Influence of spaceflight relevant conditions on survival of microbial isolates from the C.R.O.P. system

Abstract

The production of food and consequently the cultivation of plants on long-term space missions are essential, as vitamins degrade over time and supply missions are expensive and resource-intensive. A challenge in growing plants in space, particularly in hydroponic cultures, is their nitrogen supply. This could be ensured by the C.R.O.P. filter. This filter consists of a biofilm whose microorganisms can convert nitrogen from urea in the waste product urine into substances like nitrate that plants can absorb. Since the microbes in the biofilm are indispensable, it should be ensured that they can withstand the various conditions in space, such as increased radiation exposure and desiccation. To address this, thirty microorganisms were isolated from the C.R.O.P. system, with six of these isolates subjected to various stress tests to evaluate their resistance to X-ray, UV-C radiation, and desiccation. Initial results revealed that some of the organisms exhibited strong resistances. The human pathogen Pseudomonas aeruginosa showed high susceptibility to all stress tests, whereas Bacillus aryabhattai demonstrated only a 90 % reduction in survival after UV-C exposure up to 3000 J m⁻². Overall, all tested microbes were able to withstand a certain level of increased radiation, both non-ionizing UV-C and ionizing X-ray. However, non-spore-forming isolates in pure culture survived desiccation for up to eight days.