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The purple non-sulfur photosynthetic bacteria (PNSB) belong to the alpha-proteobacteria, because of their genetic regulatory systems which coordinate different metabolic states, this microorganism are able to grow under a wide variety of environmental conditions (1).

Specifically, our project aims to build two genetic control systems based on R. sphaeroides photosynthesis cluster regulation. The first one is the oxygen dependant system PrrA/PrrB, when oxygen tension is high it remains inactive, and when the oxygen is low it activates gene expression (2). The second system is the light and oxygen mediated system AppA/PpsR that represses gene expression under aerobic conditions and allows transcription in the absence of oxygen and light (3).

To achieve this goal we designed a genetic circuit in which GFP expression is oxygen and light-dependent by the antirepression of PpsR and oxygen dependent by the activation of PrrA/B system. The lab work is accompanied by a computational model, which will provide a way of testing our knowledge of these systems.

Once, we have characterized the functionality of these regulatory circuits we aim to take advantage of R. palustris’ metabolic versatility, and use this bacteria as a microbial factory, that could work for the production of metabolites with economic value products using as carbon source such as CO2.

We are planning to use the S04147 clostridial butanol production operon (University of Alberta iGEM Team 2007) to evaluate the synthesis of this biofuel, linking it to our control systems. This would provide an interesting way to produce butanol using CO2 as carbon source under anaerobic photosynthetic conditions.

Figure: General Scheme of the project

Figure: General Scheme of the project

  1. 1.Hunter CN, Daldal F, Thurnauer MC, Beatty JT: (2009) The Purple Phototrophic Bacteria. Springer; 200928. pp. 707–725.
  2. 2.Elsen S, Swem LR, Swem DL, Bauer CE. (2004). RegB/RegA, a highly conserved redoxresponding global two-component regulatory system. Microbiol. Mol. Biol. Rev. 68:263–79.
  3. 3.Shinji Masuda2 and Carl E. Bauer (2002)  AppA Is a Blue Light Photoreceptor that Antirepresses Photosynthesis Gene Expression in Rhodobacter sphaeroides Cell, Vol. 110, 613–623, September 6, 2002.