the non-permissive temperature of 30⁰C, H-NS represses transcription, while at 37⁰C VirB alleviates this repression. This mechanism of gene regulation has been coined "silencing/anti-silencing" and is commonly found in many important bacterial pathogens including Salmonella spp. and Yersinia spp. The icsP gene, encoded by the Shigella virulence plasmid, is …

Probiotic Therapy - Recruiting Old Friends To Fight New Foes, Roy D. Sleator

Department of Biological Sciences Publications

Against a backdrop of increasing antibiotic resistance, and the emergence of new and evolving pathogens, clinicians are increasingly forced to consider alternative therapies - probiotics are one such alternative.

Constraint-Based Model Of Shewanella Oneidensis Mr-1 Metabolism: A Tool For Data Analysis And Hypothesis Generation, Grigoriy E. Pinchuk, Eric A. Hill, Oleg V. Geydebrekht, Jessica De Ingeniis, Xiaolin Zhang, Andrei Osterman, James H. Scott

Dartmouth Scholarship

Shewanellae are gram-negative facultatively anaerobic metal-reducing bacteria commonly found in chemically (i.e., redox) stratified environments. Occupying such niches requires the ability to rapidly acclimate to changes in electron donor/acceptor type and availability; hence, the ability to compete and thrive in such environments must ultimately be reflected in the organization and utilization of electron transfer networks, as well as central and peripheral carbon metabolism. To understand how Shewanella oneidensis MR-1 utilizes its resources, the metabolic network was reconstructed. The resulting network consists of 774 reactions, 783 genes, and 634 unique metabolites and contains biosynthesis pathways for all cell constituents. Using constraint-based …

Isolation And Identification Of The Siderophore "Vicibactin" Produced By Rhizobium Leguminosarum Atcc 14479., William H. Wright Iv

Electronic Theses and Dissertations

Siderophores are small, iron chelating molecules produced by many bacteria to help meet the iron requirements of the cell. Multiple metabolic functions require iron as it serves as a cofactor in many enzymes and cellular processes. However, in the presence of oxygen and at physiologic pH, iron forms insoluble ferric complexes that cause the nutrient to be unavailable to bacterial cells. Siderophores alleviate this limitation by chelating the ferric iron, rendering it soluble and available for uptake. One group of microorganisms known for their ability to produce siderophores is the rhizobia. These bacteria are characterized both by their formation of …

Inhibition Of Escherichia Coli Atp Synthase By Polyphenols And Their Derivatives., Prasanna Keerthi Dadi

Electronic Theses and Dissertations

We have studied the inhibitory effect of natural and structurally modified polyphenols on Escherichia coli ATP synthase to test (I) if the beneficial dietary effects of polyphenols are related to their inhibitory actions on ATP synthase, (II) if inhibitory effects of polyphenolic compound could be augmented through structural modifications, and (III) if they can act as antimicrobial agent through their actions on ATP synthesis. X-ray crystal structures of polyphenol binding sites suggested that polyphenols bind at a distinct polyphenol binding pocket, at the interface of α,β,γ-subunits. We found that both natural and modified polyphenols inhibit E. coli ATP synthase to …

Natural Competence In Thermoanaerobacter And Thermoanaerobacterium Species, A Joe Shaw, David A. Hogsett, Lee R. Lynd

Dartmouth Scholarship

Low-G+C thermophilic obligate anaerobes in the class Clostridia are considered among the bacteria most resistant to genetic engineering due to the difficulty of introducing foreign DNA, thus limiting the ability to study and exploit their native hydrolytic and fermentative capabilities. Here, we report evidence of natural genetic competence in 13 Thermoanaerobacter and Thermoanaerobacterium strains previously believed to be difficult to transform or genetically recalcitrant.

In Thermoanaerobacterium saccharolyticum JW/SL-YS485, natural competence- mediated DNA incorporation occurs during the exponential growth phase with both replicating plasmid and homologous recombination-based integration, and circular or linear DNA. In T. saccharolyticum, disruptions of genes similar to …

Bacillus Cereus And Bacillus Anthracis Germination Kinetics: A Michaelis-Menten Approach, Helen Luu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Bacillus species are rod-shaped, gram-positive bacteria that are capable of producing endospores. In this dormant stage, the endospores can persist in hostile physical and chemical environments. Once conditions become favorable, the spores germinate into actively dividing cells, vegetative cells. Germination is a crucial step for the pathogenicity of the Bacilli in affecting a host organism.

Our study applies mathematical approaches to spore germination to determine whether the binding of one germinant will affect the binding of another germinant. We pursued this approach with two different species, B. cereus and B. anthracis, both pathogenic organisms. B. cereus is a widely known …

Role Of Flgt In Anchoring The Flagellum Of Vibrio Cholerae, Raquel M. Martinez, Brooke A. Jude, Thomas J. Kirn, Karen Skorupski, Ronald K. Taylor

Dartmouth Scholarship

Flagellar motility has long been regarded as an important virulence factor. In Vibrio cholerae, the single polar flagellum is essential for motility as well as for proper attachment and colonization. In this study, we demonstrate that the novel flagellar protein FlgT is involved in anchoring the flagellum to the V. cholerae cell. A screen for novel colonization factors by use of TnphoA mutagenesis identified flgT. An in-frame deletion of flgT established that FlgT is required for attachment, colonization, and motility. Transmission electron microscopy revealed that while the flgT mutant is capable of assembling a phenotypically normal flagellum, …

Dual-Action Hygienic Coatings: Benefits Of Hydrophobicity And Silver Ion Release And Surface Analysis, Niall Stobie, Brendan Duffy, John Colreavy, Patrick Mchale, Steven Hinder, Declan Mccormack

Articles

Coatings that demonstrate reduced attachment of crystalline precipitates and the medical device colonising Staphylococcus epidermidis were prepared by the immobilisation of silver doped perfluoropolyether–urethane siloxane thin films on glass substrates. The presence of stratified hydrophobic perfluoropolyether groups protects the coating surface from the attachment of crystalline hydrophilic species such as chlorides and phosphates, whilst silver ion release inhibited attachment of S. epidermidis and subsequent biofilm formation in vitro. The release of silver ions protects the perfluoro groups from the hydrophobic interactions of S. epidermidis cells, which can reduce the hydrophobicity of the protective coating. These coatings also exhibited significant antibacterial …

Crystal Structure Of The Cystic Fibrosis Transmembrane Conductance Regulator Inhibitory Factor Cif Reveals Novel Active-Site Features Of An Epoxide Hydrolase Virulence Factor, Christopher D. Bahl, Christophe Morisseau, Jennifer M. Bomberger, Bruce A. Stanton, Bruce D. Hammock, George A. O'Toole, Dean R. Madden

Dartmouth Scholarship

Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other alpha/beta hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-A resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across the …

Diversity Of Oligotrichia And Choreotrichia Ciliates In Coastal Marine Sediments And In Overlying Plankton, Jan A.C. Vriezen Dr., Mary Doherty Dr., Maiko Tamura Dr., George B. Mcmanus Dr.

Jan A.C. Vriezen Dr.

Elucidating the relationship between ciliate communities in the benthos and the plankton is critical to understanding ciliate diversity in marine systems. Although data for many lineages are sparse, at least some members of the dominant marine ciliate clades Oligotrichia and Choreotrichia can be found in both plankton and benthos, in the latter either as cysts or active forms. In this study, we developed a molecular approach to address the relationship between the diversity of ciliates in the plankton and those of the underlying benthos in the same locations. Samples from plankton and sediments were compared across three sites along the …

Regulation Of Polar Peptidoglycan Biosynthesis By Wag31 Phosphorylation In Mycobacteria, Charul Jani, Hyungjin Eoh, Jae Lee, Khozima Hamasha, Moodakare Sahana, Jeong-Sun Han, Seeta Nyayapathy, Jung-Yeon Lee, Joo-Won Suh, Sang Lee, Steve J. Rehse, Dean C. Crick, Choong-Min Kang

Wayne State University Associated BioMed Central Scholarship

Abstract

Background

Sensing and responding to environmental changes is a central aspect of cell division regulation. Mycobacterium tuberculosis contains eleven Ser/Thr kinases, two of which, PknA and PknB, are key signaling molecules that regulate cell division/morphology. One substrate of these kinases is Wag31, and we previously showed that partial depletion of Wag31 caused morphological changes indicative of cell wall defects, and that the phosphorylation state of Wag31 affected cell growth in mycobacteria. In the present study, we further characterized the role of the Wag31 phosphorylation in polar peptidoglycan biosynthesis.

Results

We demonstrate that the differential growth among cells expressing different …