Four examples from B. subtilis·Growth versus competenceSwimming versus chainingEating versus being eatenCommunity versus individuality
Four examples from B. subtilis • Growth versus competence • Swimming versus chaining • Eating versus being eaten • Community versus individuality
1. Growth versus CompetenceB. subtilis cells can enter a specialized stateof“competence" in which they take up DNAfrom their environment.Entry into competence is controlled by theregulatory protein ComK, whose synthesis isgoverned by a noise-driven stochastic switch
1. Growth versus Competence B. subtilis cells can enter a specialized state of “competence” in which they take up DNA from their environment. Entry into competence is controlled by the regulatory protein ComK, whose synthesis is governed by a noise-driven stochastic switch
Cells with GFP fused to a ComK-controlled geneOnly some cells areComK-ON
Only some cells are ComK-ON! Cells with GFP fused to a ComK-controlled gene
ComKComKD~100 genescomkExpressionofcomkisgovernedbyapositivefeedbackloopinwhichComK stimulates transcriptionfromthe promoterforitsowngene.TheloopishighlysensitivetostochasticfluctuationsinComklevels
P comK ~100 genes Expression of comK is governed by a positive feedback loop in which ComK stimulates transcription from the promoter for its own gene. The loop is highly sensitive to stochastic fluctuations in ComK levels. ComK ComK
2. Motility versus chaining
2. Motility versus chaining