Bacterial%20Biofilms%20as%20a%20Complex%20Community

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

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What is a biofilm?
Bacteria that are attached to a surface and form
a 3-dimensional structure, held together by an
extracellular polymeric substance
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Biofilms in the environment
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Biofilm formation and growth
O2

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

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Biofilm formation and growth
Given the heterogeneity of the environment, how
is the biofilm community structured? There is a
strong relationship between the cells
environment and its physiology and structure.
Biofilms form
Nutrient levels decrease towards the center
Variety of environmental niches form
Science News
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Relationship between biofilm morphology and the
environment
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How are biofilms differentiated?
Given the existence of many micro-environments,
how is the biofilm organized with respect to
metabolism?
O2
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Shewanella oneidensis strain MR-1

• facultative anaerobe
• versatile respiration
• gram negative
• MR-1 genome is sequenced and can be manipulated
  genetically

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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

• Promoter regions
• Unstable fluorescent proteins
• Microscopy

O2
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What is complexity?
Dr. Adami Complexity Club, Jan 21, 2003

• 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

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How is a biofilm complex?
Microenvironment (chemical signals, nutrient
conditions) -gt complex regulatory networks -gt
change in physiology or metabolism -gt affects
environment

• 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

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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