Parts | Days | Selection | Search | Updates | Downloads | Help
BP: Fachverband Biologische Physik
BP 7: Posters: Statistical Physics in Biological Systems
BP 7.7: Poster
Monday, March 14, 2011, 17:15–20:00, P3
A Switch Like Response of Photosynthetic Bacteria to Changing Redox and Light Conditions — •Rakesh Pandey1, Dietrich Flockerzi1, Marcus J. B. Hauser2, and Ronny Straube1 — 1Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany — 2Institute of Experimental Physics, Otto-von-Guericke University, Magdeburg, Germany
Facultative photosynthetic bacteria switch their energy generation mechanism from respiration to photosynthesis depending on oxygen tension and light. Part of this transition is mediated by the conserved transcriptional repressor PpsR which specifically represses components of the photosynthetic apparatus under aerobic conditions. In Rhodobacter sphaeroides the repressive action of PpsR is antagonized by the redox and blue light sensitive flavoprotein AppA. At intermediate oxygen levels the interaction between AppA and PpsR leads to the repression of photosynthesis genes under high light illumination which is believed to reduce the risk of photo-oxidative stress. To elucidate the underlying mechanism for this phenotype we developed a simple mathematical model. Investigations of the steady-state behavior show that high light repression can indeed occur at intermediate oxygen levels if PpsR is reduced on a faster time scale than AppA. The model further shows that if AppA copy numbers exceed those of PpsR the low to high light transition can occur via a bistable switch which might help the bacterium to cope with changing light conditions, especially at intermediate oxygen levels.