Biological Reduction of Perchlorate in Martian Regolith Simulant Using Azospira Oryzae

Establishing a sustainable human presence on Mars will require in-situ resource utilization (ISRU) to reduce costly and inefficient resupply missions. Despite containing many of the requirements for agriculture, Martian regolith is contaminated with toxic levels of perchlorate (ClO4-), threatening human health and agricultural success. Biological remediation using perchlorate-reducing bacteria offers a promising approach to address these challenges. This study investigated the perchlorate-reducing ability of Azospira oryzae, a facultative anaerobe capable of converting ClO4- to chloride (Cl-) through dissimilatory respiration. A. oryzae was cultured in Martian regolith simulant (MGS-1) amended with 0.0%, 0.5%, and 1.0% perchlorate by weight. Three assays were completed to assess reduction: OD600 measurements to track bacterial growth, a methylene blue colorimetric assay to measure perchlorate concentration, and a silver nitrate titration to measure chloride production. The use of multiple assays aimed to depict the depletion of perchlorate and production of chloride, providing insight into the full scope of this reduction pathway. The findings contribute to our understanding of how microbes may be applied in future perchlorate bioremediation efforts as part of ISRU strategies for extraterrestrial agriculture.