Journal article
Evidence Suggesting That Francisella tularensis O-Antigen Capsule Contains a Lipid A-Like Molecule That Is Structurally Distinct from the More Abundant Free Lipid A
PloS one, Vol.11(6), pp.e0157842-e0157842
2016
DOI: 10.1371/journal.pone.0157842
PMCID: PMC4915664
PMID: 27326857
Abstract
Francisella tularensis, the Gram-negative bacterium that causes tularemia, produces a high molecular weight capsule that is immunologically distinct from Francisella lipopolysaccharide but contains the same O-antigen tetrasaccharide. To pursue the possibility that the capsule of Francisella live vaccine strain (LVS) has a structurally unique lipid anchor, we have metabolically labeled Francisella with [14C]acetate to facilitate highly sensitive compositional analysis of capsule-associated lipids. Capsule was purified by two independent methods and yielded similar results. Autoradiographic and immunologic analysis confirmed that this purified material was largely devoid of low molecular weight LPS and of the copious amounts of free lipid A that the Francisellae accumulate. Chemical hydrolysis yielded [14C]-labeled free fatty acids characteristic of Francisella lipid A but with a different molar ratio of 3-OH C18:0 to 3-OH C16:0 and different composition of non-hydroxylated fatty acids (mainly C14:0 rather than C16:0) than that of free Francisella lipid A. Mild acid hydrolysis to induce selective cleavage of KDO-lipid A linkage yielded a [14C]-labeled product that partitioned during Bligh/Dyer extraction and migrated during thin-layer chromatography like lipid A. These findings suggest that the O-antigen capsule of Francisella contains a covalently linked and structurally distinct lipid A species. The presence of a discrete lipid A-like molecule associated with capsule raises the possibility that Francisella selectively exploits lipid A structural heterogeneity to regulate synthesis, transport, and stable bacterial surface association of the O-antigen capsular layer.
Details
- Title: Subtitle
- Evidence Suggesting That Francisella tularensis O-Antigen Capsule Contains a Lipid A-Like Molecule That Is Structurally Distinct from the More Abundant Free Lipid A
- Creators
- Jason H Barker - Inflammation Program and Department of Internal Medicine, University of Iowa, Iowa City, IA, United States of America, and Veterans Affairs Medical Center, Iowa City, IA, United States of AmericaJustin W Kaufman - Inflammation Program and Department of Internal Medicine, University of Iowa, Iowa City, IA, United States of America, and Veterans Affairs Medical Center, Iowa City, IA, United States of AmericaMichael A Apicella - Inflammation Program and Department of Microbiology, University of Iowa, Iowa City, IA, United States of America, and Veterans Affairs Medical Center, Iowa City, IA, United States of AmericaJerrold P Weiss - Inflammation Program and Department of Microbiology, University of Iowa, Iowa City, IA, United States of America, and Veterans Affairs Medical Center, Iowa City, IA, United States of America
- Resource Type
- Journal article
- Publication Details
- PloS one, Vol.11(6), pp.e0157842-e0157842
- DOI
- 10.1371/journal.pone.0157842
- PMID
- 27326857
- PMCID
- PMC4915664
- NLM abbreviation
- PLoS One
- ISSN
- 1932-6203
- eISSN
- 1932-6203
- Publisher
- Public Library of Science
- Grant note
- P30 ES005605 / NIEHS NIH HHS P01 AI044642 / NIAID NIH HHS R01 AI104728 / NIAID NIH HHS
- Language
- English
- Date published
- 2016
- Academic Unit
- Microbiology and Immunology; Infectious Diseases; Stead Family Department of Pediatrics; Internal Medicine
- Record Identifier
- 9984094208802771
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