CBE Biofilm Research Area:

Biofilm Mechanics

Biofilms are difficult to define because of their diversity, both in terms of the microorganisms that inhabit them and the environments that they are found in.  The Biofilm Mechanics Research Group uses this working definition of biofilms.

Microbial biofilms are populations of microorganisms that are concentrated at  an interface (usually solid/liquid) and typically surrounded by an extracellular polymeric slime matrix.  Whereas, flocs are suspended aggregates of micro-organisms surrounded by an extracellular polymeric slime matrix that formed in liquid suspension. They have many of the same characteristics as biofilms.

The research in our lab focuses on fundamental aspects which control the structure and dynamic behavior of bacterial biofilms, using an interdisciplinary approach drawn from microbiology and engineering. We have developed various in vitro flow cell models which

we combine with confocal and digital time-lapse microscopy to determine the growth and detachment behavior of pure culture, defined mixed culture, and environmental biofilms under various hydrodynamic and nutrient conditions. We are also currently using a non-destructive in situ technique, developed in the lab, to study the fundamental aspects of biofilm rheology (deformation and flow). This may help us understand how the interaction between a flowing liquid and the viscoelastic biofilms may result in detachment and the potential dissemination of infection and transmission of pathogens. 

By finding out about the material properties of biofilm, we can better understand how it may react when subjected to physical forces. This understanding may help us design more effective mechanical disruption methods to prevent biofilm growth. For example, when trying to remove a solid, hard, brittle material we may use a hammer and chisel. But if we are trying to get rid of a fluid, viscous material such as water, we may be able to remove it by pushing it and creating flow with a floor squeegee. All materials have certain properties of elastic solids and viscous fluids. In many of these materials, one of these properties dominates the other so that materials such as brick, steel, wood etc fall into the solids category with little evidence of any fluid-like behaviour. While materials such as water, air, and oil, clearly behave more like fluids at room temperatures. Other materials may have more equal components of both solids and fluids. Silly putty, for example, can shatter if pulled apart sharply but will flow out in a fine string if the force is applied slowly and evenly. If pushed or prodded Jello will spring back, showing elasticity but with time it softens and flows like a fluid. Biofilms appear to fall into this viscoelastic category and show aspects of both solids and liquids much like slug slime. However, as biofilms collect sediment, or become scaled with rust or calcium deposits they will become less fluid and more like a brittle solid.

Collaborators

In addition to collaborating within the CBE, we are also collaborating with other Montana State University researchers.  Aleksandra Vinogradov, Professor Mechanical Engineering, is director of the Advanced Materials Laboratory and we are developing protocols for testing biofilms grown on rheometer plates using a TA Instruments AR1000 Rheometer.  
See Rheometer

Isaac Klapper, Associate Professor of Mathematics. Isaac is bringing his expertise in applied mathematics, fluid dynamics, and solar physics to help explain the fundamental nature of biofilm as a material. Isaac is also developing a constitutive model for biofilm mechanics which may be able to predict when biofilm will detach or flow when subjected to elevated fluid shear stresses.