Two-Component Signaling System VgrRS Directly Senses Extracytoplasmic and Intracellular Iron to Control Bacterial...

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Iron is essential for cellular life but toxic in excess.
• Pathogens face iron-limited environments due to host immune responses.
• Mechanisms of iron sensing and homeostasis in bacteria are not fully understood.

Purpose of the Study:

• To elucidate the iron sensing and response mechanism in Xanthomonas campestris pv. campestris.
• To identify the roles of VgrS and VgrR in bacterial iron homeostasis.
• To understand how iron levels regulate bacterial virulence.

Main Methods:

• Comparative proteomics to identify VgrR regulon.
• Chromatin immunoprecipitation sequencing (ChIP-seq) to determine VgrR DNA binding sites.
• Analysis of gene expression and protein interactions.

Main Results:

• VgrS (ColS) senses extracytoplasmic iron limitation, while VgrR (ColR) detects intracellular iron excess.
• Phosphorylated VgrR represses transcription of the TonB-dependent receptor gene tdvA under iron-depleted conditions.
• Intracellular iron accumulation dissociates VgrR-Fe2+ interaction, relieving tdvA repression and preventing excessive iron uptake.

Conclusions:

• The VgrS-VgrR system acts as a direct sensor for both extracellular and intracellular iron.
• This signaling pathway is crucial for maintaining bacterial iron homeostasis and virulence.
• The system modulates iron uptake by regulating key genes like tdvA.