Mutually repressing repressor functions and multi-layered cellular heterogeneity regulate the bistable Salmonella...

Area of Science:

• Microbiology
• Bacterial genetics
• Gene regulation

Background:

• Bistable gene expression in Salmonella leads to specialized subpopulations with distinct functions.
• Flagellar gene repression aids Salmonella in evading host defenses and improving colonization.
• Bistability is defined by unstable intermediate gene expression states due to genetic circuitry.

Purpose of the Study:

• To demonstrate sustained bistable fliC expression in virulent Salmonella 14028.
• To investigate the dynamic control of flagellar gene expression by the YdiV and FliZ repressors.
• To understand the role of the YdiV-FliZ circuit in Salmonella bistability.

Main Methods:

• Demonstration of sustained bistable fliC expression in Salmonella 14028.
• Analysis of the YdiV and FliZ regulatory roles in flagellar gene expression.
• Assessment of bistability in ΔfliZ populations and ydiV-independent FliZ control.

Main Results:

• YdiV and FliZ dynamically control the distribution of flagellar gene expression.
• YdiV promotes the fliC-OFF state, while FliZ promotes the fliC-HIGH state.
• The YdiV-FliZ circuit is not essential for bistability, and regulators can independently shape fliC expression.

Conclusions:

• The YdiV-FliZ regulatory circuit fine-tunes Salmonella's binary response to environmental cues.
• This genetic circuitry coordinates regulatory heterogeneity for specialized cell functions.
• Understanding this bistability is crucial for Salmonella pathogenesis and host-pathogen interactions.