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Updated: Sep 11, 2025
Microscopy-based Assays for High-throughput Screening of Host Factors Involved in Brucella Infection of Hela Cells
Published on: August 5, 2016
A chimeric Mla-Pqi lipid transport system is required for Brucella abortus survival in macrophages
Adélie Lannoy1, Alexi Ronneau1, Miguel Fernández-García2,3
1URBM and Department of Biology, Namur Research Institute for Life Sciences (NARILIS), Namur, Belgium.
Abstract:
The cell envelope of gram-negative bacteria is composed of an inner and an outer membrane. In Escherichia coli, several pathways mediate phospholipid transport between the two membranes, including the Mla (i.e., maintenance of lipid asymmetry) and Pqi (i.e., paraquat inducible) systems. Here, we identify and characterise in the intracellular pathogen Brucella abortus a complex named Mpc, which exhibits homology to both Mla and Pqi components. Mpc is required for bacterial growth under envelope stress conditions, and for survival within macrophages during the early stages of infection. Analyses of protein-protein interactions and structural predictions suggest that the Mpc complex bridges the two membranes of the bacterial cell envelope. Absence of this system results in altered lipid composition of the outer membrane vesicles, indicating that Mpc plays a role in lipid transport between the membranes. Our sequence comparisons reveal that Mpc is conserved across numerous species of Hyphomicrobiales. The discovery of this novel lipid-trafficking system expands our understanding of the diversity and evolution of lipid-transport mechanisms in diderm bacteria.
Insights
Researchers discovered a new lipid transport system, the Mpc complex, in Brucella abortus. This system is crucial for bacterial growth under stress and survival during infection, bridging the inner and outer membranes.
Area of Science:
- Microbiology
- Cell Biology
- Bacterial Pathogenesis
Background:
- Gram-negative bacteria possess a complex cell envelope with inner and outer membranes.
- Phospholipid transport between these membranes is essential and mediated by systems like Mla and Pqi in E. coli.
Purpose of the Study:
- To identify and characterize novel lipid transport systems in the intracellular pathogen Brucella abortus.
- To investigate the role of the newly identified Mpc complex in bacterial physiology and pathogenesis.
Main Methods:
- Homology analysis to identify Mpc complex components.
- Protein-protein interaction studies and structural predictions.
- Phenotypic analysis under envelope stress and during macrophage infection.
- Analysis of outer membrane vesicle lipid composition.
Main Results:
- Identified and characterized the Mpc complex in Brucella abortus, showing homology to Mla and Pqi systems.
- Mpc is essential for bacterial growth under envelope stress and survival within macrophages.
- Structural predictions suggest Mpc bridges the inner and outer membranes.
- Absence of Mpc alters outer membrane vesicle lipid composition, indicating a role in inter-membrane lipid transport.
- Mpc is conserved in numerous Hyphomicrobiales species.
Conclusions:
- The Mpc complex represents a novel lipid-trafficking system in gram-negative bacteria.
- This discovery expands the understanding of lipid transport diversity and evolution in diderm bacteria.
- Mpc is critical for Brucella abortus virulence and adaptation to host environments.
