Surface Sensing for Paenibacillus sp. NAIST15-1 Flagellar Gene Expression on Solid Medium

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Physiology

Background:

• Bacteria adapt to surfaces using behaviors like motility and biofilm formation.
• Surface sensing mechanisms and gene induction for surface growth are not fully understood.
• Swarming motility, crucial for surface colonization, is flagellum-dependent.

Purpose of the Study:

• To investigate the mechanism by which *Paenibacillus* sp. senses surfaces and induces motility genes.
• To identify genes critical for surface motility in *Paenibacillus* sp.
• To elucidate the role of the DegSU two-component system in regulating flagellar gene transcription.

Main Methods:

• Transposon mutagenesis to identify motility-related genes.
• Analysis of flagellar gene promoter activity.
• Gene expression analysis under varying conditions (liquid vs. solid medium, presence of viscous agents, stator gene disruption).
• Overexpression studies of the DegSU system.

Main Results:

• *Paenibacillus* sp. exhibits hyperflagellation and increased flagellar gene transcription on solid medium.
• Mutations in *degSU*, *wsfP*, or *PBN151_4312* abolished flagellin synthesis and reduced flagellar gene transcription.
• Flagellar gene transcription is induced by restricted flagellar rotation, mediated by the DegSU system.
• The identified mechanism is conserved in *Bacillus subtilis*.

Conclusions:

• Flagella function as mechanosensors, detecting surface contact and triggering flagellar gene transcription.
• The DegSU two-component system is essential for sensing flagellar rotation restriction and inducing motility genes in *Paenibacillus* sp.
• This surface sensing and transcriptional regulation mechanism is conserved across related Gram-positive bacteria.