Visualizing dynamic competence pili and DNA capture throughout the long axis of

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Genetics

Background:

• Bacterial natural transformation is a key mechanism for horizontal gene transfer.
• The initial DNA capture step is mediated by competence pili, but their structure in Bacillus subtilis remained unvisualized.
• Previous studies relied on genetic and functional data to infer pilus involvement.

Approach:

• Utilized fluorophore-conjugated maleimide labeling for visualization.
• Employed epifluorescence microscopy to observe functional competence pili in Bacillus subtilis.
• Analyzed pilus length, retractile properties, DNA association, and cell surface distribution.

Key Points:

• Functional competence pili in Bacillus subtilis were visualized for the first time.
• Pili are approximately 300nm in length, retractile, and bind to DNA.
• Pili are distributed along the cell's long axis, not just at the poles.

Conclusions:

• The findings support a distributed model for Bacillus subtilis transformation machinery.
• Initial DNA capture by pili occurs along the cell's long axis.
• Subsequent DNA processing steps may also occur away from the cell poles.