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BP: Fachverband Biologische Physik

BP 9: Focus: Systems Biology of Bacteria (with jDPG)

BP 9.6: Vortrag

Dienstag, 27. März 2012, 11:45–12:00, E 020

A model for sigma factor competition in bacterial cells — •Marco Mauri and Stefan Klumpp — Max Planck Institute of Colloids and Interfaces, Potsdam, Germany

Bacteria respond to changing environment conditions by switching the global pattern of transcribed genes, making only those products essential for their survival. In response to specif environmental stresses the cell activates several stress-specific molecules called sigma factors. They bind the core RNA polymerase (RNAP) - the machinery of transcription - and direct it towards the appropriate stress response genes. Since more than one sigma species could be present in the cell at the same time, it is believed that the modulation of their availability and competition among them for core RNAP provide important mechanisms for the global switch of the transcriptional program.

To analyze this competition, we have developed a theoretical model based on earlier work from the Gross lab [1]. The model shows that competition occurs only when the number of free sigmas exceeds the number of free cores. Within this framework, we analyzed the effects of some factors that modulate the competition such as anti-sigma factors, small RNA and active transcription. We applied the model to in vitro sigma competition experiments [2] and obtained good agreement. We also used the model to examine under which conditions a stop of transcription of ribosomal RNA as in the stringent response can passively up-regulate transcription driven by alternative sigmas.

[1] Grigorova et al., PNAS. 103, 5332 (2006)

[2] Jishage et al., Genes & Dev. 16, 1260 (2002)