The Effects of Microgravity on Microbial Nitrogen Fixation (Microbial Nitrogen Fixation) studies two species of soil-dwelling bacteria to understand the effects of microgravity on microbial nitrogen fixation. Azotobacter vinelandii, a free living strain, and Rhizobium leguminosarum, a symbiotic strain that infects the root systems of leguminous plants are the experimental organisms. Escherichia coli (not capable of nitrogen fixation) is included as a negative control.

Nitrogen fixation is an essential process of agricultural systems and a necessary component for translating agriculture to spaceflight environments. The results of this study further our understanding of how specific strains of bacteria can aid in the successful growth of crops in space.

The experiment will launch on 2/9/2020 aboard NG-13 and will returns on 4/2/2020 aboard SpX-20. Following installation the International Space Station, it will run for 7 – 8 weeks and moved to cold storage until return on the Dragon Capsule.

Earth Application

Soil microflora are critical to converting nutrients into forms that can be absorbed and utilized by plants. The Microbial Nitrogen Fixation experiment informs our understanding of nitrogen fixation responses of selected microbes in microgravity, with potential to improve our understanding of the impact of climate change on soil productivity.

Flight Protocols

As a follow-on to Flight 6, magnitude.io/ proposes to fly cowpeas (Vigna unguiculata) and common beans (Phaseolus vulgaris) seedlings in a 4-tube 2u lab (similar to SpaceX-16 ExoLab-5 cubelab). These species of legumes , nodulate with R. leguminosarum which is readily available from Carolina Biological, additionally, they are food crops. These two species are also more heat tolerant than other leguminous food crops. By flying seedlings, we are able to select the best specimens for flight and reduce the need for cold stow & late load.

Two tubes of each plant would be used, one with standard growth media and un-inoculated seeds, the second with seeds inoculated with R. leguminosarum. Approximately L -7 to -10 days pre-launch, seeds would be “planted”. At L-3, the best seedlings will be selected and loaded into the ExoLab. By using seedlings, there will be no need to hold the experiment in stasis via cold-stow. The MET for the experiment will need to start at L-planting days to properly sync with the classroom ground control labs.

Thermal conditions continue to be a challenge for plants, therefore, if at all possible, we request Space Tango to explore heat mitigation potentials for this flight. This might include active ventilation and/or loading on the orbital rack that has the lowest temperature. If there are experiments that will be generating less heat, perhaps the ExoLab could be loaded with those experiments.

The proposed experiment will further examine the potential of sustainably cropping in space. By establishing viability of legumes and their nodulation with Rhizobium in microgravity, not only will legumes be potential food crops for human space exploration, but other crops that are nitrogen intensive to grow will have a natural source of nitrogen through the production of excess fixed nitrogen by the Rhizobial nodules of legumes. 

Flight 7 will be using existing flight hardware, thus reducing costs and eliminating design-build time requirements.

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ExoLab Mission #6 takes place in a sealed 2U CubeLab populated with eight petri dishes. Two species of nitrogen fixing bacteria are included in the investigation, each on three petri dishes. The remaining two petri dishes are inoculated with E. coli to serve as a control. The CubeLab is turned over at L-3 for cold stow to deter growth until installation on TangoLab. The experiment runs at ambient conditions in the TangoLab, and imagery and sensor data is collected on regular intervals. After experiment completion, the CubeLab is returned in cold stowage (4oC) for further ground analysis.

Students will run ground analogs to the Flight 6 experiment in two parts, first with Rhizobia, followed by Azotobacter. Each trial will consist of four petri dishes. Students will document and share observations with the ExoLab network.