In the past few years astronomy and aerospace engineering have been reaching incredible goals by leaps and bounds: ESA’s first comet landing on 67P/CG comet (ESA, 2016) and NASA’s New Horizons spacecraft historic flyby of Pluto (NASA, 2015a) to list some. Nowadays interplanetary missions with a crew on board, especially to Mars, are not science fiction anymore. Many space agencies, both public and private, have worked out a lot of the logistics and put some early dates for future long-term space travels. In this scenario a call for synthetic biology and biotechnology is essential to ensure a successful trip and stay on other worlds.
Definition of the problem
Space missions face the problems that transporting mass is expensive and the needs of long expeditions are unknown in advance. All space travels are in fact subjected to stringent restrictions on the mass and volume of equipment (Scienceogram, 2015; Wall M, 2015). It would be revolutionary to have the capacity to manufacture various resources needed without prior knowledge of exact mission requirements.
How did we do it?
We have designed a modular co-culture system to accomplish this: containing the cyanobacterium Synechococcus elongatus to use CO2 and light, which are plentiful on Mars, to produce sucrose. This is used as a common feedstock by Bacillus subtilis to generate essential end-products (Jung et. al., 2009). We focused on polylactic acid P(LA-co-3HB) as a proof-of-concept, since 3D printers can use it for tools and machine parts (Yamada et. al., 2010). Long-term expeditions would benefit enormously from onboard manufacturing capabilities.
Figure 1: Figure of our principle
Principle of the bioreactor. An inner compartment made from a repurposed dialysis bag (2 kDa, Spectra/Por ® 6 dialysis membrane, 132633) contains Bacillus producing a product. The outer compartment contain Synechococcus secreting producing a carbon source for bacillus to live on. The dialysis bag serves both as mechanical separation and easy extraction of the product without cross contamination. Edited and reprinted with permission of Gert Gram and Jyllands-Posten.
We decided to expand on a former project in iGEM, to further develop on a great idea, but at the same time to put principles into practice that had not been done before. The usage of cscB transformed S. elongatus as a sucrose provider was inspired from the work of Brown-Stanford iGEM 2011 and Daniel Ducat at Pamela Silver’s Lab (Ducat et. al., 2012). Those studies give us the hint of the characterization of the BioBrick Bba_K656011 already present in the registry and essential for sucrose export in our co-culture.
To examine the co-culture’s practicality in extraterrestrial environments, the cutting-edge Jens Martin Mars Chamber was used to test stresses including UV exposure and pressure extremes (Kajtár RE, 2014). We propose that Bacillus’ sporulation ability will enable missions to maintain libraries of strains, each producing a different resource from sucrose that may be useful in space exploration. This modularity will minimise the equipment needed by using a single platform, without sacrificing too much in terms of versatility.
Figure 2: The Jens Martin Mars Chamber at the Niels Bohr Institute used to test the behaviors of our bacteria under harsh conditions.
How did everything start?
The Copenhagen University iGEM 2016 team is very diverse, with specialisations ranging from biotechnology to computer science. It was important to find a project that appealed to all of these interests; the previous year’s iGEM team had conducted a wide-ranging project: SpaceMoss. We thought that a space-related project would give ample opportunity to utilise both the biotechnological skills of the group as well as the more physics-oriented ones.
SpaceMoss had inserted an antifreeze gene into moss to improve survivability on Mars, and this year’s project built on that by considering the functions transgenic organisms could fulfil in space travel and habitation. The team also desired, as part of the outreach aspect of iGEM, to take advantage of widely publicised areas of science. Miniaturised production platforms, or ‘minifacturing’, are coming to the fore with 3D printers generating more complex and varied objects. We imagined that a 3D printer on the International Space Station (NASA, 2015b) could use the bioplastic polylactic acid (PLA) to make tools and parts, it was decided to produce PLA for extra-terrestrial use.
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NASA (2015b) International space station’s 3D printer www.nasa.gov
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