Browsing by Subject "P. aeruginosa"
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item Flagella and Pili-Mediated Near-Surface Single-Cell Motility Mechanisms in P. aeruginosa(2011-04) Conrad, Jacinta C.; Gibiansky, Maxsim L.; Jin, Fan; Gordon, Vernita D.; Motto, Dominick A.Bacterial biofilms are structured multicellular communities that are responsible for a broad range of infections. Knowing how free-swimming bacteria adapt their motility mechanisms near a surface is crucial for understanding the transition from the planktonic to the biofilm phenotype. By translating microscopy movies into searchable databases of bacterial behavior and developing image-based search engines, we were able to identify fundamental appendage-specific mechanisms for the surface motility of Pseudomonas aeruginosa. Type IV pili mediate two surface motility mechanisms: horizontally oriented crawling, by which the bacterium moves lengthwise with high directional persistence, and vertically oriented walking, by which the bacterium moves with low directional persistence and high instantaneous velocity, allowing it to rapidly explore microenvironments. The flagellum mediates two additional motility mechanisms: near-surface swimming and surface-anchored spinning, which often precedes detachment from a surface. Flagella and pili interact cooperatively in a launch sequence whereby bacteria change orientation from horizontal to vertical and then detach. Vertical orientation facilitates detachment from surfaces and thereby influences biofilm morphology.Item Investigating sociomicrobiology by integrating micro 3D printing with quantitative analytical techniques(2019-02-05) Fitzpatrick, Mignon Denise; Shear, Jason B.; Brodbelt, Jennifer; Anslyn, Eric; Roberts, Sean; Hoffman, DavidAntibiotic resistant polymicrobial infections have become a source of great concern in recent years both in clinical settings as well as in basic and medical research. Incidence of resistance and increased virulence, which typically emerge within small, dense cellular ensembles on picoliter scales, is on the rise and scientists are just beginning to understand the complexity of these dangerous bacterial populations. To that end, the research in this dissertation has sought to analyze the complex social interactions of micro 3D (µ3D) printed bacterial colonies with a variety of analytical techniques. Through characterization of the µ3D printed hydrogels themselves, and by pairing this technology with fluorescence and confocal microscopy, electrochemical studies, and mass spectrometry, important insights regarding the sociomicrobiology of these bacterial communities emerge. The Shear lab has previously employed µ3D printing of bacterial aggregates to study microbial populations in environments that reproduce attributes associated with complex spatiotemporal in vivo conditions to a much greater extent than traditional culture techniques. Combining this technology with advanced imaging approaches has enabled a detailed investigation into properties of intra- and inter-species cooperation, including factors that influence antibiotic resistance and virulence. The goal of the work presented here is to integrate quantitative and qualitative analytical techniques with µ3D printing technology to enable novel approaches for studying interactions, both within and between small bacterial aggregates in complex microbial environments. This information will be vital in the next steps toward designing better and more efficient strategies for combating complex pathogenic communities that exist within polymicrobial infection environments.Item Overcoming antibiotic resistance in microbial populations : an interdisciplinary perspective(2015-08) Kaushik, Karishma Surendra; Gordon, Vernita DianeAntibiotic resistance is a major public health problem. The increase in antibiotic-resistant bacteria and decline in the approval of newer antibiotics has prompted the need for novel therapeutic approaches. In the environment and in the human body, microbes are exposed to varying spatial landscapes. Further, bacteria assemble into multicellular assemblies called biofilms, which possess intricate spatial structure. Inherent to this spatial structure, microbial communities also possess population structure, characterized by cell density, spatial organization, and different cell types. This dissertation has three main goals: i) to study the effect of microbial population structure on the survival of antibiotic resistant mutants, using P. aeruginosa, an opportunistic human pathogen as a model organism, ii) to evaluate the therapeutic potential of using bicarbonate to enhance the efficacy of aminoglycoside antibiotics, first-line agents for P. aeruginosa infections, and develop an improved method of analysis of drug interactions iii) to develop a low-cost, hands-on, educational module to characterize antimicrobial compounds using an interdisciplinary, biophysical approach.Item Tobramycin and Bicarbonate Synergise to Kill Planktonic Pseudomonas Aeruginosa, but Antagonise to Promote Biofilm Survival(Nature Partner Journals, 2016-05) Kaushik, Karishma S.; Stolhandske, Jake; Shindell, Orrin; Smyth, Hugh D.; Gordon, Vernita D.; Gordon, Vernita D.Increasing antibiotic resistance and the declining rate at which new antibiotics come into use create a need to increase the efficacy of existing antibiotics. The aminoglycoside tobramycin is standard-of-care for many types of Pseudomonas aeruginosa infections, including those in the lungs of cystic fibrosis (CF) patients. P. aeruginosa is a nosocomial and opportunistic pathogen that, in planktonic form, causes acute infections and, in biofilm form, causes chronic infections. Inhaled bicarbonate has recently been proposed as a therapy to improve antimicrobial properties of the CF airway surface liquid and viscosity of CF mucus. Here we measure the effect of combining tobramycin and bicarbonate against P. aeruginosa, both lab strains and CF clinical isolates. Bicarbonate synergises with tobramycin to enhance killing of planktonic bacteria. In contrast, bicarbonate antagonises with tobramycin to promote better biofilm growth. This suggests caution when evaluating bicarbonate as a therapy for CF lungs infected with P. aeruginosa biofilms. We analyse tobramycin and bicarbonate interactions using an interpolated surface methodology to measure the dose–response function. These surfaces allow more accurate estimation of combinations yielding synergy and antagonism than do standard isobolograms. By incorporating predictions based on Loewe additivity theory, we can consolidate information on a wide range of combinations that produce a complex dose–response surface, into a single number that measures the net effect. This tool thus allows rapid initial estimation of the potential benefit or harm of a therapeutic combination. Software code is freely made available as a resource for the community.