With all of the components of the system in place, we could begin to test for a response to PAI-1. To this end, cells containing the construct were cultured in LB medium, cultures were spiked with 500μM synthetic PAI-1 in DMSO and samples were withdrawn at time periods of up to one hour following PAI-1 addition. A western blot with anti-GFP antibodies was performed on the treated cells alongside an un-spiked, PAI-1 negative control, and MC1061 cells harbouring the empty pSB1C3 vector. The results are shown in Fig 3. As shown in Fig 3A, GFP production is activated by PAI-1 following a 60 minute induction period. Thus the LasR/plasB circuit has responded as expected to the presence of PAI-1. Fig 3B shows a high basal GFP production driven by PluxR in the absence of the auto-inducer molecule (PAI-1), however there is increased GFP production over time in the presence of PAI-1. The basal GFP production seen from PluxR in the absence of PAI-1 may reflect the fact that this is a ‘foreign’ promoter from V. fischeri and is not naturally regulated by LasB. Therefore regulation from this hybrid system might expected to be non-optimal. None-the-less these data show that both of our engineered systems respond to PAI-1.

The following parts were deposited as Biobricks