Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Jun;62(Pt 6):807-812.
doi: 10.1099/jmm.0.056846-0. Epub 2013 Mar 8.

Late Acyltransferase Genes lpxX and lpxL Jointly Contribute to the Biological Activities of Moraxella Catarrhalis

Affiliations
Free PMC article

Late Acyltransferase Genes lpxX and lpxL Jointly Contribute to the Biological Activities of Moraxella Catarrhalis

Song Gao et al. J Med Microbiol. .
Free PMC article

Abstract

Lipo-oligosaccharide (LOS) is a major surface component and virulence factor of the human respiratory pathogen Moraxella catarrhalis. Two late acyltransferase genes, lpxX and lpxL, have been identified involved in the incorporation of acyloxyacyl-linked secondary acyl chains into lipid A during M. catarrhalis LOS biosynthesis. In this study, a double mutant with a deletion of both the lpxX and lpxL genes in M. catarrhalis strain O35E was constructed and named O35ElpxXL. Structural analysis of lipid A showed that the O35ElpxXL mutant lacked two decanoic acids (10 : 0) and one dodecanoic (lauric) acid (12 : 0). In comparison with the O35E parental strain and the single mutants O35ElpxX and O35ElpxL, the double mutant O35ElpxXL displayed prominently decreased endotoxin content, reduced resistance to normal human serum and accelerated bacterial clearance at 0, 3 and 6 h after an aerosol challenge in a mouse model of bacterial pulmonary clearance. These results indicate that these two genes encoding late acyltransferases responsible for lipid A biosynthesis jointly contribute to the biological activities and pathogenicity of M. catarrhalis. The double mutant O35ElpxXL with dramatically reduced toxicity is proposed as a potential vaccine candidate against M. catarrhalis infections for further investigation.

Figures

Fig. 1.
Fig. 1.
Composition and structural analysis of the O35ElpxXL LOS. (a) GC-MS profile of the fatty acid methyl esters obtained from lipid A of M. catarrhalis mutant O35ElpxXL. Lipid A of O35ElpxXL did not contain decanoic acid (10 : 0) or dodecanoic (lauric) acid (12 : 0). The asterisk indicates impurities. tr, Trace. (b) MALDI-TOF analysis of lipid A from O35ElpxXL and its proposed structure. The analysis was carried out in negative mode, and all ions are represented as deprotonated [M-H] ions. Lipid A of the O35ElpxXL mutant was tetra-acylated and lacked two 10 : 0 residues and one 12 : 0 residue with a structure at m/z 1416.60. (c) MALDI-TOF MS spectrum for the OS from the O35ElpxXL mutant. The analysis was carried out in positive reflectron mode.
Fig. 2.
Fig. 2.
Silver-stained SDS-PAGE pattern of LOS. Extracts from proteinase K-treated whole-cell lysates of wild-type strain O35E (lane 1), O35ElpxX (lane 2), O35ElpxL (lane 3), O35ElpxXL (lane 4) and O35ElpxXL revertant with an lpxX expression plasmid, pWlpxX (lane 5) (1.9 µg protein content) were subjected to SDS-PAGE, followed by silver staining. The positions of molecular mass markers (Mark12; Life Technologies) are indicated on the left.
Fig. 3.
Fig. 3.
Bactericidal resistance and mouse pulmonary clearance of parental strain O35E and the O35ElpxXL mutant. (a) The bactericidal activity of NHS against strain O35E (open bars) and O35ElpxXL (filled bars) are shown. HI indicates 25.0 % heat-inactivated (56 °C, 30 min) NHS used as a control for each strain tested. The data represent the means±sd of three independent experiments. (b) Time course of bacterial recovery from mouse lungs after aerosol challenges with the parental O35E (□) and mutant O35ElpxXL (▪). Each time point represents the geometric mean±sd of bacterial c.f.u. from eight mice. *P<0.05; **P<0.01.

Similar articles

See all similar articles

Cited by 2 articles

  • Panel 6: Vaccines.
    Pettigrew MM, Alderson MR, Bakaletz LO, Barenkamp SJ, Hakansson AP, Mason KM, Nokso-Koivisto J, Patel J, Pelton SI, Murphy TF. Pettigrew MM, et al. Otolaryngol Head Neck Surg. 2017 Apr;156(4_suppl):S76-S87. doi: 10.1177/0194599816632178. Otolaryngol Head Neck Surg. 2017. PMID: 28372533 Free PMC article. Review.
  • Molecular mechanisms of moraxella catarrhalis-induced otitis media.
    Hassan F. Hassan F. Curr Allergy Asthma Rep. 2013 Oct;13(5):512-7. doi: 10.1007/s11882-013-0374-8. Curr Allergy Asthma Rep. 2013. PMID: 23934577 Review.

Publication types

MeSH terms

Feedback