Slide 1
Modeling Nisin-Induced Bacterial FluorescenceKey properties of
the systemCertain types of bacteria are sensitive to nisin
(peptide)High levels of nisin induce cell deathWe can engineer the
bacteria to fluoresce (produce GFP) for intermediate levels of
nisin1
Nisin sourceModeling Nisin-Induced Bacterial
FluorescenceExperimental setupWe can grow a population of nisin
sensitive bacteria in a petri dishWe then place a chemical mask
(high nisin concenration) on top of the cell layerThe nisin
diffuses down to the cells and causes fluorescence2
Modeling Nisin-Induced Bacterial FluorescenceModeling diffusion
on a computerDiffusionMolecules are in constant motion, and they
move in all directionsThe constant motion tends to eliminate areas
of high/low concentration (think about how you can smell someone
cooking in a different room gas molecules can diffuse freely
throughout your house)Computer ModelWe can model diffusion on a
computer by simulating the movement of each moleculeWe model space
as a grid of pointsEach molecule can move to an adjacent point at
each time step with an equal probabilityWe also incorporate the
degradation of molecules by decreasing the total number at each
time step
3Modeling Nisin-Induced Bacterial FluorescenceModeling
fluorescence on a computerWe model our petri dish and cell layer as
a 3-dimensional gridThe top layer of the dish has a high initial
nisin concentration in some specific shapeWe then simulate
diffusion of the nisin down to the cell layerThe cell layer then
fluoresces for a certain amount of nisin reaching the bottom
layerIf the nisin concentration is above a certain threshold value,
the cells do not fluoresce (because of cell death)If the nisin
concentration is below a certain threshold value, the cells are not
stimulated to fluoresce4Modeling Nisin-Induced Bacterial
Fluorescence5
DiffusionTop View Initial SetupIndicator Layer