So far it has proven to be less growth-friendly. But the lunar soil could possibly be transformed by tiny helpers into a better substrate for plant production in the planned lunar stations, according to a study. The scientists have identified three species of soil bacteria that are particularly effective at making the nutrient phosphorus available to plants from replicas of the lunar regolith. Experiments also confirmed that the microbes significantly promote the growth of test plants in the simulated lunar soil.
After the first exploration over 50 years ago, humanity will soon gain a permanent foothold on the moon: the construction of bases on the Earth’s satellite is planned. However, this ambitious goal is associated with enormous challenges, which research teams are currently working on overcoming. A fundamental problem is the availability of resources, because transporting materials from the Earth to the Moon is complex and expensive. Therefore, the resources available locally should be used as effectively as possible. This also applies to the planned plant production, which is intended to serve the food supply, oxygen production and water treatment in the lunar stations. In order to avoid having to bring plant substrate and little fertilizer to the moon, we are currently exploring the extent to which the existing lunar soil is suitable for cultivation.
Can the alien plant substrate be improved?
Basically, growth tests in sample material from the Apollo missions have already shown that plants can thrive in the so-called lunar regolith – but rather poorly. Due to unfavorable characteristics, the lunar soil forms a comparatively poor substrate. One factor is that it contains the important plant nutrient phosphorus in a form that is not available to plants. As part of their study, researchers led by Yitong Xia from the China Agricultural University in Beijing investigated the extent to which certain terrestrial soil bacteria could contribute to solving this problem. It is known that some species can release mineral-bound phosphorus in a form that is available to plants through certain excretions. But do they also succeed in the case of the lunar regolith?
The team chose five soil bacteria species known as phosphorus mobilizers as microbial test candidates: Bacillus mucilaginosus, Bacillus megaterium, Bacillus subtilis, Bacillus licheniformis and Pseudomonas fluorescens. They were cultured in the laboratory in experimental medium, which the scientists then added with simulated lunar regolith. It is a substance that corresponds as closely as possible to the composition and consistency of the material that was collected on the moon during the Apollo missions and brought to Earth.
Phosphorus release and growth promotion
As the team reports, the research results initially showed that soil microbes can also release plant-available phosphorus in relevant quantities from the simulated lunar regolith. However, there were clear differences: Bacillus mucilaginosus, Bacillus megaterium and Pseudomonas fluorescens were best at cracking the lunar material, the analysis results showed. The scientists explain that they apparently cope better with the special material characteristics than the other two types of bacteria.
To test how these three microbes affect growth in the simulated lunar regolith, the team then carried out experiments using tobacco plants as a model. This confirmed that treating the substrate with a mixture of the living bacteria can lead to significant increases in growth compared to controls. Specifically, there was a significant increase in the content of the plant pigment chlorophyll, which is important for photosynthesis. Compared to controls growing on the substrate spiked with dead bacteria, the treated plants also developed more biomass and longer stems and roots over the course of 24 days.
The scientists come to the conclusion: “We were able to show that these bacteria can effectively improve the fertility of simulated lunar regolith, making the material a good growing medium for higher plants,” write Xia and his colleagues. According to them, there could be considerable potential for the planned lunar missions in the little helpers: the targeted use of the microbes could significantly reduce the effort required to allow lunar gardens to flourish, which provide the station’s residents with food, oxygen and treated water.
Source: Communications Biology, doi: 10.1038/s42003-023-05391-z