As mentioned in Part 1 of this series, we were able to talk to a handful of the iGEM (International Genetically Engineered Machine) teams during their poster presentations last Saturday evening. Here’s the (slightly) distilled version of what we found.
The locals: Both Harvard and MIT sent teams to hold home field advantage for this year’s competition, and both took on an additional challenge right out of the gate. Generally, iGEM teams use either E.coli or brewer’s yeast, Saccharomyces cerevisiae, because they are commonly studied and react predictably in the lab. However, the locals decided to eschew this common practice and work with other critters because of what they needed their bugs to do. This required an additional time investment as the teams needed to shake up their lab procedures before starting their experiments.
The details on local and not-so-local teams after the jump!
The team from Harvard attempted to create a microbial fuel cell biosensor—that is, a system that uses bacteria to respond to changes in their environment by creating an electrical current. Their project, called BACTRICITY (which included rather adorable-looking shirts and website design), used a species already known for its electrical properties, Shewanella oneidensis, playfully referred to as “Shewie.”
The most intriguing aspect of the project was the coupling of Shewie to the extensively “customizable” E.coli in order to produce the electrical output. This system worked precisely as the team predicted. In their conclusion, they suggest possible ways to combine their project with toxin-sensing E.coli developed elsewhere in order to create the biosensor. An increase in specific toxins, like arsenic or mercury, would set off the E.coli, which in turn would cause Shewie to produce an electrical current that would be picked up by a computer. This system would rapidly detect these toxins in the water supply.
The other locals, iGEM hosts MIT, attempted to create tooth decay-fighting yogurt using the bacteria already present in yogurt. (Are you getting a sense of the creativity of these teams?) First, let’s back up and take a look at the process of tooth decay: decay-causing bugs called Streptococcus mutans attach themselves to the surface of the tooth at specific sites. However, a mini-protein, p1025, has been shown to block these sites, preventing the Streptococcus from grabbing a foothold, so to speak, on the tooth surface.
The goal of the MIT team was to use Lactobacillus bulgaricus to continuously produce p1025 so that eating the yogurt would ensure that your teeth remained cavity-free. (They note that p1025 could simply be added as a nutrient to the yogurt itself, but that using bacteria to do it means that a small portion of each “enhanced” batch could seed new ones; the Lactobacillus would reproduce and within a short time start producing more p1025 in a fresh set of yogurt.) Unfortunately, they didn’t actually make the yogurt itself, but the team was able to insert the p1025-producing gene into their bugs. With a little work it should be possible to make enriched yogurt using bacteria to secrete any nutrient you want; the possibilities are literally endless.
Reviewer’s Tilt: We talked to quite a few teams over the course of the evening, but for time and space reasons, we won’t be able to describe all of them. So as far as the out-of-towners go, there were two teams who were so friendly and helpful that it would be a shame not to thank them here and give their work some credit as well.
Just across the pond…er, the Great Lakes…were the Canadian crusaders from the University of Ottawa. They realized that in many of the iGEM projects (as well as other work) that involve continuous expression of an unnatural protein, the cells essentially wear themselves out, and through natural selection, they’ll eventually start to lose out to their more conventional counterparts over time, who don’t have the extra exertion of producing whatever it is we’re wanting them to make. (Even single-celled organisms are lazy!)
So the UOttawa kids managed to construct a system by which yeast could release a protein of interest in pulses, rather than continuously. Basically, they would turn protein production on through an external factor, but this would also produce repressors that would shut the system down very quickly. Over time, the repressors would dissipate, and the whole setup would return to its original state, ready for another burst. Think of it as having to run a long distance using a series of sprints with time to rest in between, instead of trying to sprint an entire marathon.
Across the pond for real were the delightful kids from Newcastle University. Already pseudo-celebrities in England if their jovial British boasting was to be believed, they also get bonus points for a great shirt design. Another one of the teams that chose to use an “oddball” microorganism—though apparently other labs at Newcastle specialize in working with Bacillus subtilis—their project was similar in some ways to that presented by the Harvard team.
It was also a biosensor, but instead of being sensitive to chemical toxins, Newcastle chose to use their bacteria to detect proteins produced by specific pathogens. When such proteins were detected, their “BugBusters” would respond by becoming fluorescent, and software the team wrote for this purpose (the only entirely completed portion of the project) would analyze the color pattern to figure out what had triggered the system. This sort of bacterial alarm system may become more and more prevalent in the future.
It is pretty incredible what groups of novices can think up and start to assemble in a very limited amount of time! In tomorrow's conclusion we’ll discuss the grand prize-winning project from Slovenia and see what lies ahead for synthetic biology.
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