Marina Anteljević

The human colonisation of space is no longer confined to the realm of science fiction. Among various celestial bodies, Mars has emerged as a primary target for long-term human settlement in the future. One of the major challenges in such missions is ensuring a sustainable food supply. Transporting food across such vast distances is both costly and impractical, prompting growing interest in space farming and the use of in situ resources, such as Martian regolith, for plant cultivation. In this study, we explored the potential of growing watermelon (Citrullus lanatus) under simulated Martian conditions using a substrate which mimics the composition of Martian regolith. To mitigate nutrient deficiency, the seeds were treated with plant growth-promoting bacteria (PGPB) isolated from the rhizosphere of Miscanthus × giganteus grown in heavy metal-contaminated soil, yielding bacterial strains tolerant to the metal-rich and nutrient-poor conditions analogous to those of the Martian regolith simulant. Statistically significant differences in the plant growth parameters - including height, root length, fresh weight, and leaf area - were observed between the plants grown on soil and regolith substrates, while the chlorophyll content showed no significant variation, suggesting a preserved photosynthetic function despite abiotic stress. Additionally, seed inoculation with a bacterial consortium consisting of Pseudomonas chlororaphis, Bacillus safensis, and B. cereus/thuringiensis improved the germination rates compared to the untreated control. This research represents the first attempt to cultivate watermelon in a Martian regolith simulant and highlights the potential of PGPB as a promising strategy to enhance plant performance under extreme conditions. Further studies are needed to optimise microbial consortia and regolith amendments for future space agriculture applications.

Bacillus species are among the most researched and frequently applied biocontrol agents. To estimate their potential as environmentally friendly microbial-based products, reliable and rapid plant colonization monitoring methods are essential. We evaluated repetitive element-based (rep) and Random Amplified Polymorphic DNA (RAPD) PCR (Polymerase Chain Reaction) genotyping in a diversity assessment of 251 strains from bulk soil, straw, and manure samples across Serbia, highlighting their discriminative force and the presence of unique bands. RAPD 272, OPG 5, and (GTG)₅ primers were most potent in revealing the high diversity of a sizable environmental Bacillus spp. collection. RAPD 272 also amplified a unique band for a proven biocontrol strain, opening the possibility of Sequence Characterized Amplified Region (SCAR) marker design. That will enable colonization studies using the SCAR marker for its specific detection. This study provides a guide for primer selection for diversity and monitoring studies of environmental Bacillus spp. isolates.