Insertion of new maxima at maximum distance from the poles
In the Gram positive rod, B. subtilis
, MinE is absent and no pole-to-pole oscillations of MinC/MinD occur. Instead, stable maxima of this division inhibitor are maintained at both poles . Under their repelling influence, the Z-ring assembles at the largest possible distance from both maxima, i.e., at the center [1-3]. Although a detailed modeling for B. subtilis
has to be worked out, the general models suggest a relatively simple mechanism that allows for center-finding in a more static system.
If pattern forming reactions are at work, new maxima are formed during growth. This can happen either by a split and shift of existing maxima, or by the trigger of new maxima in the enlarging interstices. Splitting
is the prevalent mode if the antagonistic reaction is accomplished by the depletion of a substance required for autocatalysis, and has been discussed above. In contrast, if an activator /inhibitor reaction is involved, new maxima become inserted whenever the distance to existing maxima exceeds a certain value. At these positions, the inhibitor (red) concentration becomes so low that the onset of autocatalysis can no longer be suppressed. In the first simulation, a small but growing field is assumed (equation and parameters
). Initially a polar pattern emerges. If a certain size is surpassed, a second maximum is generated at the opposite pole. The result is a symmetrical pattern: