Background

Synechocystis PCC6803 as a model chassis

Cyanobacteria have been the first truly photosynthetic microorganisms to appear on earth about 2.4 billion years ago. (ref:Evolution of photosynthesis. Hohmann-Marriott MF, Blankenship RE.)With the emergence of synthetic biology and new genetic tools it is of no surprise that many research groups are using cyanobacteria as a chassis suitable for a range of aplications. They include: detection of water soluble pollutants and commodity chemicals production (reference)

Among the many qualities of synechocystis there are two of them that provided us an interesting opportunity to develop an iGEM project. First, being a photosynthetic organism, each culture is, at least for an important time span, a self sustainable system. Second, cyanobacteria are the only prokaryotic organisms to exhibit circadian behaviour. Moreover, the principal proteins involved in the process have been characterised in synechococcus as well as the cyclic expression pattern in synechocystis. (reference)

Lux operon: more than just a reporter

The lux operon is a group of genes that is responsible for a density dependent bioluminescent behavior in Vibrio Fischeri. It is composed of 8 genes, LuxA and B encode for a heterodimeric luciferase; LuxC, D and E the enzymes that recover the decanal substrate and LuxR and I are responsible for regulating the whole operon. Lastly LuxG is believed to act as a FMNH2 dependent FADH2 reductase, although luminescence is not affected in its absence. LuxAB has been widely used as a reporter dependent on the addition of tetradecanal to the cultures. In 2010 Cambridge iGEM team engineered these genes to a biobrick format making them part of the toolkit available to all iGEM teams.

As a team we decided to work with this operon for the folowing reasons, first of all, the luminescence produced by this pathway is much more visually appealing than other systems from the registry (i.e XFPs), and moreover, the light production doesn´t depends on a single peptide but on a whole pathway, wich makes it more tunable, for instance, decoupling in time the substrate recovery from the luciferase reaction itself.