Life at Interfaces: Biocomplexity in Extreme Environments

Biofilms are ubiquitous and can be found on various substrata where they can be problematic in environmental, industrial, and clinical settings. Biofilms show a remarkable resistance to biocides and antibiotics as compared to planktonic organisms. It is hypothesized that such resistance is related to the spatial structures of biofilms, which are influenced by many environmental factors.

The goal of this research is to help the biologists to pin down some key factors that determine the spatial heterogeneity of biofilms, to quantify the roles of these factors in the formation and antibiotic resistance of the biofilms, and to make predictions. To accomplish this, mathematical models were developed that describe the spatial heterogeneity and the formation mechanisms of biofilms. This is done by combining biological principles, mathematical tools and computer simulations. By comparing the results from model simulation with those from real experiments, we are able to determine what assumptions are non-realistic, what are more likely to be true, and then make predictions.

The biofilm model simulates the depletion of nutrients and electron acceptors (including oxygen), and uses principles of cell physiology to predict energy yields from different kinds of metabolic processes (e.g., respiration or fermentation) that occur in different regions of the biofilm. By taking into account differences in the allocation of energy to cell growth, stress response and maintenance, the model can be used to simulate the growth and development of multi-species biofilms that exhibit features such as patchiness, stratification into aerobic and anaerobic regions, surface roughness, and self-regulation of thickness.