As humans look to become interplanetary species, one of the key requirements to survive long-duration flights to other planets or beyond Earth will be life-sustaining elements. Researchers have now succeeded in mining metals from microbes without using the traditionally required heavy machinery. Biomining has emerged as an alternative to traditional mining of metals when one doesn't have vast natural resources, heavy machinery and is travelling in space with nothing but complete vacuum outside the spacecraft. Biomining, therefore, offers a way to obtain required materials for use on other planetary bodies rather than transporting them from Earth.
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| Preflight fluorescence microscopy image of biofilm of Spingomonas desiccabilis growing over and into the surface of a basalt slide as part of Biorock experiment. Organisms are stained with DNA binding dye, Sybr Gold. Growth can be seen into the rock cavities. Image © NASA |
Vanadium is an element commercially added to steel to fabricate high strength, corrosion-resistant materials that could be used in buildings, tools, and construction processes on other planets. “Mining is a necessary part of civilization, and it has been going on since people first started settling in villages and cities,” says Charles Cockell, Biorock principal investigator and professor at the UK Centre for Astrobiology at the University of Edinburgh. Using microbes to do that mining provides advantages over common chemical methods of extracting elements from soil. “Chemical methods of remediation can be very damaging, whereas bioremediation and bioleaching is environmentally friendly, and produces fewer toxins,” Cockell says. “It is low energy demand. You give the microbes some food, and they go about their business of mining.”
Biomining with microbes also has the advantage of being compact, which is convenient for deep space exploration in which space for materials is limited when launching from Earth. But whether this process would work in microgravity was uncertain. “Microgravity has an effect on bulk fluids, and there is no convection or sedimentation in microgravity,” says Cockell. Because of this effect, the team suspected that altered gravitational conditions might negatively influence biomining by limiting the interactions of microbes of the same species, preventing the mixing of microbes in fluid.
To test whether microbes could biomine vanadium in altered gravitational conditions, the team filled a KUBIK incubator on the space station with liquid growth media, a mixture of nutrients designed to support the growth of microorganisms. The team then grew selected microbes known to break down rocks under microgravity and simulated lunar and Martian gravity conditions. The researchers also supplied the microbes with basalt, a constituent of the lunar and Martian surfaces.
“We were surprised gravity did not have an effect. But we think the reason is that for the period of the experiment, 21 days, the microbes were able to grow to their maximum concentration, even in the absence of sedimentation or convection on the space station. Therefore, they were able to mine in the same way, even in different gravity conditions,” said Cockell.
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