Team/CINVESTAV-IPN-UNAM MX/oxigenresponse.htm

As we can see, in figure 1A the PpsR promoter system, in R. sphaeroides, shows a high signal (17.66%) of GFP expression, it implies that constitutive proteins from this bacteria were able to activate our system. The growth conditions were aerobic/darkness, although oxidized PpsR binds its target promoter, it is known that AppA can avoid the binding affinity of PpsR in the dark probably by the interference of an AppA-(PpsR)2 complex (Kim, 2006). In the case of AppA/PpsR complete system, we have a high GFP expression due to activity of the extra AppA and PpsR enzymes that were introduced.

The blue columns show the low GFP expression with both PrrA promoter and PrrA/PrrB complete system; in aerobic conditions PrrB autophosphorylates and passes a phosphate group to PrrA, this activated PrrA binds to its promoter region as a transcriptional repressor (Bauer, 2003).  All the results show an equivalent result with the images that were obtained by fluorescence microscope.

Figure 2A shows that in R. sphaeroides, the AppA/PpsR system promoted the GFP expression, it is possible because reduced PpsR is unable to bind its promoter and AppA is a flavin with a photoreceptor, thus under light, AppA is unable to forma a complex with PpsR and we can see GFP expression in the bacterial population.