The bacterial cell envelope is a remarkable and complex structure that guards bacteria from their surrounding environment. A defining feature of Gram-negative bacteria is the presence of an outer membrane that encapsulates the peptidoglycan layer of these organisms. While the inner membrane is composed of glycerophospholipids, the outer membrane is a unique, asymmetric bilayer with glycerophospholipids confined to the inner leaflet and lipid A, a unique saccharolipid, localized to the outer leaflet. Lipid A is the lipid moiety of lipopolysaccharide (LPS) and anchors LPS to the bacterial surface. Bacteria have evolved various mechanisms to adapt to their unpredictable and often hostile surroundings, including strategies for remodeling their membrane architecture. Often these modifications provide resistance to components of the mammalian innate immune system and modulate host recognition of the invading microorganism. The lipid A domain of LPS is toxic to humans and potent stimulator of the innate immune system through via recognition by TLR4- MD2. A number of Gram-negative pathogens modify their lipid A structure to evade host detection. Additionally, structural alteration of lipid A and glycerophospholipids can directly impact bacterial resistance to innate immune effectors such as host antimicrobial peptides. The overall objective of this proposal is to unravel the molecular mechanisms by which Vibrio cholerae, the causative agent of the disease cholera, remodels it membrane architecture and the role this remodeling plays in virulence.
The Specific Aims of the current proposal are: (1) biochemical and genetic analysis of glycine modification of V. cholerae LPS;(2) Biochemical and genetic analysis of phosphoethanolamine modification of V. cholerae LPS;(3) elucidation of machinery required for phospholipid remodeling in V. cholerae;and (4) impact of V. cholerae membrane remodeling on the host innate immune response. The completion of these Aims will directly contribute to our understanding of how lipid remodeling/modification machinery impacts pathogenesis. Finally, from this work will come not only a better understanding of the disease cholera, but new avenues for vaccine development and the ability to generate engineered LPS structures that could serve as potential adjuvants and/or LPS antagonists.
Gram-negative bacteria are responsible for a number of human infectious diseases. This includes bacteria such as Salmonella, Escherichia coli, Pseudomonas, Helicobacter pylori, and Vibrio cholerae. On the surface of these bacteria is a unique molecule called lipopolysaccharide or LPS. Much like armor, LPS helps to protect the bacterium from their surrounding environment. LPS is toxic to humans and activates the immune response. Often, gram-negative bacteria modify their LPS structure to evade detection and resist various defenses of the immune system. This application will help determine how bacteria associated with human disease modify their LPS structure possibly leading to novel therapies.
|Nowicki, Emily M; O'Brien, John P; Brodbelt, Jennifer S et al. (2014) Characterization of Pseudomonas aeruginosa?LpxT reveals dual positional lipid A kinase activity and co-ordinated control of outer membrane modification. Mol Microbiol 94:728-41|
|Moreira, Cristiano G; Herrera, Carmen M; Needham, Brittany D et al. (2013) Virulence and stress-related periplasmic protein (VisP) in bacterial/host associations. Proc Natl Acad Sci U S A 110:1470-5|
|Maue, Alexander C; Mohawk, Krystle L; Giles, David K et al. (2013) The polysaccharide capsule of Campylobacter jejuni modulates the host immune response. Infect Immun 81:665-72|
|Cullen, Thomas W; O'Brien, John P; Hendrixson, David R et al. (2013) EptC of Campylobacter jejuni mediates phenotypes involved in host interactions and virulence. Infect Immun 81:430-40|
|Hankins, Jessica V; Madsen, James A; Needham, Brittany D et al. (2013) The outer membrane of Gram-negative bacteria: lipid A isolation and characterization. Methods Mol Biol 966:239-58|
|Gattis, Samuel G; Chung, Hak Suk; Trent, M Stephen et al. (2013) The origin of 8-amino-3,8-dideoxy-D-manno-octulosonic acid (Kdo8N) in the lipopolysaccharide of Shewanella oneidensis. J Biol Chem 288:9216-25|
|Needham, Brittany D; Carroll, Sean M; Giles, David K et al. (2013) Modulating the innate immune response by combinatorial engineering of endotoxin. Proc Natl Acad Sci U S A 110:1464-9|
|Pride, Aaron C; Herrera, Carmen M; Guan, Ziqiang et al. (2013) The outer surface lipoprotein VolA mediates utilization of exogenous lipids by Vibrio cholerae. MBio 4:e00305-13|
|Cullen, Thomas W; Madsen, James A; Ivanov, Petko L et al. (2012) Characterization of unique modification of flagellar rod protein FlgG by Campylobacter jejuni lipid A phosphoethanolamine transferase, linking bacterial locomotion and antimicrobial peptide resistance. J Biol Chem 287:3326-36|
|Madsen, James A; Cullen, Thomas W; Trent, M Stephen et al. (2011) IR and UV photodissociation as analytical tools for characterizing lipid A structures. Anal Chem 83:5107-13|
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