Dataset Information

Identification of two late acyltransferase genes responsible for lipid A biosynthesis in Moraxella catarrhalis.

ABSTRACT: Lipid A is a biological component of the lipo-oligosaccharide of a human pathogen, Moraxella catarrhalis. No other acyltransferases except for UDP-GlcNAc acyltransferase, responsible for lipid A biosynthesis in M. catarrhalis, have been identified. By bioinformatics, two late acyltransferase genes, lpxX and lpxL, responsible for lipid A biosynthesis were identified, and knockout mutants of each gene in M. catarrhalis strain O35E were constructed and named O35ElpxX and O35ElpxL. Structural analysis of lipid A from the parental strain and derived mutants showed that O35ElpxX lacked two decanoic acids (C10:0), whereas O35ElpxL lacked one dodecanoic (lauric) acid (C12:0), suggesting that lpxX encoded decanoyl transferase and lpxL encoded dodecanoyl transferase. Phenotypic analysis revealed that both mutants were similar to the parental strain in their toxicity in vitro. However, O35ElpxX was sensitive to the bactericidal activity of normal human serum and hydrophobic reagents. It had a reduced growth rate in broth and an accelerated bacterial clearance at 3 h (P < 0.01) or 6 h (P < 0.05) after an aerosol challenge in a murine model of bacterial pulmonary clearance. O35ElpxL presented similar patterns to those of the parental strain, except that it was slightly sensitive to the hydrophobic reagents. These results indicate that these two genes, particularly lpxX, encoding late acyltransferases responsible for incorporation of the acyloxyacyl-linked secondary acyl chains into lipid A, are important for the biological activities of M. catarrhalis.

SUBMITTER: Gao S

PROVIDER: S-EPMC2585779 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Identification of two late acyltransferase genes responsible for lipid A biosynthesis in Moraxella catarrhalis.

Gao Song S Peng Daxin D Zhang Wenhong W Muszyński Artur A Carlson Russell W RW Gu Xin-Xing XX

The FEBS journal 20080913 20

Lipid A is a biological component of the lipo-oligosaccharide of a human pathogen, Moraxella catarrhalis. No other acyltransferases except for UDP-GlcNAc acyltransferase, responsible for lipid A biosynthesis in M. catarrhalis, have been identified. By bioinformatics, two late acyltransferase genes, lpxX and lpxL, responsible for lipid A biosynthesis were identified, and knockout mutants of each gene in M. catarrhalis strain O35E were constructed and named O35ElpxX and O35ElpxL. Structural analys ...[more]

PMID: 18795947

Similar Datasets

Project description:Moraxella catarrhalis is a major cause of acute otitis media in young children and has also been implicated as an important cause of exacerbations in adults with underlying pulmonary disease. Due to the considerable level of antibiotic resistance and the high degree of carriage rates in young children, it is likely that the incidence of M. catarrhalis infections will continue to rise. M. catarrhalis is a strict human respiratory pathogen, and this bacterium uses both transferrin and lactoferrin receptors to fulfill the essential iron requirement for survival in vivo. However, these are the only described iron acquisition systems for this organism. In this report we have demonstrated that M. catarrhalis can also utilize hemin as a sole source of iron for growth. In addition, we have identified and characterized an outer membrane protein with homology (26 to 28% similarity) to other known hemin binding and uptake proteins in related gram-negative organisms (i.e., Bordetella and Yersinia spp.). This newly described M. catarrhalis protein, termed HumA, is capable of directly binding to hemin coupled to a solid-phase matrix. M. catarrhalis HumA expressed on the surface of an Escherichia coli hemA-deficient strain (K-12 EB53) is fully capable of complementing the defect and thus restoring the ability of this strain to grow in the presence of hemin. When M. catarrhalis is grown in the presence of hemin, HumA expression is clearly increased as shown by Western blotting with polyclonal antiserum developed against a HumA peptide. In addition, growth analyses revealed that a HumA-deficient mutant of M. catarrhalis (7169::humA) is restricted for growth in the presence of hemin as the sole iron source compared to the wild-type strain. We conclude that HumA is an essential component of a hemin uptake and utilization system previously undescribed for M. catarrhalis, thus providing another mechanism of iron acquisition that may facilitate persistent colonization of the mucosal surface.

Project description:Members of the Rickettsia genus are obligate intracellular, Gram-negative coccobacilli that infect mammalian and arthropod hosts. Several rickettsial species are human pathogens and are transmitted by blood-feeding arthropods. In Gram-negative parasites, the outer membrane (OM) sits at the nexus of the host-pathogen interaction and is rich in lipopolysaccharide (LPS). The lipid A component of LPS anchors the molecule to the bacterial surface and is an endotoxic agonist of Toll-like receptor 4 (TLR4). Despite the apparent importance of lipid A in maintaining OM integrity, as well as its inflammatory potential during infection, this molecule is poorly characterized in Rickettsia pathogens. In this work, we have identified and characterized new members of the recently discovered LpxJ family of lipid A acyltransferases in both Rickettsia typhi and Rickettsia rickettsii, the etiological agents of murine typhus and Rocky Mountain spotted fever, respectively. Our results demonstrate that these enzymes catalyze the addition of a secondary acyl chain (C14/C16) to the 3'-linked primary acyl chain of the lipid A moiety in the final steps of the Raetz pathway of lipid A biosynthesis. Since lipid A architecture is fundamental to bacterial OM integrity, we believe that rickettsial LpxJ may be important in maintaining membrane dynamics to facilitate molecular interactions at the host-pathogen interface that are required for adhesion and invasion of mammalian cells. This work contributes to our understanding of rickettsial outer membrane physiology and sets a foundation for further exploration of the envelope and its role in pathogenesis.IMPORTANCE Lipopolysaccharide (LPS) triggers an inflammatory response through the TLR4-MD2 receptor complex and inflammatory caspases, a process mediated by the lipid A moiety of LPS. Species of Rickettsia directly engage both extracellular and intracellular immunosurveillance, yet little is known about rickettsial lipid A. Here, we demonstrate that the alternative lipid A acyltransferase, LpxJ, from Rickettsia typhi and R. rickettsii catalyzes the addition of C16 fatty acid chains into the lipid A 3'-linked primary acyl chain, accounting for major structural differences relative to the highly inflammatory lipid A of Escherichia coli.

Dataset Information

Identification of two late acyltransferase genes responsible for lipid A biosynthesis in Moraxella catarrhalis.

Publications

Identification of two late acyltransferase genes responsible for lipid A biosynthesis in Moraxella catarrhalis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets