Article

EptC of Campylobacter jejuni mediates phenotypes involved in host interactions and virulence.

Section of Molecular Genetics and Microbiology.
Infection and immunity (Impact Factor: 4.16). 11/2012; DOI: 10.1128/IAI.01046-12
Source: PubMed

ABSTRACT Campylobacter jejuni is a natural commensal of the avian intestinal tract. However, this bacterium is also the leading cause of acute bacterial diarrhea worldwide and implicated in development of Guillain-Barré syndrome. Like many bacterial pathogens, C. jejuni assembles complex surface structures that interface with the surrounding environment and are involved in pathogenesis. Recent work in C. jejuni identified a gene encoding a novel phosphoethanolamine (pEtN) transferase, EptC (Cj0256), that serves a promiscuous role in modifying the flagellar rod protein, FlgG, the lipid A domain of lipooligosaccharide (LOS) and several N-linked glycans. In this work, we report that EptC catalyzes the addition of pEtN to the first heptose sugar of the inner core oligosaccharide of LOS, a fourth enzymatic target. We also examine the role pEtN modification plays in circumventing detection and/or killing by host defenses. Specifically, we show that modification of C. jejuni lipid A with pEtN results in increased recognition by human toll-like receptor 4-myeloid differentiation factor 2 (hTLR4-MD2) complex along with providing resistance to relevant mammalian and avian antimicrobial peptides (i.e. defensins). We also confirm the inability of aberrant forms of LOS to activate toll-like receptor 2 (TLR2). Most exciting, we demonstrate that strains lacking eptC show decreased commensal colonization of chick ceca and reduced colonization of BALB/cByJ mice when compared to wild type strains. Our results indicate that modification of surface structures with pEtN by EptC is key to its ability to promote commensalism in an avian host and survive in the mammalian gastrointestinal environment.

Download full-text

Full-text

Available from: Thomas Cullen, Jun 26, 2015
0 Followers
 · 
130 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Haemophilus ducreyi resists the cytotoxic effects of human antimicrobial peptides (APs), including α-defensins, β-defensins, and the cathelicidin LL-37. Resistance to LL-37, mediated by the sensitive to antimicrobial peptide (Sap) transporter, is required for H. ducreyi virulence in humans. Cationic APs are attracted to the negatively charged bacterial cell surface. In other gram-negative bacteria, modification of lipopolysaccharide or lipooligosaccharide (LOS) by the addition of positively charged moieties, such as phosphoethanolamine (PEA), confers AP resistance by means of electrostatic repulsion. H. ducreyi LOS has PEA modifications at two sites, and we identified three genes (lptA, ptdA, and ptdB) in H. ducreyi with homology to a family of bacterial PEA transferases. We generated non-polar, unmarked mutants with deletions in one, two, or all three putative PEA transferase genes. The triple mutant was significantly more susceptible to both α- and β-defensins; complementation of all three genes restored parental levels of AP resistance. Deletion of all three PEA transferase genes also resulted in a significant increase in the negativity of the mutant cell surface. Mass spectrometric analysis revealed that LptA was required for PEA modification of lipid A; PtdA and PtdB did not affect PEA modification of LOS. In human inoculation experiments, the triple mutant was as virulent as its parent strain. While this is the first identified mechanism of resistance to α-defensins in H. ducreyi, our in vivo data suggest that resistance to cathelicidin LL-37 may be more important than defensin resistance to H. ducreyi pathogenesis.
    PLoS ONE 04/2015; 10(4):e0124373. DOI:10.1371/journal.pone.0124373 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Yersinia pestis, the causative agent of plague, can be transmitted by fleas in two different manners: by early phase transmission (EPT), which occurs shortly after flea infection, or by blocked fleas following long-term infection. Efficient flea-borne transmission is predicated upon the ability of Y. pestis to be maintained within the flea. Signature-tagged mutagenesis (STM) was used to identify genes required for Y. pestis maintenance in a genuine plague vector, Xenopsylla cheopis. The STM screen identified seven mutants that displayed markedly reduced fitness in fleas after four days, the time during which EPT occurs. Two of the mutants contained insertions in genes encoding glucose-1-phosphate uridylyltransferase (galU) and UDP-4-amino-4-deoxy-L-arabinose-oxoglutarate aminotransferase (arnB), which are involved in the modification of lipid A with aminoarabinose (Ara4N) and resistance to cationic antimicrobial peptides (CAMPs). These Y. pestis mutants were more susceptible to the CAMPs cecropin A and polymyxin B, and produced lipid A lacking Ara4N modifications. Surprisingly, an in-frame deletion of arnB retained modest levels of CAMP resistance and Ara4N modification, indicating the presence of compensatory factors. It was determined that WecE, an aminotransferase involved in biosynthesis of enterobacterial common antigen, plays a novel role in Y. pestis Ara4N modification by partially offsetting the loss of arnB. These results indicate that mechanisms of Ara4N modification of lipid A are more complex than previously thought, and these modifications, as well as several factors yet to be elucidated, play an important role in early survival and transmission of Y. pestis in the flea vector.
    Microbiology 12/2014; 161(Pt_3). DOI:10.1099/mic.0.000018 · 2.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Antimicrobial peptides (AMPs) are at the front-line of host defense during infection and play critical roles both in reducing the microbial load early during infection and in linking innate to adaptive immunity. However, successful pathogens have developed mechanisms to resist AMPs. Although considerable progress has been made in elucidating AMP-resistance mechanisms of pathogenic bacteria in vitro, less is known regarding the in vivo significance of such resistance. Nevertheless, progress has been made in this area, largely by using murine models and, in two instances, human models of infection. Herein, we review progress on the use of in vivo infection models in AMP research and discuss the AMP resistance mechanisms that have been established by in vivo studies to contribute to microbial infection. We posit that in vivo infection models are essential tools for investigators to understand the significance to pathogenesis of genetic changes that impact levels of bacterial susceptibility to AMPs. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides. Copyright © 2015. Published by Elsevier B.V.
    Biochimica et Biophysica Acta (BBA) - Biomembranes 02/2015; DOI:10.1016/j.bbamem.2015.02.012 · 3.43 Impact Factor