During the past couple months I've been thinking and writing a lot about space colonies for some reason, and I recently had the pleasure of talking with a group of iGEM students that spent last summer designing synthetic microbes that would help astronauts build a community on Mars. The Brown-Stanford joint team worked with NASA scientists on a two-pronged project. Their first project, REGObricks, uses bacteria to break down urea into chemicals that can be used to form crystals that can bond Martian sand into a strong building material. The second project is PowerCell--engineering photosynthetic bacteria that can convert sunlight into the chemical energy (like sugar) needed to power other living things. Their short teaser video is a great introduction to their team:
The team worked hard over the summer to design and build proof-of-concept systems, and ended up as a finalist in the Americas regional competition and the winner of the Best New Application prize at the International Jamboree at MIT. The following is a slightly condensed and edited version of an email conversation I had with the team and their advisor, Lynn Rothschild.
Your team brings together students and faculty from many different institutions, can you tell us a little bit about how the team got started and what it's like to be a multi-institution (and potentially multi-planet!) research project?
Brown's 2011 iGEM team was excited about the possibility of doing a NASA-related project and potentially spending last August at NASA. When it was discovered that Prof Wessel, who had previously advised the Brown iGEM team, had decided not to continue, Dr. Lynn Rothschild exploited her position as Professor (Adjunct) at Brown to become the faculty advisor. As Stanford, another university with a proud iGEM tradition was also not fielding a team, and as she was also teaching Astrobiology and Space Exploration at Stanford in her role as Professor (Consulting) at Stanford, she invited several of her Stanford students to join the team. Thus, team Brown-Stanford was born, with the entire team completing the actual research in Rothschild's lab at NASA Ames Research Center.
How did it go? Amazingly well. The students were all incredibly bright and proactive, and thanks to Skype and email were able to meld into a team with remarkable ease. Most remain very close, and two are still in Rothschild's lab - Jesse Palmer (Stanford) and André Burnier (Brown). There were obvious difficulties including the fact that lab research had to be done in an abbreviated time period and team bonding at a distance, but the advantage was multiple perspectives, backgrounds and off-set summer vacations.
NASA Ames Research Center has a new initiative in synthetic biology to investigate, promote and demonstrate the potential of synthetic biology in accomplishing NASA’s missions with a focus on astrobiology (origin and evolution of life) and the human exploration of the moon, Mars and asteroids. The Brown-Stanford iGEM team literally had the opportunity to do research which was, as described at the iGEM championship, “out of this world.”
Your projects tackle many different challenges for long-term space travel. How do you see synthetic biology being used by NASA, both in the short term and in the long term?
The initial interest has been in synthetic biology in support of human space colonization as it has the potential for greatly reduced upmass [the amount of stuff that we would need to transfer from Earth to space]. However, applications run from robotic biomining missions to earth science and astrobiology. NASA's Astrobiology Program under the name "Exobiology" has funded much of the US research in the origin of life and extremophiles for the last 50 plus years, something that we feel firmly can be an enormous asset to synthetic biology.
For the PowerCell project in particular, synthetic biology is used to help provide a source of energy in space. Even biological tools will need a source of energy. The idea behind Powercell was to provide a generalized source of energy for any other biological tools we sent to space--a "wall socket" that could be plugged into by any biotool without much hassle. We eventually wanted Powercell to provide the two most important nutrients for life - carbon and nitrogen - but we decided that the nitrogen issue was too much too deal with in one summer so we just focused on sucrose secretion. That being said, we decided to develop our system on a platform (Anabaena) that can naturally fix nitrogen so that this avenue could be developed in the future.
A big challenge for iGEM teams is just how short the summer is, making it hard to bring a project to completion. Your team had an extra constraint of not being able to actually test your designs on Mars! How did you design your experiments on Earth to show a "proof of concept" for the way things might work in space?
We had three objectives for REGObricks:
1) Proof of concept for biocementation's ability to "fuse" extraterrestrial regolith
2) Designing DNA sequence to express the urease gene clusters responsible for the biocementation function in E. coli
3) Test the hardiness of the biocementation process exposed to extraterrestrial conditions
1) We measured Sporosarcina pasteurii's native biocementation ability in several ways, including a conductivity test (the hydrolysis of urea into carbon dioxide and ammonia led to the formation of positively charged ammounium ions), a mini-biocementation process on a microslide coverslip, and a full sized 20 mL sand column. The sand column was the most challenging, as we had to design and construct a flow chamber as well.
2) We built a segment of DNA encoding for the urease gene from Sporosarcina pasteurii and transformed E. coli with it. Subsequent plating of the cells on urease test plates (agar plates containing urea and phenol red--a pH indicator that turns pink in the presence of basic pH, like ammonia) showed that the colonies did in fact possess ureolytic ability.
3) Being poor college students, we did not have a NASA budget, so we approximated with the next best thing. Teaming up with a skilled balloonist, we flew a stratospheric balloon containing our S. pasteurii bacteria and sample "regobricks" 100,000 ft into the air, where environmental stresses (uv bombardment, temperature, pressure) were analogous to Martian conditions. Upon retrieval of the samples, we plated the bacteria again on agar plates, and discovered that they were still able to hydrolyze urea, suggesting their hardiness. Due to the time crunch, we were not able to get FDA approval for releasing modified organisms into the wild, and so could not fly our transformed E. coli samples.
Here is a short video of the balloon process:
This was tough--especially since it took several weeks just to grow up our Anabaena culture, and the transformation into Anabaena is notoriously hard because of several defensive restriction enzymes not present in E. coli.
First some background: Anabaena is a filamentous cyanobacteria. It forms two cell types which separate nitrogen fixation and photosynthesis, then share the nutrients up and down the chain. We wanted to engineer our sucrose secretion device to only be on in the photosynthetic cells (because the nitrogen fixing ones aren't generating any sucrose so we don't want them to secrete what little they have!).
To this effect we were able to attach a photosynthetic-specific promoter to our sucrose secretion construct so that secretion would only be on in the photosynthetic cells. We also attached a GFP reporter to this promoter so we could verify it was working correctly (on in photosynthetic cells, off in nitrogen fixing cells - you can tell which are which by morphology). At the end of the summer, we were able to verify that our construct was regulated correctly in the different cell types by observing that in our transformed strain, the photosynthetic cells fluoresced but the nitrogen fixing ones did not. The next step was to measure sucrose secretion levels, but we did not have a good enough assay or dense enough batches of transformed Anabaena to do so at the time.
I recently saw an interesting article about astronauts producing whiskey on the International Space Station. How do you see microbes being involved in the production of food and drink in the future, in space and on earth?
Food is going to be super important for any settlement or extended exploratory mission! Since food is primarily biological, biological tools are perfectly suited to produce it. Microbes are nice because they are less delicate than plants, and you can revive whole colonies with just a few survivors.
In addition, one thing we found really interesting in talking to NASA researchers involved in the other end of the process (water reclamation) aboard space stations was that urea was usually isolated as a byproduct, stored and generally disposed of without further use. REGObricks use of urea would actually tap into this great source of organic waste that would otherwise be unused.
Your project focuses on Mars, but what applications do you think could come out of your research for Earthly technology?
Research at NASA has had a long history of spin-off technologies for terrestrial applications. REGOBricks have a lot of potential for use on Earth. A little research into the environmental consequences of traditional cement creation offers some depressing news. Ordinary Portland Cement (OPC) the most common type of cement used, is created by heating calcium carbonate (CaCO3) to extremely high temperatures (1400 C)) to create CaO, and releases CO2. The CaO is mixed with other ground up materials: clay, gypsum, to produce the OPC powder.
In total, the cement manufacturing infrastructure releases 5% of man-made CO2 emissions, half of which is generated from the breakdown of calcium carbonate and the other half is generated from the fuel combustion used to generate the high temperatures required. The amount of CO2 emitted by the cement industry is nearly 900 kg of CO2 for every 1000 kg of cement produced.
Thinking about the macroeconomic trends--globalization + urbanization means that developing countries will have an increasing demand for concrete to create industrial and civil infrastructure. If they follow developed countries footsteps in creating cement, climate conditions on the earth are in for some nasty aftereffects. On the flip side, if international regulatory bodies were to pass laws limiting CO2 generation, developing countries might further suffer a handicap in speed of development.
Biocementation allows for the creation of reasonably strong infrastructure (researchers in Murdoch university, Australia, have shown that a 7 day continuous cementation process can create a column capable of withstanding 30 Mpa of compression, equivalent to that of limestone) while bypassing traditional barriers to entry. The only challenge is the generation of ammonium ions as a result of the process, but there is active interest from fertilizer companies to see if one could collect and recycle use of this ammonium.
For the PowerCell project, the technology is equally if not more applicable in an earthly context. My personal dream is that everyone could have their own bioreactor in their backyard that could produce useful things - and operate solely off of air and sunlight! This could revolutionize manufacturing - no more need to ship materials from disperate places - just make them yourself! A much more sustainable / self-sufficient society.
What do you see as some of the biggest challenges and concerns with engineering microbes for travel to space, in terms of technical feasibility as well as the "human practices" aspects of your work?
Technical feasibility has the usual issues of genetic stability and long term storage, but the additional problems of storage in space with a potential for periodic radiation exposure, low gravity (microgravity en route, one-third Earth gravity on Mars) and a cold ambient environment. Jesse Palmer is currently working on addressing some of these issues and the 2012 team is likely to as well from a different approach. As far as "human practices" the issues become one of planetary protection. The US and other signatories of the COSPAR agreements, are very concerned about this issue, and thus NASA has a planetary protection officer, currently Dr. Cassie Conley. The concern is less one of harming the astronauts but rather one of either contaminating Mars when there could be a indigenous biotic that we would destroy or not be able to recognize (forward contamination), or bringing back organisms that are from Mars or altered during the journey (back contamination).
Also, space exploration is dangerous! You need really, really, reliable tools. Biology (and this includes bio-tools) is notorious for having its own agenda. It might be hard to keep your tools doing what you want when you want. After all, E. coli doesn't really care about space exploration :(
Anything else you want to share?
While the 2011 team focused on human settlement, stay tuned for a surprise in 2012!
Are you part of an iGEM team? Want to do a Q&A about your research? Get in touch!