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The Lipopolysaccharide of Bordetella bronchiseptica Acts as a Protective Shield against Antimicrobial Peptides PowerPoint Presentation
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The Lipopolysaccharide of Bordetella bronchiseptica Acts as a Protective Shield against Antimicrobial Peptides. Andreas Banemann, Heike Deppisch, and Roy Gross Presented by Alaric Smith. Introduction. Bordetella species pertussis and bronchiseptica are closely related

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The Lipopolysaccharide of Bordetella bronchiseptica Acts as a Protective Shield against Antimicrobial Peptides

Andreas Banemann, Heike Deppisch, and Roy Gross

Presented by Alaric Smith

introduction
Introduction
  • Bordetella species pertussis and bronchiseptica are closely related
  • Infect mammalian mammalian upper respiratory tract
  • Produce important virulence factors (adhesins, adenylate cyclase toxin, etc.
  • All virulence genes are regulated by BvgAS system
slide3
BvgAS locus is highly unstable
  • Bacteria with mutations (“phase variants”) in this locus produce no virulence factors
  • Avirulent phase variants cannot colonize respiratory epithelium
differences between the two species
Differences between the two species
  • B. pertussis is an obligate human pathogen; causes whooping cough
  • B. bronchiseptica infects a wide range of mammals
  • B. pertussis unique virulence factors (tracheal colonization factor, pertussis toxin
slide5
LPS structure varies between the two species
  • B. pertussis requires Bvg-activated factors for cell invasion
  • B. bronchiseptica is more adept at intercellular survival
characterization of virulence strategies
Characterization of virulence strategies
  • Analysis of susceptibility to antimicrobial peptides
  • These cationic peptides (such as defensins) protect against bacterial colonization
  • Are produced in a wide range of phyla
  • Arthropod and amphibian CPs were used to distinguish between the two species’ responses
comparison of susceptibility
Comparison of susceptibility
  • Wild-type B. bronchiseptica is more resistant to CPs than B. pertussis
  • Potency of the peptides studied was ranked as follows: cecropin P > cecropin B > magainine-II-amide > protamine > melittin in B. Bronchiseptica
  • In B. pertussis protamine was more effective than magainine-II-amide
slide9
HNP-1, a beta-defensin, did not affect B. bronchiseptica virulence, but significantly impaired B. pertussis
  • Previous studies have shown B. bronchiseptica to have high resistance to CPs compared to bacteria of other genera
slide11
Genetic activation of bvg locus in B. bronchiseptica increases susceptibility to CPs (except HNP1)
  • Inactivation of the same locus in B. pertussis produces milder effects
are transposon induced mutants more susceptible to cps
Are transposon-induced mutants more susceptible to CPs?
  • Transposon-induced mutants of B. bronchiseptica were created by delivery of Tn5, then antibiotically selected.
  • Mutants indistinguishable from WT in growth were compared to WT w/r/t protamine and subsequently other CP susceptibility
  • Mutants showed significantly increased sensitivities to all CTs except cecropin P
which b bronchiseptica genes are involved in sp resistance
Which B. bronchiseptica genes are involved in SP resistance?
  • Inverse PCR was used to amplify transposon-inactivated genes in mutants
  • Inactivated genes were of the wlb family, known to be involved in LPS synthesis specifically (2,3-diNAcManA and FucNAcMe) in B. pertussis
  • Inactivated gene in PS2 strain was uncharacterizable
  • Sequencing showed high homology in wlb between the two Bordetella species
confirmation of abnormal lps
Confirmation of abnormal LPS
  • In WT B. bronchiseptica, when run on a polyacrylamide gel and stained for LPS, two bands are seen (Core LPS, and LPS with O-specific side chains)
  • B. pertussis LPS lacks these side chains
  • When separated on gels, wlb-mutant B. bronchiseptica show patterns similar to WT B. pertussis
  • PS2 strain showed normal LPS profile
conclusion
Conclusion
  • Factors involved in transmembrane peptide transport affect peptide resistance in Bordetella
  • Highly charged LPS side-chains protect B. bronchiseptica from CPs.