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Updated: Jun 26, 2026
07:10
A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
Temporal tuning of switch-like virulence expression resolves environmental uncertainty through phenotypic
1Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA; Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
Current Biology : CB
|June 24, 2026
Summary
Salmonella Typhimurium tunes virulence gene expression probabilistically. This allows bacteria to adapt to uncertain host environments, ensuring survival and replication within host cells.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Gene Regulation
Background:
- Gene regulatory networks adapt to environmental uncertainty.
- Intracellular bacterial pathogens face dynamic and heterogeneous host environments.
- Virulence gene regulation is crucial for bacterial survival and replication.
Purpose of the Study:
- Investigate Salmonella Typhimurium's SPI-2 gene regulation.
- Determine if SPI-2 expression is tuned to intracellular-like environments.
- Evaluate the role of SsrA and SsrB in SPI-2 regulation.
Main Methods:
- Live-cell reporters
- Single-molecule fluorescence in situ hybridization (smFISH)
- In vitro and in vivo infection models (macrophages)
Main Results:
- SPI-2 expression is bimodal in clonal populations.
- Single-cell SPI-2 activation occurs progressively and is modulated by signal strength.
- SsrA and SsrB levels control SPI-2 heterogeneity, with SsrA gating activation.
- Heterogeneous SPI-2 activation occurs during macrophage infection and is affected by phagosome acidification.
Conclusions:
- Salmonella Typhimurium probabilistically tunes SPI-2 expression to intracellular environments.
- This strategy resolves uncertainty in ambiguous host conditions.
- Bimodal gene expression allows adaptation to dynamic intracellular environments.
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