Acinetobacter baumannii Virulence Attributes: The Roles of Outer Membrane Protein A, Acinetobactin-mediated Iron Acquisition Functions, and Blue Light Sensing Protein A
Year: 2010
Type: article
Abstract: Acinetobacter baumannii is a gram-negative opportunistic pathogen that has emerged as a problematic organism, causing severe infections in human hosts.This is compounded by the fact that clinical isolates of this organism are often resistant to multiple types of antimicrobial therapies.To better understand the molecular mechanisms involved in pathogenicity with the long-term goal of finding targets for novel therapies of the future, the work presented in this manuscript focuses on the factors involved in the adherence to abiotic and biotic surfaces, invasion of epithelial cells, and killing of invertebrate animal models.In addition, this work presents novel data about the regulation of those factors.Adherence to biotic surfaces is often the first step of pathogenesis.It is apparent that outer membrane protein A is required for adherence of A. baumannii ATCC 19606 T cells to human respiratory epithelia.In addition, cells lacking the productionof this protein are deficient in their ability to kill eukaryotic cells such as A549 human alveolar cells and also Candida albicans tup1 filaments.Furthermore, it was proven that the death of these cells is a result of an induction of apoptosis and secreted proteins in addition to OmpA are implicated in that process.After the bacterial cell invades the A549 eukaryotic cell, it requires the function of an iron acquisition system, specifically acinetobactin biosynthesis and transport.Without these functions, bacterial cells can adhere to the surface of A549 cells, but cannot persist and replicate in the cytoplasm of the eukaryotic cell.In addition, the apoptotic induction in A549 cells is lowered when infections are performed with mutants lacking iron acquisition functions.Interestingly, A. baumannii cells lacking siderophore biosynthesis can be crossfed during LIST OF FIGURES Figure Page Biofilm assays and detection of OmpA produced by A. baumannii 19606 derivatives SEM analysis of bacterial biofilms formed on plastic surfaces at the liquid-air interface SEM analysis of bacterial attachment to C. albicans cells Bacterial adhesion and invasion of A549 alveolar epithelial cells CLSM of Live/Dead stained tup1 filaments or SC5314 yeast cells C. albicans viability assays TUNEL assays of C. albicans tup1 filaments and A549 monolayers Killing of tup1 filaments and A549 cells by cell-free bacterial culture supernatants Protease sensitivity of the cytotoxic factor(s) secreted by A. baumannii 19606 Interaction of bacteria with A549 alveolar epithelial cells Intracellular bacterial replication and utilization of the acinetobactin-mediated iron acquisition system Detection of the acinetobactin outer membrane receptor protein BauA CLSM analysis of A549 monolayers infected with A. baumannii ATCC 19606 T isogenic strains A549 apoptotic response to bacterial infection Evaluation of A549 apoptotic response to acinetobactin G. mellonella survival probability when injected with A. baumannii ATCC 19606 T isogenic strains PCR and agarose gel electrophoresis analysis of clinical isolates for the presence of the blsA gene Effect of blue light on motility in A. baumannii clinical strains Killing of C. albicans filaments by A. baumannii clinical strains Bacterial interaction with A549 human respiratory epithelia at 37°C or 24°C v TEM analysis of whole bacterial cells lifted onto formvar grids and negatively stained with ammonium molybdate to visualize extracellular structures Analysis of bacterial growth at 37°C (A) or 24°C (B) in LB broth in the presence of increasing dipyridyl concentration and either darkness or blue light Immunoblot and densitometry analysis of total membrane fractions for BauA Transcriptional analysis of bauA expression in the parental strain ATCC 17978 and 17978.OR isogenic derivative in the presence of different free iron conditions Immunoblot and densitometry analysis of total membrane fractions for OmpA Effect of BlsA and temperature in the mortality of A. baumannii in Galleria mellonella over a five-day period Model depicting the role of temperature, blue light and BlsA on the production of OmpA and BauA at 24°C and 37°C vi To my family, Josh and Zachary, whom I love above all else.
Author: Jennifer A. Gaddy
Institution: Miami University
Language: English
Subfield: Microbiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2241015369