Strengthening biofilms with selective metal ions

Area of Science:

• Microbiology
• Materials Science
• Biophysics

Background:

• Biofilms are microbial communities encased in extracellular polymeric substance (EPS).
• EPS can incorporate metal ions, potentially enhancing biofilm mechanical properties and survival.
• Quantitative mechanical properties of metal ion-influenced biofilms are poorly understood.

Purpose of the Study:

• To develop and apply a technique for characterizing the uniaxial stress-strain response of bulk bacterial biofilms exposed to metal ions.
• To investigate the impact of specific metal ions on the mechanical properties of *Bacillus subtilis* biofilms.
• To elucidate the role of EPS crosslinking in mediating the mechanical effects of metal ions.

Main Methods:

• Developed a technique to measure the uniaxial stress-strain response of bulk bacterial biofilms.
• Applied the technique to *Bacillus subtilis* pellicles exposed to various metal ions.
• Assessed the reversibility of mechanical changes using a chelating agent and evaluated pH effects.

Main Results:

• Exposure to selective metal ions significantly increased the low strain elastic modulus and maximum stress of biofilms.
• Failure strain of the biofilms was decreased upon exposure to metal ions.
• The observed mechanical changes were reversible with a chelating agent, and pH variations had minimal impact.

Conclusions:

• Metal ions enhance biofilm mechanical integrity through EPS crosslinking.
• Understanding these ion-mediated mechanical alterations is vital for developing effective biofilm mitigation strategies.
• This study provides quantitative data on biofilm mechanical properties, informing applications in biofouling and healthcare.