IGEM:IMPERIAL/2007/Projects/Biofilm Detector/Notes

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Infector Detector: Notes

Making Biofilm

  • Freshly-grown growth-phase E. coli ZK1056 culture is added to sterile medium to a concentration of 5 × 107 cells/mL.
  • Round 15 mm sterile glass coverslips are placed upright in the wells of a 24-well plate with sterile plastic stands
  • Add 1 mL of E. coli solution to each well.
  • The 24-well plate is immediately covered and transferred to a 30 °C incubator.

AHL produced in biofilms:

(Notes on the journal modeling AHL production in biofilms of the same bacterial population) AHL synthesis is subject to autoinduction in which production of AHLs operates as a positive feedback loop.
Assumptions made in the model:

  • All bacterial cells are physiologically identical with regard to size, shape and permeability of the cell membrane, as well as production and degradation rates of the signalling molecules
  • Bacterial population exhibit a standard logistic growth pattern
  • No metabolic or physiological lag is assumed
  • At very low Cbc, the net rate of AHL production, h(Cbc), is assumed to be determined solely by the difference between basal production, Bp, and degradation of AHLs
  • Degradation of AHLs is proportional to the concentration of AHL and occurs at a rate d*Cbc

Not considered in the model: permeability constant a, which is characteristic of the bacterial cell membrane, the diffusability of a given AHL, and the viscosity of the cell and the biofilm

Conclusions from the model: high concentrations of AHL inside cells could be achieved at very low population densities. Rapid rise in AHL concentration early in population growth, followed by a plateau, followed by another rise to a second plateau

Biofilm detection using AHL as signals