Dissertation
BffA: a novel regulator of biofilm formation in the pathogen Legionella pneumophila
Doctor of Philosophy (Ph.D.), Drexel University
Mar 2016
DOI:
https://doi.org/10.17918/00007900
Abstract
Legionella pneumophila is a Gram negative, facultative intracellular pathogen, and the causative agent of Legionnaires' disease, a severe pneumonia. Legionella is responsible for the greatest number of deaths from waterborne diseases per year in the United States, leading to an additional 18,000 hospitalizations annually. As an intracellular pathogen, L. pneumophila survives within a specialized vacuole known as the Legionella-containing vacuole (LCV) where it forms a replicative niche. Upon interaction with host cells, L. pneumophila utilizes a Type IV secretion system (T4SS) to inject over 300 secreted effectors into the host cell. Some of these effectors play crucial roles in stabilizing the LCV, recruiting endoplasmic reticulum (ER)-derived vesicles, and altering the trafficking of the LCV to avoid lysosomal death of Legionella. However, in the environment, L. pneumophila has multiple options for growth and survival including planktonic growth, intracellular replication within protozoa, and the formation of single-and multispecies biofilms. Biofilms are an important niche because they allow for enhanced survival by protecting the bacteria from antimicrobial agents and temperature fluctuations while increasing nutrient and oxygen exchange. In this work we studied two separate modes of replication for L. pneumophila, (a) biofilm formation and regulation, and (b) we developed a new method for identifying the mechanism of binding of secreted effector proteins to the LCV. We identified a putative phosphodiesterase, BffA, which appears to be involved in the regulation of biofilm formation, motility, and cellular replication of L. pneumophila. Strains deleted for bffA display hyper-biofilm growth, significantly reduced motility, and enhanced growth and replication. Additionally, we observed enhanced uptake of a [delta]-bffA strain into Acanthamoeba castellanii, which enabled this strain to outcompete wild type L. pneumophila in direct competition assays in A. castellanii. Taken together, our studies suggest a role for BffA in regulatory pathways controlling biofilm formation, motility, and replication.
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Details
- Title
- BffA
- Creators
- Courtney A. Marin
- Contributors
- Shira Ninio (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xi, 73 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Microbiology and Immunology; College of Medicine; Drexel University
- Other Identifier
- 991021888974404721