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Isolation and Characterization of Extracellular Vesicles Produced by Iron-limited Mycobacteria
Published on: October 31, 2019
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Mycobacterial Esx-3 requires multiple components for iron acquisition
Mbio
|May 8, 2014
Summary
Type VII secretion system Esx-3 is crucial for iron acquisition in mycobacteria. Even minimal export of EsxHms and EsxGms proteins by Esx-3 is sufficient for growth under low-iron conditions, challenging previous assumptions.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- Type VII secretion systems (T7SS) are essential in various bacteria, including mycobacteria.
- Esx-3 specifically facilitates iron acquisition via mycobactin in mycobacteria.
- Esx-1 is known for virulence in pathogenic mycobacteria and conjugation in Mycobacterium smegmatis.
Purpose of the Study:
- To investigate the role of individual Esx-3 components in iron acquisition under low-iron conditions.
- To re-examine the structure-function relationship of T7SS, specifically Esx-3.
- To determine the quantitative requirements for Esx-3 substrates export for function.
Main Methods:
- Construction and analysis of various esx-3 mutants in Mycobacterium smegmatis.
- Assessment of bacterial growth under low-iron conditions.
- Quantification of Esx-3 substrates (EsxHms, EsxGms) secretion using targeted mass spectrometry (MRM-MS).
Main Results:
- Several Esx-3 components are individually required for low-iron growth, but MycP3 is partially expendable.
- All tested esx-3 mutants, including ΔmycP3ms, failed to export EsxHms and EsxGms to quantifiable levels.
- Minute quantities of extracellular EsxHms and EsxGms were sufficient for iron acquisition, decoupling robust secretion from function.
Conclusions:
- The relationship between Esx-3 protein export and iron acquisition function is not absolute.
- Very low levels of Esx-3 substrate secretion can restore iron acquisition under specific conditions.
- These findings necessitate a re-evaluation of T7SS structure-function dynamics.
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