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From 2010.igem.org

• Achievements • Part Design • Lab Work • Beads • Safety • Future Work •

Contents 1 Improvements 1.1 Improving the system 1.1.1 Adding further promoters 1.1.2 Increasing Signal Strength and Differences 1.2 Improving the beads 1.2.1 Adding a Coating 1.2.2 Adding Nutrient Medium

Improvements

We’re extremely proud of what we’ve accomplished this year on the wetlab side; first building and well characterising our biobrick, but then also developing our novel bead approach to improving signal detection. However the project is still far from perfect, below are several things we would like to implement were we to take the project further.

Improving the system

Adding further promoters

The most obvious extension to the project is to add the ability to detect multiple nutrients. In terms of improving fertiliser use, it would make most sense to add phosphate and potassium detection, as together with nitrogen these make up the major components of fertiliser.

There are already promoters available in the parts registry that sense Phosphate (BBa_K116401 submitted by NYMU-Taipei).

What’s more, the wide variety of fluorescent proteins available in the parts registry makes it easy to add another signal, without requiring different detection technology. These additional signals would also be compatible with our ratio method of calibrating signals.

Increasing Signal Strength and Differences

As is clear from our results, we were able both to detect our signals, and to distinguish differences between Nitrate levels quite precisely.

However, our end goal would be a signal system that could be detected by low tech equipment on farmers fields. In this case, having a stronger signal is always better. Increasing the number of bacteria in beads, as listed below, would probably help this, but so too would increasing the amount of GFP produced by our bacteria or even how bright this GFP is. Whilst this was beyond the scope of our project in the time frame, we would hope further work, ideally with collaboration from other teams would make it achievable.

Improving the beads

Adding a Coating

One of the major public perception problems highlighted by our human aspects work was fear surrounding spreading 'E. coli' in soil. Whilst our bacteria are already relatively well contained within the beads, this could be improved further by the addition of some kind of coating.

We think a cellulose coating would be an ideal candidate as it fulfils the main criteria; hopefully allowing Nitrates to diffuse in, but preventing bacteria leaving the bead. It would also be biodegradable along with the rest of the bead, reducing environmental impact.

Adding Nutrient Medium

Whilst our beads dramatically increase 'E. coli' survival and thus signal strength, we suspect this could be improved further by the addition of nutrient medium into the beads. This could even be linked to nutrient dependence - for example tryptophan auxotrophy - rendering the 'E. coli' unable to survive at all outside of the beads. This would not only increase the signal strength and thus efficiency of our product, but also make it more palatable to the public.

Regretfully we didn't have time to experiment in the lab, however, we suspect beads with nutrient media could be made by slurrying cells in Lennox Broth rather than water in the slurry stage of our bead construction procedure.