Strain-dependent motility defects and suppression by a flhO mutation for B. subtilis bactofilins

Area of Science:

• Microbiology
• Bacterial Cell Biology
• Molecular Genetics

Background:

• Bactofilins are protein polymers crucial for bacterial cell shape, chromosome segregation, and motility.
• Bacillus subtilis bactofilins BacE and BacF are implicated in swimming motility, with prior studies suggesting lethality of single gene deletions.

Purpose of the Study:

• To investigate the role of Bacillus subtilis bactofilins (BacE and BacF) in bacterial motility and biofilm formation across different strains.
• To explore the genetic basis of motility defects and identify suppressor mutations related to bactofilin function.

Main Methods:

• Generation and analysis of single and double gene deletions (bacE, bacF) in Bacillus subtilis strains PY79, 168, and 3610.
• Assessment of bacterial swimming motility and biofilm formation.
• Genetic mapping of spontaneous suppressor mutations in the flagellar gene flhO.

Main Results:

• Motility defects associated with bactofilin gene deletions varied significantly among B. subtilis strains (PY79, 168, 3610).
• Gene deletions negatively impacted biofilm formation in the natural isolate 3610, indicating an additional function for BacE and BacF.
• A suppressor mutation in the flagellar gene flhO was identified, featuring an 18 amino acid C-terminal extension, linking bactofilins to flagellar regulation.

Conclusions:

• Bactofilin gene deletions exhibit strain-dependent effects on bacterial motility.
• BacE and BacF play a role in biofilm formation in B. subtilis 3610.
• Findings support a connection between bactofilins and flagellar-mediated motility, potentially operating in a switch-like mechanism.