Potential of Acidithiobacillus ferrooxidans to Grow on and Bioleach Metals from Mars and Lunar Regolith Simulants under Simulated Microgravity Conditions.

Anna H Kaksonen,Xiao Deng,Christina Morris,Yosephine Gumulya,Luis Zea,Himel Nahreen Khaleque

doi:10.3390/microorganisms9122416

Abstract

The biomining microbes which extract metals from ores that have been applied in mining processes worldwide hold potential for harnessing space resources. Their cell growth and ability to extract metals from extraterrestrial minerals under microgravity environments, however, remains largely unknown. The present study used the model biomining bacterium Acidithiobacillus ferrooxidans to extract metals from lunar and Martian regolith simulants cultivated in a rotating clinostat with matched controls grown under the influence of terrestrial gravity. Analyses included assessments of final cell count, size, morphology, and soluble metal concentrations. Under Earth gravity, with the addition of Fe3+ and H2/CO2, A. ferrooxidans grew in the presence of regolith simulants to a final cell density comparable to controls without regoliths. The simulated microgravity appeared to enable cells to grow to a higher cell density in the presence of lunar regolith simulants. Clinostat cultures of A. ferrooxidans solubilised higher amounts of Si, Mn and Mg from lunar and Martian regolith simulants than abiotic controls. Electron microscopy observations revealed that microgravity stimulated the biosynthesis of intracellular nanoparticles (most likely magnetite) in anaerobically grown A. ferrooxidans cells. These results suggested that A. ferrooxidans has the potential for metal bioleaching and the production of useful nanoparticles in space.

Highlights

In situ resource utilization (ISRU), defined as the use of local resources to produce space consumables, is increasingly gaining importance with long-duration missions such as those to Mars, as the resupply from Earth is cost-limiting
The ability of A. ferrooxidans to extract metals from lunar and Martian regolith simulants was evaluated under simulated microgravity and Earth gravity conditions
Under Earth gravity, the growth of A. ferrooxidans in Mars regolith simulant and Fe3+ (MRS) cultures was enhanced when cultivated with the Mars regolith simulant plus Fe2 (SO4 )3 (MRS vs. S in Figure 3, p-value = 0.0007)

Summary

Introduction

In situ resource utilization (ISRU), defined as the use of local resources to produce space consumables, is increasingly gaining importance with long-duration missions such as those to Mars, as the resupply from Earth is cost-limiting. Moon to Mars program, aiming to lay the foundation for a sustained long-term human presence on the lunar surface will require ISRU technologies that enable the production of commodities using natural resources from the Moon or other celestial bodies. Robust microorganisms can be used and potentially engineered using synthetic biology approaches as micro-factories for transforming in situ destination planet resources into useful products. It is known that microbes interact with minerals in the rocks or soils on Earth, contributing to the geochemical cycling of elements. Several chemolithoautotrophic microorganisms can dissolve valuable metals from minerals and wastes in the process called biomining [1,2].

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