Population Genomics And Evolution Of Pseudomonas Aeruginosa, Samara T. Choudhury

Electronic Theses & Dissertations (2024 - present)

Pseudomonas aeruginosa is a Gram-negative bacterium ubiquitous in diverse environments and an opportunistic pathogen in humans. It is a leading cause of chronic lung infections in cystic fibrosis patients and of hospital-acquired pneumonia and sepsis. With a large flexible genome and abundant mobile genetic elements, P. aeruginosa exhibits high levels of antimicrobial resistance (AMR), making it a significant public health threat. Evolutionary processes such as homologous recombination, and horizontal gene transfer generate extensive genomic diversity in this species and facilitate the spread of resistance genes. In this dissertation, I investigate the genetic and evolutionary factors shaping P. aeruginosa population structure …

Interaction Of The Gram-Positive Human Pathogen Staphylococcus Aureus With Host Lipids, Sharanya Paul

Theses and Dissertations

Staphylococcus aureus is a prominent pathogen that is known to incorporate straight-chain unsaturated fatty acids (SCUFAs) into its lipids in addition to the normally biosynthesized branched-chain fatty acids (BCFAs) and straight-chain fatty acids (SCFAs). Furthermore, it has recently been shown that the incorporation of oleic acid into S. aureus lipids significantly enhanced the growth of the organism at low temperatures due to the greater fluidity imparted to the membrane. Together with others in the Wilkinson and Dahl laboratory, I have shown that low-temperature growth is enhanced by various SCUFAs, including the human antimicrobial fatty acids sapienic acid, linoleic acid, and …

A Comparison Of White-Light And Monochromatic Led Sources For Antimicrobial Photodynamic Inactivation Of Staphylococcus Aureus, Emily Simmons

The Journal of Purdue Undergraduate Research

Drug-resistant bacteria are an ongoing public health crisis for which alternative treatments are needed. One alternative is antimicrobial photodynamic inactivation (aPDI), which uses potent photosensitizers and light irradiation to damage the bacteria. Our standard light source used in aPDI is a single-wavelength light source at 405-nm; however, we evaluated a white-light source for similarities in the resulting aPDI activities. This is done by comparing aPDI experiments using S. aureus and its methicillin-resistant strains (MRSA) conducted with either the white LED light source or the 405-nm LED light source. Statistical analysis using t-tests revealed no significant differences in the aPDI activities …

Requirement Of Prepiilin Peptidase Activity For Variovorax Paradoxus Eps Flp/Fap Pilus Assembly, Jenny L. Lanthripp

Electronic Theses, Projects, and Dissertations

Variovorax paradoxus is a Gram-negative aerobic bacterium present in both soil and the human oral microbiome. This species contributes to biotransformation of xenobiotics and promotes plant growth. Interestingly, although the genome of strain EPS lacks the flagellum operon annotated in strain S110, the microbe remains motile, and flagella can be observed microscopically. To investigate this unexpected phenotype, motility mutants were enriched from a Tn5 mutant library using a liquid culture settling strategy. A total of 122 isolates were screened for motility defects, and 57 exhibited significantly reduced motility compared to the wild type. Rescue cloning revealed that over 60% of …

Functional Analysis Of Ftsa-Mediated Recruitment Of Ftsk In Escherichia Coli, Abbigale Perkins

Dissertations and Theses (Open Access)

Bacterial cytokinesis requires precise coordination between cytoplasmic and periplasmic components of the divisome to ensure that membrane constriction and chromosome segregation occur in synchrony. The actin-like protein FtsA plays a central role in this process by tethering FtsZ to the membrane and recruiting downstream division proteins. Despite its essential function, the mechanisms by which FtsA coordinates divisome activation and the recruitment of late-acting proteins remain incompletely defined. To address this, the role of FtsA in activating septal synthesis and recruiting the DNA translocase FtsK was examined using mutational analysis in Escherichia coli.

The FtsA^{M96E R153D} variant, which has …

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 …

Investigating The Mechanisms Of Microbial Interactions Using A Model Cystic Fibrosis Polymicrobial Community, Bassam El Hafi

Dartmouth College Ph.D Dissertations

Cystic fibrosis (CF) airway microbial communities are complex ecosystems where interspecies interactions influence pathogen survival and disease progression. We leverage a CF-relevant in vitro four-species model composed of Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus sanguinis, and Prevotella melaninogenica, alongside a microbiome dataset with over 4,000 respiratory samples from publicly available sequencing data of CF patient samples, to explore the dynamics of microbial interactions in CF. On a broader scale, we performed microbial network analysis to examine how the latest modulator therapy, elexacaftor/tezacaftor/ivacaftor (ETI), might influence CF microbial communities. Our analysis revealed a reduction in node connections and …

Fostering Entrepreneurial Thinking And Practice Through Teaching And Learning Integration, Mohammad G. Sabbir

Learning and Educational Center Virtual Teaching and Learning Conference

This session explores an innovative, evidence-based approach to integrating entrepreneurial thinking into undergraduate neuroscience education through hands-on gene editing experiences. Using the commercially available Bio-Rad CRISPR/Cas9-based “Out of the Blue” kit for bacterial LacZ gene editing, students are guided not only through the scientific principles underlying modern gene editing technologies but also through the entrepreneurial challenge of replicating and manufacturing the kit using existing lab resources. This model empowers students to extend their learning beyond the classroom by engaging in cost-effective, scalable biotechnology practices—particularly valuable for institutions with limited funding. Classroom-based research demonstrates increased student engagement, deeper conceptual understanding, and …

Elucidating The Relationship Between Water Quality And Antibiotic Resistance Of Rainwater Microbes Across Western Humboldt County, Theo P. Murphy, Eve Wendley, Justice Laskowski, Tyler Paredes

Humboldt Journal of Microbiology

Limited studies have been conducted regarding the fecal contamination and microbial dispersal through rainwater, with no known studies investigating the potential connection between antibiotic resistant microbes and water quality in rainwater. This study seeks to identify the presence of a correlation between water quality and incidence of antibiotic resistance in rainwater microbes. We hypothesize that there will be a correlation between these two variables. We additionally anticipate a high incidence of fecal contamination across rural and urban collection sites alike, with fecal contamination being more prevalent in rural areas than urban locals. To determine water quality, we measured the concentration …

Evaluation Of Anti-Bacterial Efficacy Of Ginger, Resin Gum, And Nigella Sativa Irrigants Against Enterococcus Faecalis: An In Vitro Study, Iman El Ghazzawy, Leen Imad Hasbini, Reem Chamseddine, Wael Betbout, Roula Abiad

International Arab Journal of Dentistry

Objectives: To evaluate the antibacterial efficacy of Ginger, Resin Gum, and Nigella Sativa, against Enterococcus Faecalis.

Methods: Thirty-eight extracted single-rooted premolars were inoculated with E.faecalis, except the negative control, and incubated for 4 weeks. After instrumentation samples were divided into 4 groups (n=7) according to final irrigation: NaOCl+EDTA (Group A), Nigella sativa (B), Resin Gum (C), Ginger (D), plus 2 control groups (n=5): Saline (E), and Saline without bacterial inoculation (F). Cultures were collected at baseline and after irrigation.

Results: One-way ANOVA showed that in groups A-D a statistically significant reduction of bacterial load was observed at …

Clinical Applications Of Probiotics: A Comprehensive Review Of Benefits And Challenges, Riyam Wissam Hassan

Maaen Journal for Medical Sciences

Probiotics are beneficial microorganisms that help balance microbes in intestines and promote growth beneficial bacteria, they vary between bacteria, yeasts, and fungi and they are helpful to human health when taken in adequate and suitable amounts. In addition to maintaining intestinal health and help with digestion and absorption, also inhibiting development and preventing spread of harmful microorganisms. It exists in different forms, in the intestines and in the foods, products fermented, and in the pharmaceutical supplements. Because human health depends largely on the interaction between humans and these microorganisms known as probiotics, it has found that these organisms have vital …

Potential Biological Hazards In Health Clinics: Key Strategies For Enhancing Worker Safety In Malaysia, Subki Ahmad, Normah Awang, Ermie Abdull Hamid, Anuar Ithnin, Nurul Farahana Kamaludin, Noraizah Muhd Nor

Makara Journal of Health Research

Background: Biological hazards in health clinics may lead to acute or chronic health issues for healthcare workers. This study aims to identify potential biological hazards within health clinics, with a focus on the knowledge, attitude, and practice (KAP) of healthcare workers, in order to improve their safety.

Methods: Samples from environmental surfaces were collected and cultured to identify bacterial pathogens. A cross-sectional study involving 203 healthcare workers was conducted using a questionnaire derived from CDC-adapted guidelines. Descriptive analysis and multivariate regression were used to assess KAP.

Results: Bacterial growth was observed in all clinics. The Kruskal-Wallis Test …

Synergistic Cefiderocol-Containing Antibiotic Combinations Active Against Highly Drug-Resistant Acinetobacter Baumannii Patient Isolates With Diverse Resistance Mechanisms, Justin Halim, Andrew P. Keane, Jeannete Bouzo, Tope Aderibigbe, Jessica A. Chicola, Katie T. Nolan, Keertana Jonnalagadda, Jason X. Tran, Valerie J. Carabetta

Rowan-Virtua School of Osteopathic Medicine Departmental Research

BACKGROUND: Acinetobacter baumannii is a nosocomial pathogen known for rapidly developing resistance to nearly all antibiotics, including last-line agents. Cefiderocol, a novel siderophore cephalosporin, has shown in vitro activity against A. baumannii and is now used clinically, but resistance is emerging. Data on cefiderocol-based antibiotic combinations are limited.

OBJECTIVES: To evaluate the in vitro activity of cefiderocol alone and in combination with other antibiotics against XDR and PDR A. baumannii clinical isolates, and to explore resistance mechanisms underlying cefiderocol synergy.

METHODS: We tested 21 XDR/PDR clinical isolates and one NDM-1-producing strain using broth microdilution and checkerboard assays with cefiderocol and …

Determining The Impact Of Surface Roughness On Disinfection Efficacy Of Commercial Products Against Pseudomonas Aeruginosa And Staphylococcus Aureus Wet Surface Biofilms, Kayley Stallings

All Theses

Biofilms are resistant to many stressors including disinfectant treatments. Disinfection may be further complicated by biofilms formed on damaged surfaces, as the damaged parts provide bacteria a better place to attach and grow. To better understand the risks, a new method to standardize surface scratching, to emulate worn surfaces via surface roughness changes was developed. These surfaces were used to grow biofilms with an adapted standardized EPA method to determine disinfection efficacy differences on scratched and non-scratched high-density polyethylene (HDPE) and stainless steel (SS) coupons treated with commercial disinfectants [hypochlorite (CL)-based, hydrogen peroxide (HP)-based, and quaternary ammonium (QA)-based]. Post-80 grit …

Elucidation Of A Role In Biofilm Production For The Tyrosine Catabolism Pathway In Vibrio Cholerae And Analysis Of Reversible Phase Variation In Vibrio Vulnificus, Aheli S. Mukerji

LSU Doctoral Dissertations

Biofilms produced by the cholera pathogen Vibrio cholerae not only enhance its ability to survive in the environment but also allow pathogenic success of the bacterium. This organism also undergoes phase variation, switching between smooth and rugose colonial phenotypes, the latter forming much more vibrio polysaccharide (VPS) resulting in more robust biofilms and subsequently having an increased level of persistence. In a previous study, many genes were found to be upregulated in the transition from the smooth to the rugose phenotype. Here, several of these upregulated genes were investigated for their potential role in biofilm production, and an additional gene, …

Erratum: Culture Harder: Use More Specimen To Increase Methicillin-Resistant Staphylococcus Aureus Culture Yield Relative To Pcr, Arvette E. Mitchell, Arpit P. Patel, Jennifer Dicandilo, Zachary W. Rebollido, Matthew Pettengill

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

During the copyediting stage of production an error was introduced to the title of this article. This resulted in misspelling of the word ‘specimen’ in the title of the published version of the record. The correct title is ‘Culture harder: use more specimen to increase methicillin-resistant Staphylococcus aureus culture yield relative to PCR.’

Previously the title was ‘Culture harder: use more specimens to increase methicillinresistant Staphylococcus aureus culture yield relative to PCR.’

The version of record was updated to reflect this correction.

We apologise for the inconvenience.

Isolation And Selection Of Bacillus Spp. As Candidate Probiotics For Use In Chickens, Adilah Adawiah, Komang Gede Wiryawan, Anja Meryandini

Makara Journal of Science

The growth rate of chickens can be improved by using probiotics as alternatives to antibiotics. Bacillus spp. as probiotics are particularly beneficial due to ability to form spores, which remain stable as commercial products over extended periods. This study aimed to isolate and select Bacillus spp. from Jasinga soil as probiotic candidates for chickens. A total of 15 isolates obtained of these, 12 were identified as Bacillus spp based on microscopic observations and screening test including ascertaining hemolysis, protease, amylase, and cellulase activities. Only six isolates exhibited gamma hemolysis and the ability to hydrolyze proteins, starch, and cellulose. Isolates BTJ1.1, …

Detection Of Quorum-Sensing Molecules In The Mutualistic Bacteria Vibrio Fischeri Exposed To Simulated Microgravity Using Cell-Based Biosensors., Paulina Slick, Maria C. Tobarra, Alba A. Chavez, Hugo Castillo

Beyond: Undergraduate Research Journal

Bacteria flourish in multiple environments when communicating with each other in a process known as Quorum Sensing. This process is accomplished by the production of small signaling molecules referred to as Autoinducers (AI). This communication allows the bacteria to alter their gene expression in an effort to regulate their cell number, behavior, community formation and virulence. The space environment provides stressful conditions for bacteria as they are exposed to radiation and Microgravity (µG or MG) altering synthesis and concentration of Autoinducers. The purpose of this research was to expose the model system Vibrio fischeri to simulated microgravity using the recently …

Abstract 2587 Recombinant Expression And Purification Of A. Vinelandii Cown In E. Coli, Julie Takei, Cedric P. Owens, Katie Sanders, Neeraja Gajendran

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The goal of this project is to study the protein CowN in the diazotroph Azotobacter vinelandii (Av) in comparison to CowN in Gluconacetobacter diazotrophicus (Gd). Nitrogenase is an enzyme that catalyzes the reduction of nitrogen gas into ammonia in diazotrophic bacteria. In many diazotrophs, the protein CowN prevents nitrogenase inhibition from the environmental gas carbon monoxide (CO). Previous work studied CowN in the diazotroph G. diazotrophicus. In G. diazotrophicus, CowN binds to nitrogenase and weakens CO binding to its active site. The mechanism of CowN has only been investigated in G. diazotrophicus. Thus, we are interested in determining if CowN's …

Culture Harder: Use More Specimen To Increase Methicillin-Resistant Staphylococcus Aureus Culture Yield Relative To Pcr, Arvette E. Mitchell, Arpit P. Patel, Jennifer Dicandilo, Zachary W. Rebollido, Matthew Pettengill

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Methicillin-resistant Staphylococcus aureus (MRSA) causes considerable morbidity and mortality in both community-acquired and healthcare-associated infections, but detecting colonization with MRSA has been shown to improve patient outcomes in certain clinical settings. MRSA colonization detection has been carried out in a variety of ways, with molecular assays having superior sensitivity in most studies relative to culture, but culture is disadvantaged in some comparisons by utilization of low specimen volumes. We compared a commercial molecular assay to both low-volume (10 µl) and high-volume (650 µl) cultures and found that increasing the volume utilized for culture led to the detection of 25% more …