Bacterial Biofilms as a Complex Community Tracy K. Teal D. K. Newman and B. J. Wold Labs Complexity Club August 13, 2003

What is complexity? What is a good quantitative measure of complexity? No theoretical discussion of complexity. Introduction to biofilms Complexity in biology, such as functional, structural and hierarchical complexity and some of the implications of complexity in adaptation. Complexity

What is a biofilm? Bacteria that are attached to a surface and form a 3-dimensional structure, held together by an extracellular polymeric substance

Biofilms in the environment Contact lens Morning Glory Pool in Yellowstone National Park National Park Service Catheter

Biofilm formation and growth Quorum sensing and chemical signaling Microcolonies with extracellular matrix Network of channels Cells experience different environmental conditions Multi-species O2O2

Given the heterogeneity of the environment, how is the biofilm community structured? There is a strong relationship between the cell’s environment and its physiology and structure. Science News Biofilms formNutrient levels decrease towards the center Variety of environmental niches form Biofilm formation and growth

Relationship between biofilm morphology and the environment 50 um 1:10 LB 5mM lactate.5mM lactate

How are biofilms differentiated? O2O2 Given the existence of many micro- environments, how is the biofilm organized with respect to metabolism?

Shewanella oneidensis strain MR-1 –facultative anaerobe –versatile respiration –gram negative –MR-1 genome is sequenced and can be manipulated genetically

Promoter regions Unstable fluorescent proteins Microscopy Design concept Use reporter systems consisting of promoter regions fused to fluorescent proteins to indicate regions of differing metabolism within a biofilm Use oxygen respiration as indicators of the cells metabolic state O2O2

What is complexity? “Structural” complexity: Number of different parts and their interactions “Hierarchical” complexity: Number of levels in a hierarchy “Functional” complexity: –Number of different functions an organism can perform, or –Computational capacity of an organism (or device), the maximal mutual entropy between input signals and output actions. “Sequence” complexity Dr. Adami – Complexity Club, Jan 21, 2003

How is a biofilm complex? Complex cell-cell interactions Effects of environmental conditions on biofilm morphology and physiology. Multiple parameters exist and their effects are difficult to predict. More “complex” than planktonic cells Microenvironment (chemical signals, nutrient conditions) -> complex regulatory networks -> change in physiology or metabolism -> affects environment

Who cares? How is it useful? How might thinking about complexity in biofilms systems be useful? Adaptation and complexity Does the complexity of the system allow it to be more adaptable or resilient? Are there complexity measures that could allow us to predict how resilient a biofilm would be? Would decreasing the complexity of a biofilm cause it to be more susceptible to environmental influences? Important to keep in mind when working with biofilm systems