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In Situ Measurement and Correlation of Cell Density and Light Emission of Bioluminescent Bacteria
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A Nutrient-Responsive LuxR Regulator Orchestrates Effector Gene Expression Across the Legionella Genus
1The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel.
Molecular Microbiology
|July 13, 2026
Summary
LexR1, a novel regulator, controls Legionella effector gene expression. It links nutrient availability to effector delivery, coordinating bacterial virulence across species.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Gene Regulation
Background:
- Legionella pneumophila employs the Icm/Dot system for effector translocation.
- Mechanisms regulating effector-encoding genes (EEGs) in Legionella are largely unknown.
Purpose of the Study:
- Identify and characterize novel regulators of Legionella effector gene expression.
- Investigate the role of LexR1 in coordinating nutrient sensing with effector gene expression.
Main Methods:
- Genetic characterization of LexR1 in L. pneumophila.
- Electrophoretic mobility shift assays to confirm DNA binding.
- Genomic analysis across seven Legionella species.
- Investigating LexR1 regulation by RpoS and Fis.
Main Results:
- LexR1 directly activates four EEGs (lem26, lem16, ravW, legC1) in L. pneumophila.
- LexR1 activity is nutrient-dependent, stimulated by casamino acids.
- LexR1 regulatory elements are conserved and found in effector genes across Legionella species, suggesting horizontal gene transfer.
- LexR1 expression is regulated by RpoS and Fis.
Conclusions:
- LexR1 is a key regulator of effector gene expression in Legionella.
- LexR1 integrates nutrient availability signals to control effector translocation.
- LexR1 plays a conserved role in coordinating virulence across the Legionella genus.
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