Difference between revisions of "Bacillus subtilis spreads by surfing on waves of surfactant"

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(Motivation)
(Motivation)
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==Motivation==
 
==Motivation==
In times of stress ''Bacillus subtilis'' form a dense mat of exopolysacharides that allows the bacteria to bind to solid or liquid surfaces. Stress causes a subpopulation of ''B. Subtilis'' to differentiate into the so-called cannibal cells.  The cannibal cells secrete
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In times of stress ''Bacillus subtilis'' differentiate into spores, which helps them survive but at a significant energy cost. ''B. Subtilis'' try to keep this by three known mechanisms: 1) a sub-population of cells differentiations into cannibal cells, which selectively lyse non-cannibal cells; 2) the cells form a dense mat of exopolysacharides, called a biofilm; and 3) the cells spread out in search of a more hospitable environment. All three mechanisms appear to be controlled by the same regulatory protein, Spo0A. This protein is part of a quorum sensing system. The lipopetide surfactin secreted by the bacteria
 
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A key question is the nature of the mechanism by which biofilms spread. The spreading is initiated when nutrients in the environment run low, and has probably evolved to help ''B. subtilis'' find new food sources.
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==Experimental Observations==
 
==Experimental Observations==

Revision as of 15:06, 9 November 2009

currently being edited by Nikolai

Reference

Bacillus subtilis spreads by surfing on waves of surfactant

Angelini T.E., Roper M., Kolter R., Weitz D.A., Brenner M.P.

PNAS 106: 18109-18113 (2009) PMID: 19826092 (Pubget)

Motivation

In times of stress Bacillus subtilis differentiate into spores, which helps them survive but at a significant energy cost. B. Subtilis try to keep this by three known mechanisms: 1) a sub-population of cells differentiations into cannibal cells, which selectively lyse non-cannibal cells; 2) the cells form a dense mat of exopolysacharides, called a biofilm; and 3) the cells spread out in search of a more hospitable environment. All three mechanisms appear to be controlled by the same regulatory protein, Spo0A. This protein is part of a quorum sensing system. The lipopetide surfactin secreted by the bacteria

Experimental Observations

Hypothesis

Conceptual Explanation

A 'B. subtilis' biofilm is thicker in the center that at the edges. If we assumed that:

  • Surfactin secreted by cells moves quickly to the air-biofilm interface.
  • Surfactin reduces the film surface tension.
  • All cells secrete surfactin at the same rate.
  • The bacteria are homogeneously distributed throughout the film.

Scaling Analysis

Mathematical Model

References

López D, Vlamakis H, Losick R, Kolter R., Cannibalism enhances biofilm development in Bacillus subtilis. Mol Microbiol (2009). Pubget