Human Practices

Caffeinated Coli

In 2014, the UT Austin iGEM team reached out to the community by going to dozens of Austin coffee shops, located throughout the city (figure 1), and collected samples of their house coffee. We then took these samples back to our lab, and using a strain of E. coli previously developed by the 2012 UT Austin iGEM, we employed the E. coli to assess how much caffeine was present in each cup of coffee (figure 2).

A couple of weeks later, we presented this data at the 2014 South by Southwest (SXSW) festival as part of the SXSW Create section, which focuses on maker/hacker/do-it-yourself science and technology. As part of this outreach, we explained our project and synthetic biology to a wide range of people. (figure 3 - poster) Many people who came by had little to no background in science or technology, and even most of the ones who did had not heard about synthetic biology. By talking about synthetic biology with an interesting and easy to understand application, we were able to explain what it is and how useful it can be to people who may have misconceptions about what sorts of things you can do with genetics.

Measuring Caffeine Content

The E. coli we used were a modified knockout strain that could not synthesize guanine using its normal pathway, but had a plasmid introduced with a set of genes that allowed it to synthesize guanine from xanthine and many of its derivatives, including caffeine (figure 4). Without caffeine (or certain other xanthine derivatives), the strain will not grow. When caffeine is added, the strain will grow normally until it runs out of caffeine, at which point it will stop growing. Thus, by looking at the relative growth of the strain with different samples of coffee and comparing it to a standard curve of growth in solutions with known amounts of caffeine (figure 5), we could somewhat accurately measure the amount of caffeine in the coffee.

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