Bacteriology Commons^™

Exploring Competitive Dynamics Between Pseudomonas Baetica And Salmonella In A Polymicrobial System, Braxton E.M. Stout

Electronic Theses and Dissertations

The global rise in antimicrobial resistance has catalyzed a greater focus on polymicrobial research aimed at characterizing microbial interactions and uncovering new therapeutic strategies. Though it has long been of interest, environmental soil-derived bacteria remain largely under-represented in research and thus uncharacterized in this field. This project aimed to identify soil microbes that display inhibitory mechanisms to potential nosocomial pathogens. Soil sample S1S3-2 displayed inhibitory phenotypes toward numerous bacteria and was identified as Pseudomonas baetica. In both planktonic and biofilm growth, P. baetica was able to inhibit Salmonella arizonae through a contact-dependent and temperature-dependent manner. Screening of a transposon insertion …

Strategic Enhancement Of Biofuel Production Using Bacillus Subtilis As A Model Organism: A Dual Approach Of Gene Essentiality Mapping And Optimization, Angela A. Zebede

Electronic Theses and Dissertations

With rising global demand for renewable energy, enhancing microbial platforms for biofuel production is vital. This study engineered Bacillus subtilis to improve resilience to solvent stress by targeting membrane lipid biosynthesis pathways essential for integrity. Growth curve analysis (OD₆₀₀) showed that phosphatidylserine (PS) and phosphatidylethanolamine (PE) knockout strains grew significantly slower than wild type (168), indicating the importance of these lipids under stress. Laurdan fluorescence spectroscopy was used to assess membrane properties. Generalized polarization (GP) analysis revealed a concentration-dependent reduction in membrane order upon 1%–2% 1-butanol exposure. GP values declined progressively from control to 2% treatment, reflecting increased membrane fluidity …

Isolation And Characterization Of Rhizobia Bacteria From Midwest Soils, Jr Loya

Electronic Theses and Dissertations

Symbiotic bacteria, known as rhizobia, can colonize the roots of legume plants and then convert atmospheric nitrogen into a usable form by the host through the process called biological nitrogen fixation (BNF). Many of these bacteria produce other plant-growth-promoting benefits, such as nutrient acquisition, phytohormone production, and the modification of plant stress responses. Agricultural inoculants made from these bacteria have helped reduce the need for man-made nitrogenous fertilizers, known causes of pollution and eutrophication. There are additional benefits in developing bacteria inoculants local to regional soils. The ability to survive and compete in Midwest soil and climates present an opportunity …

Analysis Of Microbiome In Various Human Medical Conditions Using Next-Generation Sequencing Of The 16s Rrna Gene, Pallavi Sharma

Electronic Theses and Dissertations

Studies of human microbiomics, spanning diverse anatomical sites, offer a unique perspective into the complex microbial communities within the body. Influenced by age, gender, and disease, it mirrors broader microbial ecosystems. This study specifically delves into the ocular and gastrointestinal tract microbiome, comparing its composition in 43 healthy and diseased patients using 16S rRNA gene sequencing. We identified a rich microbial landscape, identifying over 338 bacterial taxa. Notably, Acinetobacter, Cutibacterium, Acidovorax and Herbaspirillum were prevalent in the ocular samples and Akkermansia, Faecalibacterium, and Anaerostipes were mostly prevalent in gut samples. Moreover, dry eye disease conditions were characterized by …

Pilz Domain-Containing Proteins Regulate Motility In Acinetobacter Baumannii, Gabriel Smith

Electronic Theses and Dissertations

Acinetobacter baumannii is an increasingly multidrug-resistant pathogen contributing to hospital-acquired infections, necessitating a greater understanding of how it interacts with its surroundings. Many bacteria utilize different methods of bacterial motility to move about and interact with these surroundings. A bacterial second messenger, cyclic diguanosine monophosphate (c-di-GMP), can regulate various motility factors that are potentially advantageous for survival in and adaptation to their environment. Concentrations of c-di-GMP are regulated by specific synthesizing and degrading enzymes. Controlled levels of c-di-GMP allow interaction between the c-di-GMP and its binding effectors that induce changes in bacterial phenotypes such as biofilm formation and motility. A …

Breaking Virulent: The Coincidental Evolution Of Virulence Factors In Bacteria., Rhiannon Emmanuelle Cecil

Electronic Theses and Dissertations

Understanding how innocuous organisms can evolve to be pathogenic to humans is of increasing global concern. Further, understanding how existing pathogens may evolved to be more virulent is also vital to our ability to provide healthcare to people afflicted with diseases that promote chronic bacterial infections, such as cystic fibrosis. With the rise of antibiotic resistance in both bacteria and fungi it is paramount that new therapeutics are identified. Understanding what mutations occur that result in increased virulence in microbes can potentially provide new targets for antimicrobial drugs to combat antibiotic resistance. The Coincidental Evolution Hypothesis is a fundamental hypothesis …

Analyzing Pseudomonas Aeruginosa With Bacteriophage Tags Using Photoacoustic Flow Cytometry, Jennifer C. Schinke

Electronic Theses and Dissertations

The number of daily bacterial infections is climbing and the CDC explains that this is due to the antibiotic-resistant threat in the United States. Finding a faster way of bacterial identification is necessary as it currently takes 1-4 days for a medical lab to culture and identify bacteria. Photoacoustic flow cytometry (PAFC) can be used as an alternative method resulting in swift identification within an hour (Edgar, 2019). Pseudomonas aeruginosa, cell line PA01, will be coated in up to a few hundred red dyed phages making it detectible by the photoacoustic flow cytometry system. Bacteriophages (phages) are viruses that …

Spatial Structure Formation By The Post-Transcriptional Gene Regulator Rsme In Pseudomonas Fluorescens Pf0-1, Anton Evans

Electronic Theses and Dissertations

Microorganisms are often found in microbial communities we call biofilms. Organisms living in these crowded environments have significant evolutionary pressure to retain access to the resources necessary to sustain life. My research uses the bacterium Pseudomonas fluorescens Pf0-1 to study how organisms evolve strategies to solve this crowding problem as aging colonies repeatedly generate mutant patches. These mutants expand the reach of the colony resulting in decreased local density as they push themselves up to the resource rich surface. These spatial structures result from social interactions between the mutant and the parental cells mediated through extracellular secretions, resulting in the …

Use Of Transposon Screening For Salicylic Acid-Assisted Desiccation Killing In Salmonella, Shannon D. Elliott

Electronic Theses and Dissertations

Salmonella enterica serovar Typhimurium is one of the most prevalent food-borne pathogens, affecting millions around the world every year, making it a threat to global health. Salmonella possesses the ability to survive the normally lethal condition of desiccation, however, discovery of the genes and mechanisms behind this phenomenon are still ongoing. Using a transposon mutagenesis approach to construct a broad transposon library, this study aimed to uncover genes that may be contributing to changes in Salmonella’s survivability under desiccation, particularly when exposed to the antimicrobial molecule salicylic acid. Building on previous findings showing salicylic acid can alter cell viability …

The Stringent Response In Pseudomonas Aeruginosa Influences The Phenotypes Controlled By The Gac/Rsm System, Michael Shawn Hooker

Electronic Theses and Dissertations

Pseudomonas aeruginosa is a ubiquitous, opportunistic pathogen that causes acute and chronic infections. Infection is typically initiated via motile and virulent strains. After exposure to stressors, acute infections make both genotypic and phenotypic switches to a chronic, sessile strain. This is due to intricate regulatory networks directing gene expression in response to stressors. One network, GacA/GacS, has been established to control virulence factors. The stringent response of bacteria is mediated by alarmones produced primarily by RelA which responds to starvation.

To study the effect of the stringent response on the virulence switch. A series of experiments were run in both …

Inhibiting Survival Of Salmonella During Desiccation Through The Use Of Naturally Occurring Signals, Joseph Headrick

Electronic Theses and Dissertations

A rising problem in agriculture is the increase of antibiotic-resistant Salmonella cases associated with chicken eggs, which transmit infection to humans. To counter this, new approaches to combat Salmonella in chickens and desiccated on eggshells are vital in the prevention of human foodborne illness. Disrupting signaling pathways with naturally occurring compounds provides a potential novel avenue for prevention of Salmonella infections, as this would disrupt sensing of these environments and inhibit subsequent optimal gene expression. Starting with signals identified in previous studies, salicylic acid was found to inhibit Salmonella desiccation survival on both eggshells and plastic. To expand upon this, …

Indigenous Toxin Affects Cell Viability, While An Artificial Proteolytic Queueing Causes The Upregulation Of Specific Genes, Mohammed Salahuddin

Electronic Theses and Dissertations

Studying bacterial physiology is crucial to understand the fundamental mechanisms that govern bacterial growth, survival, and adaptation. This thesis combines two chapters investigating bacterial physiology by studying important cellular processes like bacterial toxin-antitoxin systems and proteolytic pathways. The first chapter involves studying bacterial toxin-antitoxin systems to understand the regulation and function of hypothetical toxin-antitoxin (TA) systems of bacteria and the effects of these TA systems on bacterial growth and survival. The emergence of these genetic modules in bacterial research and the unrevealing of some of their important roles in cell physiology in recent years has drawn much attention in scientific …

Novel Signal Sequences And Fusion Partners For Paratransgenesis In Asaia, Christina Grogan

Electronic Theses and Dissertations

Mosquitoes transmit many pathogens that cause human disease. One such disease, malaria, is caused by parasites in the genus Plasmodium, infecting over 200 million people and killing over 600,000 per year. Current strategies to control vector-transmitted diseases are increasingly undermined by mosquito and pathogen resistance. Research has turned to additional and novel methods of control, such as altering the microbiota of the vectors. In this method, called paratransgenesis, symbiotic bacteria are genetically modified to affect the mosquito’s phenotype by engineering them to deliver antiplasmodial molecules into the midgut to kill parasites. These molecules must be released by the …

Cyclic Di-Gmp Regulates Motility, Biofilm Formation, And Desiccation Tolerance In Acinetobacter Baumannii, Garrett Reynolds

Electronic Theses and Dissertations

Acinetobacter baumannii is an increasingly multidrug-resistant pathogen contributing to hospital-acquired infections necessitating the discovery of novel treatments. A bacterial second messenger, cyclic diguanosine monophosphate (cyclic di-GMP), can regulate various persistence factors that are potentially advantageous for survival in hospital environments. Cyclic di-GMP–modulating enzymes and cyclic di-GMP–binding effectors predictively are encoded in the Acinetobacter baumannii genome. I hypothesized that cyclic di-GMP controls motility, biofilm formation, and desiccation tolerance in Acinetobacter baumannii. Disrupting cyclic di-GMP–modulating enzymes or cyclic di-GMP–binding effectors should alter the regulatory effectiveness of these phenotypes. I tested the multidrug-resistant isolate Acinetobacter baumannii strain AB5075 and identified several transposon …

Aggregatibacter Actinomycetemcomitans Exploits And Modulates The Immune Response By Human Neutrophils For Survival In The Anaerobic Environment., Hazel Ozuna

Electronic Theses and Dissertations

Aggregatibacter actinomycetemcomitans (Aa) is a Gram-negative facultative anaerobe and an opportunistic oral pathogen, strongly associated with localized periodontitis and other inflammatory diseases. Periodontitis is a chronic inflammation of the periodontium resulting from the inflammatory response of the host towards the dysbiotic microbial community present at the gingival crevice. The host immune response creates a hostile environment for microorganisms; therefore, it is important for Aa to be able to regulate the necessary genes to survive and thrive in such an environment. Aaexpresses several virulence factors such as a cytolethal distending toxin (Cdt), lipopolysaccharide (LPS) and leukotoxin A (LtxA), …

Characterizing The Interaction Between Candida Albicans And Two Enterobacter Species, Abigail Cornett

Electronic Theses and Dissertations

Candida albicans is the most common human fungal pathogen. The relationship between C. albicans and Enterobacter bacteria have yet to be explored. The hypothesis of this study is that C. albicans and both E. aerogenes and E. cloacae have a positive relationship and work together to infect the host. In this study, the physical cell-to-cell interaction, molecular components of said interaction, and the impact of the interaction on a live organism were explored. Results indicate that Enterobacter adheres to C. albicans and inhibits growth with unidentified secreted molecules. Als1p has potential involvement in the attachment of E. cloacae to C. …

Genistein-Enriched Pig Gut Microbiota Library As A Potential Probiotic Consortium, Theresah Amponsah

Electronic Theses and Dissertations

Plant-based diets contain numerous flavonoid compounds that produce antibacterial effects and gut health improvement. Genistein is among the most abundant isoflavones present in a plant-based diet and can be found in high amounts in soy products (up to 1g Kg-1). We describe here a robust method to identify genistein tolerant and metabolizing bacteria in swine gut microbiota and to screen the strains that have antibacterial and immunestimulatory properties. Such strains could be developed as non-antibiotic alternatives to prevent enteric infections in pigs and improve gut immunity. To this end, a mini bioreactorbased system was used to enrich genistein metabolizing bacteria …

Characterization Of Porcine Respiratory Epithelial Cells And Their Innate Immune Responses To Bacterial And Viral Ligands, Yam Prasad Gautam

Electronic Theses and Dissertations

In response to a pathogenic attack, the host produces a series of defense mechanisms through various intracellular signaling pathways. The byproduct of these signaling pathways helps tackle the invading pathogen and protects the body from getting into a diseased state. This system is called the immune system. The immune system can be divided into two branches namely the innate immune system and adaptive immune system. The groups of immune cells that provide protection regardless of the pathogen specificity constitute the innate immune system. The system that acts according to the pathogen specificity is called the adaptive immune response. The production …

E. Coli Persister Cell Survival And Rhizobia Attachment To Soybean Roots, Tanim Islam

Electronic Theses and Dissertations

The theme of this thesis revolves around how bacteria respond and thrive during stress. Chapters 1-3 are about how bacteria deal with life-threatening antibiotics. Chapter 4 covers new research on how bacteria can move from a stressful individual lifestyle (free-living bacteria) to initiating a symbiotic relationship with a plant (a less stressful lifestyle). In Chapter 1, I briefly summarize the current state of knowledge in the field of antibiotic resistance and persistence. In Chapter 2, I add to this knowledge by providing new insights into several antibiotics' potency and exploring the antibiotic Eagle effect. In Chapter 3, I use pyruvate …

Analysis Of Spore Shape Determination In Streptomyces, Ning Sun

Electronic Theses and Dissertations

Streptomycetes are Gram-positive, soil-dwelling bacteria that possess a complex life cycle with the alternation of vegetative mycelium, aerial mycelium, and spores. Streptomyces. coelicolor spore maturation is a complex process that involves spore shape metamorphosis from cylindrical pre-spores into ellipsoid spores, but the details of this process have remained enigmatic. Previously, our lab identified a novel gene ssdA that might play a role in spore shape determination using a transposon-based insertion mutagenesis in S. coelicolor. In this study, I isolated a S. coelicolor ssdA-null mutant that showed increased colony hydrophobicity and misshapen spores in sizes and shapes, confirming the …

Investigating The Development Of Fecal Bacterial Communities In Growing Dairy Calves, Emily Fowler

Electronic Theses and Dissertations

The gut development of young calves is crucial for the producer and the calf's future. Many factors can affect the development of a young calf's gastrointestinal system, and there has been little research into the fecal microbiome development of calves from 0 to 12 weeks of age. To gain further insight into this process, development of the fecal microbiome in 12 dairy calves was investigated. Fecal bacterial composition was determined at four time points (weeks 0, 4, 8 and 12) using the 16S rRNA gene through PCR-amplification of the V1-V3 regions from fecal microbial genomic DNA, followed by Illumina MiSeq …

Plasmodium Impairs Antibacterial Innate Immunity To Systemic Infections In Part Through Hemozoin-Bound Bioactive Molecules., Christopher Lynn Harding

Electronic Theses and Dissertations

Despite efforts to decrease the global health burden of malaria, infections with Plasmodium species continue to cause over 200 million episodes of malaria each year which resulted in 405,000 deaths in 2018 [1]. One complication of malaria is increased susceptibility to invasive bacterial infections. Plasmodium infections impair host immunity to non-Typhoid Salmonella (NTS) through activities of heme oxygenase I (HO-I) )-induced release of immature granulocytes and myeloid cell-derived IL-10. Yet, it is not known if these mechanisms are specific to NTS. We show here, that Plasmodium yoelii 17XNL (Py) infected mice had impaired clearance of systemic Listeria monocytogenes (Lm) during …

Identification And Structural Characterization Functional Motifs In The Porphyromonas Gingivalis Mfa1 Short Fimbria., Mohammad K. Roky

Electronic Theses and Dissertations

Porphyromonas gingivalis is a causative agent of periodontal disease, initially colonizes the oral cavity by adhering to commensal streptococci. Adherence requires the interaction of the minor fimbrial protein (Mfa1) of P. gingivalis with streptococcal antigen I/II (Ag I/II). A peptide derived from Ag I/II peptide has been well characterized and shown to significantly reduce P. gingivalis colonization and bone loss in vivo, suggesting that this interaction represents a potential target for therapeutic intervention. However, the functional motifs of Mfa1 involved in the interaction with Ag I/II remain uncharacterized. A series of N- and C-terminal peptide fragments of Mfa1 were …

Interaction Of Streptomyces Closely Associated With Bacillus In Nitrogen-Limiting Conditions, Aminya Baniya

Electronic Theses and Dissertations

Biological Nitrogen Fixation is the process of conversion of atmospheric dinitrogen into ammonia which is performed by symbiotic as well as free-living diazotrophic bacteria. A previous project to isolate free-living nitrogen fixing bacteria from a natural prairie yielded Streptomyces which grew on nitrogen free medium. Genome sequencing of three isolates revealed the presence of a second 16S rRNA gene sequence aligning with Bacillus, however repeated streaking only yielded Streptomyces colonies. The aim of this research was to characterize the interaction of three Streptomyces isolates that grow under nitrogen-free conditions, and appeared to be associated with Bacillus. The separation of Bacillus …

Genomic And Culturomic Analysis Of Gut Microbiota Function And Salmonella Enterica Expansion, Gavin Fenske

Electronic Theses and Dissertations

Enteric bacteria that are resident in the hindgut of mammals are critical in immune development, digestion, and colonization resistance against pathogens. One of the major pathogens that gut commensals provide resistance against is Salmonella enterica, a major foodborne pathogen capable of infecting almost every warm-blooded animal. Given the interplay between pathogens and commensals in the gut lumen, the gut microbiota of pigs was studied by combining two disparate techniques: shotgun metagenomics and high throughput culturomics. Metagenomics readily identifies major taxa present in samples and can give an estimation to total genetic catalogue from an environment. However, many rare or …

Genetic And Biochemical Analysis Of A Conserved, Multi-Gene System Regulation Spore-Associated Proteins In Streptomyces Coelicolor, Joseph Sallmen

Electronic Theses and Dissertations

Streptomyces coelicolor is a Gram positive, filamentous soil dwelling bacterium that exhibits a complex life cycle including the transition from a vegetative mycelium to a sporulating, aerial mycelium. Early genetic studies identified two classes of genes that resulted in developmental blocks, bald and white. The bald (bld) phenotype occurs when colonies cannot produce aerial hyphae. White (whi) colonies exhibit incomplete sporulation and/or loss of production of the concurrently produced grey pigment. While some of the original mutants have been explored, the developmental functions of many of the identified genes are not well understood. Of particular interest …

Genetic Analysis Of A Novel Ftsk Homolog, Hfka, In Streptomyces Coelicolor Development-Associated Chromosome Segregation, Sumedha Sethi

Electronic Theses and Dissertations

A quintessential phenomenon occurring during prokaryotic development is accurate segregation of the replicated genomes into the daughter cells. Key energy-dependent processes like chromosome condensation and subcellular partitioning of the genomes are driven by conserved proteins like SMC, ParB, FtsK. During its complex developmental cycle, Streptomyces coelicolor segregates its genomes into chains of unicellular spores when its multigenomic syncytial aerial hyphae undergo division.

A novel ftsK-like gene, hfkA (Homolog of FtsK protein A), was examined for function and localization during development-associated chromosome segregation. Individual deletions did not affect segregation, but a ΔhfkA ΔftsK mutant exhibited 8% anucleate …

The Q Rule In Bacteriodetes And The Identification And Characterization Of Porphyromonas Gingivalis Glutaminyl Cyclase., John Andrew Houston

Electronic Theses and Dissertations

Background: Porphyromonas gingivalis, a major pathogen associated with chronic periodontitis, secretes variety of proteins, majority of which begins with glutamine. Several of these proteins were found with pyroglutamate (pGlu) at N-terminus suggesting the presence of this posttranslational modification pathway in P.gingivalis. The observation that N-terminal glutamine is over-represented as the first amino acid after signal peptide cleavage, and subsequent confirmation of pGlu formation on the nascent protein via mass spectrometry, led us to conclude that an enzyme must be present as the executor of this reaction. Hypothesis: PG2157 is a glutaminyl cyclase and is responsible for the cyclization of …

Hydrodynamic Cavitation As In-Line Process To Control Common Dairy Sporeformers, Pratibha Chaudhary

Electronic Theses and Dissertations

Sporeforming bacteria and their endospores have the ability to survive thermal treatments and proliferate in the milk and dairy products to cause spoilages. We applied the effect of hydrodynamic cavitation in controlling these bacteria and their spores at pilot scale level. Our aim was to investigate a technology that would improve the microbial quality of milk and dairy products, and is capable of being scaled up to be adapted at industrial level. Cavitation damages the cell walls of the bacteria and their endospores (releasing dipicolinic acid, responsible for endospore resistance to extreme conditions), thereby making them susceptible to thermal treatments …

Interactions Of Arbuscular Mychorrhizal Fungi And Bacterial Endophytes On Disease Resistance Of Common Root Pathogens In Wheat, Janice L. Eibensteiner

Electronic Theses and Dissertations

Arbuscular mycorrhiza, a symbiosis between plants and fungi, help plants to capture nutrients such as phosphorus (P), nitrogen (N) and other micronutrients from the aggre in exchange for up to 20% of the fixed carbon (C) from the plant. In addition, arbuscular mycorrhizal (AM) fungi can improve the resistance against abiotic (drought, salinity), and also biotic (pathogen) stresses. Bacterial endophytes promote plant growth and yield by fixing N2 from the atmosphere, assimilating N and transfer it to the plant. Bacterial endophytes can also solubilize phosphate and stimulate plant defense responses, suppressing pathogens. The host plant provides sucrose and a favorable …