Characterization of Francisella tularensis Schu S4 mutants identified from a transposon library screened for O-antigen and capsule deficiencies

Jed A Rasmussen; Joshua R Fletcher; Matthew E Long; Lee-Ann H Allen; Bradley D Jones

doi:10.3389/fmicb.2015.00338

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Characterization of Francisella tularensis Schu S4 mutants identified from a transposon library screened for O-antigen and capsule deficiencies

Journal article

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Characterization of Francisella tularensis Schu S4 mutants identified from a transposon library screened for O-antigen and capsule deficiencies

Jed A Rasmussen, Joshua R Fletcher, Matthew E Long, Lee-Ann H Allen and Bradley D Jones

Frontiers in microbiology, Vol.6(MAY), pp.338-338

2015

DOI: 10.3389/fmicb.2015.00338

PMCID: PMC4419852

PMID: 25999917

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Abstract

The lipopolysaccharide (LPS) and O-antigen polysaccharide capsule structures of Francisella tularensis play significant roles in helping these highly virulent bacteria avoid detection within a host. We previously created pools of F. tularensis mutants that we screened to identify strains that were not reactive to a monoclonal antibody to the O-antigen capsule. To follow up previously published work, we characterize further seven of the F. tularensis Schu S4 mutant strains identified by our screen. These F. tularensis strains carry the following transposon mutations: FTT0846 ::Tn5, hemH ::Tn5, wbtA ::Tn5, wzy ::Tn5, FTT0673p / prsA ::Tn 5 , manB ::Tn5, or dnaJ ::Tn5. Each of these strains displayed sensitivity to human serum, to varying degrees, when compared to wild-type F. tularensis Schu S4. By Western blot, only FTT0846 ::Tn5, wbtA ::Tn5, wzy ::Tn5, and manB ::Tn5 strains did not react to the capsule and LPS O-antigen antibody 11B7, although the wzy ::Tn5 strain did have a single O-antigen reactive band that was detected by the FB11 monoclonal antibody. Of these strains, manB ::Tn5 and FTT0846 appear to have LPS core truncations, whereas wbtA ::Tn5 and wzy ::Tn5 had LPS core structures that are similar to the parent F. tularensis Schu S4. These strains were also shown to have poor growth within human monocyte derived macrophages (MDMs) and bone marrow derived macrophages (BMDMs). We examined the virulence of these strains in mice, following intranasal challenge, and found that each was attenuated compared to wild type Schu S4. Our results provide additional strong evidence that LPS and/or capsule are F. tularensis virulence factors that most likely function by providing a stealth shield that prevents the host immune system from detecting this potent pathogen.

Public Health

capsule

mouse virulence

innate immunity

intracellular growth

O-antigen

Francisella tularensis

transposon mutagenesis

Details

Title: Subtitle: Characterization of Francisella tularensis Schu S4 mutants identified from a transposon library screened for O-antigen and capsule deficiencies
Creators: Jed A Rasmussen - Department of Microbiology, University of Iowa Carver College of Medicine
Joshua R Fletcher - Genetics Program, University of Iowa Carver College of Medicine
Matthew E Long - Molecular and Cellular Biology Program, University of Iowa Carver College of Medicine
Lee-Ann H Allen - Department of Microbiology, University of Iowa Carver College of Medicine
Bradley D Jones - Department of Microbiology, University of Iowa Carver College of Medicine
Resource Type: Journal article
Publication Details: Frontiers in microbiology, Vol.6(MAY), pp.338-338
DOI: 10.3389/fmicb.2015.00338
PMID: 25999917
PMCID: PMC4419852
NLM abbreviation: Front Microbiol
ISSN: 1664-302X
eISSN: 1664-302X
Publisher: Frontiers Media S.A
Language: English
Date published: 2015
Academic Unit: Microbiology and Immunology; Infectious Diseases; Internal Medicine
Record Identifier: 9984083271502771

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