Soil fertility interactions with Sinorhizobium-legume symbiosis in a simulated Martian regolith; effects on nitrogen content and plant health

Abstract

Due to increasing population growth and declining arable land on Earth, astroagriculture will be vital to terraform Martian regolith for settlement. Nodulating plants and their N-fixing symbionts may play a role in increasing Martian soil fertility. On Earth, clover (Melilotus officinalis) forms a symbiotic relationship with the N-fixing bacteria Sinorhizobium meliloti; clover has been previously grown in simulated regolith yet without bacterial inoculation. In this study, we inoculated clover with S. meliloti grown in potting soil and regolith to test the hypothesis that plants grown in regolith can form the same symbiotic associations as in soils and to determine if greater plant biomass occurs in the presence of S. meliloti regardless of growth media. We also examined soil NH4 concentrations to evaluate soil augmentation properties of nodulating plants and symbionts. Greater biomass occurred in inoculated compared to uninoculated groups; the inoculated average biomass in potting mix and regolith (2.23 and 0.29 g, respectively) was greater than the uninoculated group (0.11 and 0.01 g, respectively). However, no significant differences existed in NH4 composition between potting mix and regolith simulant. Linear regression analysis results showed that: i) symbiotic plant-bacteria relationships differed between regolith and potting mix, with plant biomass positively correlated to regolith-bacteria interactions; and, ii) NH4 production was limited to plant uptake yet the relationships in regolith and potting mix were similar. It is promising that plant-legume symbiosis is a possibility for Martian soil colonization.

Intercropping on Mars: A promising system to optimise fresh food production in future martian colonies

“…A study involving legume-Rhizobia symbiosis in Mars regolith simulants showed more nodulation in the MMS-2 regolith simulant compared to MMS-1, where MMS-2 contains added compounds such as Iron Oxide, Magnesium Oxide, Sulfates and Silicates [ 64 ]. Another similar study on legume-Rhizobia interactions in MMS-1 suggested that the high pH of the regolith may impair Fe uptake by the plants, Fe being a key factor for plants to sustain a healthy relationship with rhizobia, which would in turn negatively impact nodulation [ 65 ].…”

Microbial applications for sustainable space exploration beyond low Earth orbit

“…Increased Martian soil fertility through symbiotic relationships has been examined with clover ( Melilotus officinalis ), grown in simulated regolith that had been inoculated with the nitrogen-fixing bacterium, Sinorhizobium meliloti 56 . This study found that after three months, inoculated treatments produced greater clover biomass compared to uninoculated treatments, 0.29 g and 0.01 g, respectively.…”

A Comparison of Different Protocols for the Extraction of Microbial DNA Inhabiting Synthetic Mars Simulant Soil

“…In addition, many educational institutions use Mars simulant soils for demonstrations on Martian geology and extraterrestrial agriculture [13][14][15]. Furthermore, recent research demonstrates that microorganisms can effectively enhance soil nutrients available and facilitate crop growth in Mars simulant soil [16][17][18]. This highlights the importance of obtaining soil DNA to understand the interaction between microorganisms and Mars simulant soils, and to perform subsequent sequencing analysis of microbial functions.…”