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 …

Sporicidal Activity Mechanism Of Lactic Acid And Peracetic Acid On Bovine Pathogenic Bacillus Cereus Spores, Xin Zhang, Yunjiao Chen, Jingjing Zhao, Haiying Zheng, Lanlan Liu, Wei Liu, Mingshan Fu, Weijuan Jia, Zelin Jia, Jiayu Cui, Yuhang Zhang, Huisheng Xiong, Yujie Ma, Xueli Wang, Haifeng Wang

The Thai Journal of Veterinary Medicine

In recent years, the pathogenicity of Bacillus cereus (B. cereus) has increased significantly, its host adaptability has continued to expand, and the infection spectrum has also expanded. At the same time, food contamination by B. cereus is also common. Therefore, it is of practical significance to select green, safe and effective inhibitors. Lactic acid (LA) and peroxyacetic acid (PAA) possess good antibacterial properties, making them environmentally friendly, safe, and non-toxic. The purpose of this experiment was to preliminarily explore the inhibition mechanism of LA and PAA on B. cereus spores. The effects of LA and PAA on B. …

Investigation Of Biofilm Formation And Osmotic Stress Tolerance Of Nonmotile Escherichia Coli In Simulated Microgravity, Tyler Jenkins

Discovery Day - Daytona Beach

Simulated microgravity presents multiple physiological stressors for astronauts, including bone demineralization, muscle loss, and weakening of the immune system. Bacteria serve as viable model organisms to study physiological changes because of their abundance in the human digestive system and skin. Motility in bacteria plays a significant role in cell survival, but few studies have been conducted on microgravity’s effect on motility phenotypes. While motile strains like Escherichia coli K12 have been studied extensively under microgravity conditions, the effects of simulated microgravity on non-motile strains are largely unknown. To better understand this relationship, the nonmotile E. coli MG1655 strain was inoculated …

Effects Of Microgravity And Gamma Radiation On Biofilm Growth, Anya Pavlidis, Kaitlyn Mills Mills, Eva Mcclory, Grant Erlinder, Allen Qiu

Discovery Day - Daytona Beach

Biofilms are collections of bacteria that commonly grow on a variety of surfaces. They are resistant to environmental impacts as bacteria fortify themselves to a surface. Biofilms are commonly found on Earth, but more problematically are also found on spacecraft. On the ISS biofilms have developed in spaces like the workout area, food spaces, and most concerning in the Water Recovery System (WRS). Biofilms tend to react differently to attempted cleaning methods in space than they do on Earth and can be located in extremely difficult to reach places.   This study aims to explore the effects of gamma radiation on …

Function And Regulation Of Long Polar Fimbriae During Enterohemorrhagic Escherichia Coli Infection, Walter J. Galdamez

Dissertations and Theses (Open Access)

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that causes severe gastrointestinal disease and hemolytic uremic syndrome. EHEC employs multiple virulence factors to colonize the host intestine, including the locus of enterocyte effacement (LEE) encoded type III secretion system, intimin, and flagella, yet the role of long polar fimbriae (Lpf) in adhesions and infection remains less well understood. Long polar fimbriae can mediate bacterial attachment to host cells in vitro, yet the regulation and function of its two fimbrial operons, lpf1 and lpf2 in vivo remain poorly understood. Preliminary RNA-seq data from zebrafish infected with EHEC reveal that expression of …

Analysis Of The Atypical Temperature Dependence And Conformational Changes During Turnover Of A Lactobacillus Chlorogenic Acid Esterase, Nathaniel Carl, Yianni Tsigaris, Dan Ji, Nora K. Anpree, Kellie K. Omori, Cedric P. Owens

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Many bacterial chlorogenic acid esterases (ChlEs) exhibit atypical temperature behavior, featuring activities that barely change with temperature and activity maxima that fall below the thermal denaturation point. This work focuses on a ChlE from Lactobacillus helveticus (Lh–ChlE), which has a flat temperature dependence. First, it was determined that conformational changes during Lh–ChlE turnover are not rate-limiting and that the overall rate depends on the chemical step at all temperatures. Next, Lh–ChlE’s temperature dependence was investigated using a conformational equilibrium model that assumes the existence of a temperature-dependent equilibrium between an active and an inactive conformation and an activation heat capacity …

In Vivo Expression Profiling Of Listeria Monocytogenes Internalins (Inlf, Inlp, Inlj) And Their Corresponding Host Receptors (Vim, Afdn, Muc2) Using A Rabbit Ligated Intestinal Loop Model, Nawar Al-Janabi, Nadhim Mushtaq Hashim Al-Bderee, Zahraa M. Madania, Mohanad Jawad Kadhim

Karbala International Journal of Modern Science

Listeria monocytogenes is a Gram-positive pathogen that causes severe infections, particularly in immunocompromised individuals. Internalin genes are important virulence factors that facilitate the bacterium's invasion of host cells. This research aimed to quantify in vivo expression of selected internalin genes (inlF, inlP, and inlJ) and their corresponding host receptors (VIM, AFDN, and MUC2) during L. monocytogenes infection. To achieve this aim, a rabbit ligated intestinal loop model was constructed comprising two intestinal loops. The first loop was injected with 1 mL of L. monocytogenes (1 × 10⁷ CFU/mL), while the second loop was injected with 1 mL of PBS as …

Homocysteine Thiolactone From Translation Proofreading Is An Endogenous Ligand For Cell-Cell Signaling By The Receptor Sdia, Lorenzo Eugenio Leiva, Roberto A. Zúñiga, Gregory J. Phillips, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Several widespread mechanisms enable cellular communication and coordinate the behavior of bacterial populations. The modules responsible for cellular communication are often found in matching pairs: an enzyme that synthesizes a signal molecule and a specific receptor that decodes it. A notable exception is Escherichia coli SdiA, a homolog of known N-acyl-homoserine lactone (AHL) receptors, for which no corresponding AHL synthase exists. SdiA is an orphan receptor that enables cross-talk by sensing AHLs from other bacterial species. In this work, we investigated whether homocysteine thiolactone (HTL), an AHL-like molecule arising from a proofreading reaction of methionyl tRNA synthetase (MetRS) to correct …

Recovering Plasmid-Id Barcoded Strains Of Sinorhizobium Meliloti From A Native Soil Microbiome, Kenny Sacks, Hannah Murray, Katy Heath

MICRO-CCS student projects

Introduction

Legume-Rhizobia Mutualism: Nitrogen is an essential nutrient for plant growth. Plants can’t produce nitrogenous compounds. Rhizobia fix atmospheric nitrogen gas into bioavailable forms. Rhizobia form a nutrient exchange mutualism with leguminous plants.

Project description

Can our bacteria persist within the rhizosphere and into the nodule when faced with native microbial competitors? The Medicago-Sinorhizobium mutualism is used as a model system. Survival of strains post competition is difficult to measure due to identical 16S rRNA sequences and similar marker genes. Plasmid-ID barcoding sequences may provide a way of testing strains against a community.

Screening A Random Hile Mutant Library To Characterize Hild Regulation In Salmonella, Danista Kannah, Gracious Donkor, James M. Slauch

MICRO-CCS student projects

Salmonella is a leading cause of gastrointestinal diseases globally. It utilizes a type three secretion system (T3SS) encoded on Salmonella Pathogenicity Island 1 (SPI1) to invade host intestinal epithelial cells during infection.

HilE directly regulates HilD via a direct protein-protein interaction. The Slauch lab identified two HilD variants, A141V and A141T, which are blind to HilE. These variants activate hilA expression even in the presence of HilE, indicating that the binding of HilE to these mutants is compromised.

Hypothesis: Performing random mutagenesis of hilE could lead to changes at the protein level which could compensate for the loss of interaction …

Efficacy And Evolutionary Dynamics Of 222 Nm Far-Uvc Against Vibrio Cholerae, Kadicha Madakimova, Angus Wu, Nkrumah Grant

MICRO-CCS student projects

The Far-UVC light at 222 nm wavelength (UV222) is one of the emerging methods of disinfection of bacteria in public spaces such as hospitals and labs.

• Does not penetrate human skin and does not cause harm to eyes making it a safer alternative to conventional UV systems.

• Primarily targets proteins preventing regrowth and repair pathways.

However, the potential for bacterial adaptation following sublethal UV222 exposure remains largely unknown.

Central question: How does QS transcriptional state influence the efficacy and resistance profile of V. cholerae to UV222 nm irradiation?

Hypothesis: Qurom-sensing transcriptional state determines V. cholerae susceptibility to UV222 nm UV …

A Tale Of Two Symbionts: Comparative Cellular Localization Of Two Manipulative Rickettsiella Strains In A Spider, Kaitlyn Costanza, Thea Bliss, Matthew Doremus

MICRO-CCS student projects

Many arthropods harbor maternally transmitted endosymbionts that manipulate host reproduction to increase their transmission. One such manipulation is cytoplasmic incompatibility (CI), in which embryos produced by infected males and uninfected females fail to develop.

Rickettsiella has recently been discovered to cause CI in Mermessus fradeorum. Two geographically distinct Rickettsiella strains infect this spider: R1 causes strong CI, whereas R2 causes weaker CI.

Hypothesis: H1: Both Rickettsiella strains will localize within or near developing sperm cells in the testes. H2: The stronger R1 strain will exhibit more consistent localization within infected adult reproductive tissues than the weaker R2 strain.

Endophytic Actinobacteria: Deciphering Therapeutic And Industrial Potential, And Prospects Of Genome Mining In Novel Products Discovery, Yusra Waheed, Rabia Shahdin, Imran Sajid

Journal of Bioresource Management

Endophytic actinobacteria are a diverse group of Gram-positive bacteria with high G+C content, which inhabit plants’ internal tissues, and represent a significant yet underexplored reservoir of bioactive secondary metabolites. In host plants, a remarkable repertoire of metabolites, including broad-spectrum antibiotics, anticancer, antiviral, antifungal, antioxidant, and immunomodulatory compounds, is synthesized by these microbial allies, carrying significant medicinal and agricultural potential. These endophytes, in contrast to their soil relatives, have developed unique biosynthetic gene clusters (BGCs) strongly influenced by plant-associated factors, leading to the production of structurally novel metabolites. In recent years, the advances in genome mining, metagenomics, and metabolomics have accelerated …

Dual-Action Antibacterial Agents Targeting Biofilm Reduction And Membrane Disruption In Staphylococcus Aureus, Rahmat Folashade Zakariyah, Waliyullahi Akorede Husain, Elohor Precious Samuel, Wonder Olanipekun Oloruntoba, Fatmah Opeyemi Saka, Khalid Ayinde Oyelami, Mariam Temitope Baker

Al-Bahir

Antimicrobial resistance in Staphylococcus aureus is a serious global health problem as the organism rapidly develops resistance against widely used antibiotics. This study sought to investigate the antibacterial and antibiofilm properties of γ-Tocopherol, a natural compound from Ocimum gratissimum, as well as its synergism with 5-hydroxymethylfurfural (5-HMF) against S. aureus. The antibacterial activities and minimum inhibitory concentrations of the compounds were determined using agar diffusion and microbroth dilution methods, respectively. Biofilm reduction was evaluated using 2,3,5-triphenyltetrazolium chloride (TTC) assay and membrane integrity was evaluated using the crystal violet microtiter plate assay and the ion leakage assay. The results …

Descriptive Comparative Analysis Of Bacteriophage And Auxiliary Metabolic Gene Diversity In Marine And Wastewater Environments, Andrew Crawford

Undergraduate University Honors Capstones

Bacteriophages (phages) are viruses that infect bacteria and play a role in bacterial evolution. Through horizontal gene transfer (HGT), phages integrate parts of their genomes into their bacterial hosts. While the molecular mechanisms of this process are well understood, the evolutionary impacts remain less certain. One evolutionary explanation is that auxiliary metabolic genes (AMGs) modulate host gene expression to favor phage reproduction or improve the host’s survival. AMG can persist in hosts' or phages' genomes across future generations, altering their contributions to the ecosystem and posing a concern for human and environmental health. The objective of this project is to …

Urea-Based Boronium Salts As Antimicrobial Agents, Gabriel Allen Merchant

Honors Theses

Quaternary ammonium compounds (QACs) are widely used in disinfectants due to their ability to inhibit the growth of and eliminate microbes. The potency, broad-spectrum activity, and low cost of QACs have made them a cornerstone of modem hygiene. In recent years, QACs have garnered many health and safety concerns due to their overuse and subsequent accumulation in the environment. The increased use of QACs has further led to an increase in antimicrobial-resistant bacteria, making the synthesis of novel antibacterial compounds vital to combat this growing threat. Recent advances in boronium salts offer a unique alternative to address these adverse effects. …

Genome-Wide Phenotypic Characterization Of Mycobacteriophage Mercurio, Tyler Downs

Departmental Honors & Graduate Capstone Projects

Bacteriophages, or phages, are being piloted as a supplemental or alternative therapeutic to antibiotics against drug-resistant Mycobacterium pathogens, such as M. tuberculosis, which pose a global public health crisis.  Characterizing bacteriophage genomes can provide insights into efficacy in phage therapy before implementation or elucidate new targets to manipulate bacterial growth.  Overexpression of individual phage genes is useful to study a gene product’s function independent of others.  Here, the results of phage Mercurio plasmid library overexpression in plate-based assays are described.  Mercurio infects nonpathogenic Mycobacterium smegmatis and is genetically related to bacteriophages infecting pathogenic Mycobacterium species.  Eleven gene products of …

Understanding The Role Of Toxs As A Bile Sensing Component Of The Toxrs Virulence Regulatory System In Vibrio Spp., Minje Kim

Dartmouth College Ph.D Dissertations

Pathogenic Vibrio bacteria, such as V. cholerae and V. parahaemolyticus, colonize in the human small intestine to cause severe gastrointestinal disease. During the infection, these bacteria encounter bile salts, antimicrobial cholesterol metabolites secreted into the intestine. Pathogenic Vibrio species have evolved to utilize bile salts as signals to regulate virulence. The signaling depends in part on ToxRS, a conserved co-component transmembrane transcription regulator. ToxRS consists of the transcription factor ToxR and its membrane-tethered binding partner ToxS. ToxS is required for ToxR stability and full transcriptional activity. Although bile salts are known to influence ToxRS-dependent virulence gene expression, the molecular …

Investigating The Synthesis And Antibacterial Activity Of A Main-Chain Cationic Polymer, Emily Smith

Honors Theses

Antibiotic resistance is a growing threat to public health. Due to the overuse of antibiotics in agriculture, the overprescription of antibiotics, and the misuse of antibiotics by patients, antibiotic resistance is spreading at an alarming rate. As antibiotic resistance spreads, the antibiotics we depend on to treat common infections become ineffective. Therefore, it is imperative to develop novel treatments for infections that do not increase the prevalence of antibiotic resistance. One treatment being explored is the use of synthetic polymers with antibacterial properties. Synthetic polymers are advantageous because they can be synthesized from widely available precursors and their structure is …

Garlic Breath And Beads Of Sweat: The Effects Of Garlic And Chili Peppers On The Growth And Ph Of Streptococcus Mutans., Lena Pitzer

Honors Projects

The purpose of this project is to provide a quantifiable and repeatable measurement of how the presence of garlic and chili pepper during the growth of a carious dentine strain of Streptococcus mutans affects the growth of the strain and surrounding pH level.This research project examines two possible alternative agents, garlic and chili peppers, due to the known antimicrobial effects of their active components, allicin and capsaicin. Prepared garlic and chili extracts were used during disk diffusion to assess and measure the zones of inhibition. The anticipated results are that there will be inhibition present with both the garlic and …