Paper Number
PO72 

Session
Poster Session

Title
Microrheological investigation of a biofilm and its constituent extracellular polymers

Presentation Date and Time
October 8, 2014 (Wednesday) 6:05

Track / Room
Poster Session / Poster

Authors (Click on name to view author profile)

1. Ganesan, Mahesh (University of Michigan, Chemical Engineering)
2. Younger, John G. (University of Michigan, Emergency Medicine)
3. Solomon, Michael J. (University of Michigan, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Mahesh Ganesan¹, John G. Younger², and Michael J. Solomon^1
1Chemical Engineering, University of Michigan, Ann Arbor, MI; ²Emergency Medicine, University of Michigan, Ann Arbor, MI 48109

Speaker / Presenter 
Ganesan, Mahesh

Text of Abstract
We report the creep compliance of a model biofilm formed by Staphylococcus epidermidis and its polymeric extracellular matrix (ECM) over a time range of 10^-5 – 10¹ s, as measured by diffusing wave spectroscopy (DWS). Biofilms are biological soft matter, consisting of bacterial cells embedded within a self-produced ECM. Thus, the bulk mechanical properties of a biofilm originate due to the coupled response of cells and ECM polymers. The components of this response can be probed using microrheology. Using DWS, we track the motion of thermally driven probes in re-constructed ECM and in biofilms cultured directly in rectangular glass cuvettes. We found that the short time (< 10^-3 s) creep of the biofilm was congruent with that of the reconstructed ECM up to a finite compliance of ~ 10^-2 Pa^-1. This response was that of a viscous liquid with viscosity of ~ 10^-2 Pa.s. For time > 10^-3 s, we find a transition from a purely viscous to a viscoelastic response characterized by a long time plateau in creep that agrees well with results from mechanical rheometry (L. Pavlovsky et al., Soft Matter, 9, 2013). The transition region was found to depend on the amount of biofilm growth. The biofilm creep deformation can therefore be viewed as a viscous, polymer mediated response in parallel with a cellular suspension mediated elastic response. This study identifies the particular contributions of ECM and cells to the mechanical properties of bacterial biofilms.