Silver Ions Inhibit Bacterial Movement and Stall Flagellar Motor

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Increasing bacterial resistance to antibiotics necessitates novel antimicrobial strategies.
• Silver's antimicrobial properties are well-known, but its precise mechanisms, particularly on bacterial motility, remain unclear.
• Bacterial motility is a critical factor in virulence and infection progression.

Purpose of the Study:

• To investigate the effect of silver ions (Ag+) on the motility of Escherichia coli (E. coli).
• To elucidate the impact of Ag+ on bacterial flagellar motor function and dynamics.
• To provide a quantitative understanding of how Ag+ affects bacterial movement.

Main Methods:

• Utilized swimming, tethering, and rotation assays to observe E. coli behavior.
• Quantified changes in bacterial swimming speed and flagellar motor rotation.
• Applied hidden Markov model (HMM) analysis to tethering assay data.

Main Results:

• Ag+ ions dramatically reduced E. coli swimming speed by over 70%.
• Observed a significant 77% increase in bacterial tumbling/pausing frequency in the presence of Ag+.
• Found that Ag+ significantly decreased the tumbling/pausing-to-running transition rate by 75%, suggesting stalled flagellar motor rotation.

Conclusions:

• Ag+ ions directly inhibit bacterial motility by affecting flagellar motor function.
• The findings suggest that silver ions can stall bacterial flagellar motors, impacting bacterial movement.
• This study provides a quantitative mechanistic insight into the antimicrobial action of silver against bacterial motility.