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Purple non-sulfur photosynthetic bacteria (PNSB) are metabolically versatile organisms that belong to the alpha-proteobacteria. This microorganisms are able to grow under a wide variety of environmental conditions, this is possible due to their sophisticated regulatory systems which coordinate metabolic changes. Our project aims to build two genetic control systems based on R. sphaeroides photosynthesis regulation (1).

The first one is the oxygen dependent system PrrBCA. It activates gene expression when the oxygen is low (2). The second is the light/oxygen mediated system that strongly 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 characterize these regulatory circuits we aim to exploit R. palustris’ metabolic versatility, and use it as a microbial factory, that could work for the production economic valuable products using CO2 as carbon source.

We are planning to use the S04147 (University of Alberta iGEM Team 2007) to evaluate butanol production controlled by our systems. This would provide an interesting way to produce this biofuel using photosynthesis under anaerobic 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.