1. Microbiology and Infectious Disease
Download icon

The Acinetobacter baumannii Mla system and glycerophospholipid transport to the outer membrane

  1. Cassandra Kamischke
  2. Junping Fan
  3. Julien Bergeron
  4. Hemantha D Kulasekara
  5. Zachary D Dalebroux
  6. Anika Burrell
  7. Justin M Kollman
  8. Samuel I Miller  Is a corresponding author
  1. University of Washington, United States
Research Article
  • Cited 27
  • Views 3,190
  • Annotations
Cite this article as: eLife 2019;8:e40171 doi: 10.7554/eLife.40171

Abstract

The outer membrane (OM) of Gram-negative bacteria serves as a selective permeability barrier that allows entry of essential nutrients while excluding toxic compounds, including antibiotics. The OM is asymmetric and contains an outer leaflet of lipopolysaccharides (LPS) or lipooligosaccharides (LOS) and an inner leaflet of glycerophospholipids (GPL). We screened Acinetobacter baumannii transposon mutants and identified a number of mutants with OM defects, including an ABC transporter system homologous to the Mla system in E. coli. We further show that this opportunistic, antibiotic-resistant pathogen uses this multicomponent protein complex and ATP hydrolysis at the inner membrane to promote GPL export to the OM. The broad conservation of the Mla system in Gram-negative bacteria suggests the system may play a conserved role in OM biogenesis. The importance of the Mla system to Acinetobacter baumannii OM integrity and antibiotic sensitivity suggests that its components may serve as new antimicrobial therapeutic targets.

Article and author information

Author details

  1. Cassandra Kamischke

    Department of Microbiology, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  2. Junping Fan

    Department of Microbiology, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  3. Julien Bergeron

    Department of Biochemistry, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  4. Hemantha D Kulasekara

    Department of Microbiology, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  5. Zachary D Dalebroux

    Department of Microbiology, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  6. Anika Burrell

    Department of Biochemistry, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  7. Justin M Kollman

    Department of Biochemistry, University of Washington, Seattle, United States
    Competing interests
    The authors declare that no competing interests exist.

  8. Samuel I Miller

    Department of Microbiology, University of Washington, Seattle, United States
    For correspondence
    millersi@uw.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1638-2181

Funding

National Institute of Allergy and Infectious Diseases (U19AI107775)

  • Samuel I Miller

National Institutes of Health (R01GM118396)

  • Justin M Kollman

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Tâm Mignot, Aix Marseille University-CNRS UMR7283, France

Publication history

  1. Received: July 17, 2018
  2. Accepted: January 11, 2019
  3. Accepted Manuscript published: January 14, 2019 (version 1)
  4. Version of Record published: February 6, 2019 (version 2)

Copyright

© 2019, Kamischke et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 3,190
    Page views
  • 504
    Downloads
  • 27
    Citations

Article citation count generated by polling the highest count across the following sources: Scopus, Crossref, PubMed Central.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Download citations (links to download the citations from this article in formats compatible with various reference manager tools)

Open citations (links to open the citations from this article in various online reference manager services)

Categories and tags

Further reading

    1. Microbiology and Infectious Disease
    2. Structural Biology and Molecular Biophysics

    Malaria parasites use a soluble RhopH complex for erythrocyte invasion and an integral form for nutrient uptake

    Marc A Schureck et al.
    Research Article Updated

    Malaria parasites use the RhopH complex for erythrocyte invasion and channel-mediated nutrient uptake. As the member proteins are unique to Plasmodium spp., how they interact and traffic through subcellular sites to serve these essential functions is unknown. We show that RhopH is synthesized as a soluble complex of CLAG3, RhopH2, and RhopH3 with 1:1:1 stoichiometry. After transfer to a new host cell, the complex crosses a vacuolar membrane surrounding the intracellular parasite and becomes integral to the erythrocyte membrane through a PTEX translocon-dependent process. We present a 2.9 Å single-particle cryo-electron microscopy structure of the trafficking complex, revealing that CLAG3 interacts with the other subunits over large surface areas. This soluble complex is tightly assembled with extensive disulfide bonding and predicted transmembrane helices shielded. We propose a large protein complex stabilized for trafficking but poised for host membrane insertion through large-scale rearrangements, paralleling smaller two-state pore-forming proteins in other organisms.

    1. Immunology and Inflammation
    2. Microbiology and Infectious Disease

    Single-cell RNA-seq reveals transcriptomic heterogeneity mediated by host-pathogen dynamics in lymphoblastoid cell lines

    Elliott D SoRelle et al.
    Research Article

    Lymphoblastoid Cell Lines (LCLs) are generated by transforming primary B cells with Epstein-Barr Virus (EBV) and are used extensively as model systems in viral oncology, immunology, and human genetics research. In this study, we characterized single-cell transcriptomic profiles of five LCLs and present a simple discrete-time simulation to explore the influence of stochasticity on LCL clonal evolution. Single-cell RNA sequencing (scRNA-seq) revealed substantial phenotypic heterogeneity within and across LCLs with respect to immunoglobulin isotype; virus-modulated host pathways involved in survival, activation, and differentiation; viral replication state; and oxidative stress. This heterogeneity is likely attributable to intrinsic variance in primary B cells and host-pathogen dynamics. Stochastic simulations demonstrate that initial primary cell heterogeneity, random sampling, time in culture, and even mild differences in phenotype-specific fitness can contribute substantially to dynamic diversity in populations of nominally clonal cells.

    1. Evolutionary Biology
    2. Microbiology and Infectious Disease

    Collateral sensitivity associated with antibiotic resistance plasmids

    Cristina Herencias et al.
    Short Report Updated

    Collateral sensitivity (CS) is a promising alternative approach to counteract the rising problem of antibiotic resistance (ABR). CS occurs when the acquisition of resistance to one antibiotic produces increased susceptibility to a second antibiotic. Recent studies have focused on CS strategies designed against ABR mediated by chromosomal mutations. However, one of the main drivers of ABR in clinically relevant bacteria is the horizontal transfer of ABR genes mediated by plasmids. Here, we report the first analysis of CS associated with the acquisition of complete ABR plasmids, including the clinically important carbapenem-resistance conjugative plasmid pOXA-48. In addition, we describe the conservation of CS in clinical E. coli isolates and its application to selectively kill plasmid-carrying bacteria. Our results provide new insights that establish the basis for developing CS-informed treatment strategies to combat plasmid-mediated ABR.