MSU researchers show how microbes can withstand a toxic metal and open the door for applications in recycling and remediation
MICHIGAN STATE UNIVERSITY
Research news
PICTURE: THIS GEOBACTER CELL, WHICH LOOKS A BIT LIKE A GRAY PEANUT IN THIS MICROSCOPE IMAGE, IS SPOKEN WITH A DARK COATING OF COBALT MINERALS THAT WOULD BE TOXIC … View more CREDIT: HUNTER DULAY, MS
When Gemma Reguera of Michigan State University first proposed her new research project to the National Science Foundation, one reviewer replied that the idea was not “environmentally relevant.”
Because other reviewers and the program manager disagreed with this view, NSF funded the proposal. And now Reguera’s team has shown that microbes are capable of an incredible feat that can help reclaim a valuable natural resource and absorb toxic pollutants.
“The lesson is that we really need to think outside the box, especially in biology. We only know the tip of the iceberg. Microbes have been on earth for billions of years and the thought that they can do nothing excludes so many ideas and applications from us, ”said Reguera, professor at the Institute of Microbiology and Molecular Genetics.
Reguera’s team works with bacteria found in soil and sediments known as geobacter. In their latest project, the team investigated what happened to the bacteria when they encountered cobalt.
Cobalt is a valuable but increasingly scarce metal that is used in batteries for electric vehicles and alloys for spacecraft. It is also highly toxic to living things, including humans and bacteria.
“It kills a lot of microbes,” said Reguera. “Cobalt invades your cells and causes havoc.”
But the team suspected that Geobacter might escape this fate. These microbes are a tough bunch. They can prevent uranium contaminants from entering groundwater, and they can be self-sufficient by drawing energy away from minerals containing iron oxide. “You breathe rust,” said Reguera.
Scientists know little about how microbes interact with cobalt in the environment, but many researchers – including a license examiner – believed the toxic metal would be too much for the microbes.
However, Reguera’s team challenged this thinking and found that Geobacter are effective cobalt miners who extract the metal from rust without it penetrating their cells and killing them. Rather, the bacteria essentially coat themselves with the metal.
“They form cobalt nanoparticles on their surface. They metallize themselves and it’s like a shield that protects them, ”said Reguera. “It’s like Iron Man when he puts the suit on.”
The team published their discovery in the journal Frontiers in Microbiology. The research article first appeared online at the end of November 2020. The Spartan team included Kazem Kashefi, an assistant professor in the Department of Microbiology and Molecular Genetics, and graduate students Hunter Dulay and Marcela Tabares, who are “two amazing and relatively young investigators,” Reguera said.
She sees this discovery as a proof of concept that opens the door to a range of exciting possibilities. For example, Geobacter could lay the foundation for a new biotechnology designed to recover and recycle cobalt from lithium-ion batteries, reducing the country’s reliance on foreign cobalt mines.
It also invites researchers to study Geobacter to ingest other toxic metals that were previously believed to be death sentences for the bacteria. Reguera is particularly interested to see if Geobacter can help eliminate cadmium, a metal found in industrial pollution that disproportionately affects America’s most deprived communities.
“This is a reminder to be creative and not limit your options. Research is the freedom to explore, to seek, and to seek and to seek, ”said Reguera. “We have textbook opinions on what microbes can and should do, but life is so diverse and colorful. There are other processes waiting to be discovered. “
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This work was supported by the NSF’s Geobiology and Low Temperature Geochemistry Program and a Hatch grant from the US Department of Agriculture’s National Institute of Food and Agriculture.
(Note for the media: Please add a link to the original article with the online reporting: https://doi.org/10.3389/fmicb.2020.600463)
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