Bacterial Biofilms as a Complex Community

Tracy K. TealD. K. Newman and B. J. Wold LabsComplexity 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

O2

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 form Nutrient 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 LB5mM lactate.5mM lactate

How are biofilms differentiated?

O2

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

O2

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