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Basal expression rate of comK sets a ‘switching‐window’ into the K‐state of Bacillus subtilis
Author(s) -
Leisner Madeleine,
Stingl Kerstin,
Rädler Joachim O.,
Maier Berenike
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.05628.x
Subject(s) - biology , population , bacillus subtilis , basal (medicine) , microbiology and biotechnology , genetics , bacteria , endocrinology , demography , sociology , insulin
Summary Bacillus subtilis cell population divides into a competent fraction and a non‐competent fraction in the stationary phase. The transition from the non‐competent state (with basal ComK concentration) to the K‐state (with high ComK concentration) behaves like a bistable switch. To better understand the mechanism that sets the fraction of cells that switch into the K‐state (K‐fraction), we characterized the basal comK expression in individual non‐competent cells and found a large cell‐to‐cell variation. Basal expression rate increased exponentially, reached a maximum and decreased towards zero in the stationary phase. Concomitantly, the intrinsic switching rate increased and decreased with a time lag. When switching was induced prematurely by reduction of ComK proteolysis, the K‐fraction increased strongly. Our data support a model in which the average basal level of ComK raises during late exponential phase and due to noise in basal comK expression only those cells that are on the high end of comK expression trigger the autocatalytic feedback for ComK transcription. We show that a subsequent shut‐down of basal expression rate sets a ‘time‐window’ for switching and is thus involved in determining the K‐fraction in the bimodal population.