Metal sponges and iron-eating bacteria

Danielle FortinDanielle Fortin in her geomicrobiology laboratory in Marion Hall with Master’s students Ed Bryson (in the background) and Alyssa Dunbar.

“These iron oxides are sponges. When they’re in water, we know that soluble contaminants like metals stick to their surface.”

– Danielle Fortin

Every year, the Canadian mining industry generates more than 650 million tonnes of waste laden with heavy metals and chemicals that can have devastating effects on the environment and on humans.

Given the serious implications involved and the astronomical cost of decontamination projects, governments and mining companies alike are all ears when it comes to advice and possible solutions. Enter a University of Ottawa researcher and her two faithful allies: bacteria and metals.

Danielle Fortin, a professor in the Faculty of Science, is among the pioneers of geomicrobiology in Canada. At the junction of living organisms and inorganic matter, the field holds tremendous potential on a broad scale, from the decontamination of mining waste to the search for life in the universe.  

In her geomicrobiology lab — Canada’s first — at the Department of Earth Sciences, Fortin examines the propensity of a type of iron oxide (plain old rust) for retaining or releasing contaminants in tandem with bacterial activity.   

What is particular about such “biogenic” iron oxides is that they form near or on the cell wall of bacteria. This property, which affects the oxides’ size and structure, allows them to easily retain or capture elements on their surface. “These iron oxides are sponges,” explains Fortin. “When they’re in water, we know that soluble contaminants like metals stick to their surface.”

That begs the question: Can iron oxides play a role in the decontamination of mining waste? Yes, they can, according to Fortin. But researchers first have to find out how they will react in the longer term and under different conditions.

One of Fortin’s projects, funded by the Natural Sciences and Engineering Research Council of Canada, focuses on the stability of iron oxides. The goal is to understand how the oxides age and how they react under changing conditions, such as a lack of oxygen or the presence of bacteria.

“For example, if you dig into mining residues, when you get down about 15 centimetres, the residues are black, meaning there’s no more oxygen,” she explains.  “In these conditions, other bacteria known as ‘iron reductive’ become active and start reducing or dissolving the iron oxides, so everything that was stuck on the surface of the oxides goes back into the environment.”

By studying the effects of bacteria on iron oxides, it will be possible, among other things, to gauge the long-term environmental risks of tailings sites and, in the process, to set priorities for decontamination.    

“What’s more, to use biogenic iron oxides to neutralize contaminants, we absolutely have to ensure there’s always a bit of oxygen present at the site,” adds Fortin.

The researcher and her team of graduate students are also developing geochemical tools that can more accurately determine both the presence and nature of a mineral deposit, by assessing, for instance, how well the plants in the area reveal traces of the deposit. This helps avoid fruitless and damaging drilling.

Fortin is also interested in how living organisms, even long after their disappearance, can leave traces in inorganic matter. This phenomenon has weighty implications in the field of exobiology, the study of possible life forms in the universe. “Can we find a certain mineral or a certain chemical combination that can be attributed solely to the presence of life?” asks Fortin, whom NASA invites every year to assess research projects focusing on chemical or mineralogical proof of life or on future expeditions to Mars.

Since their research extends into so many areas, Fortin and her students will benefit from their new quarters in the Advanced Research Complex, where they will have access to the latest equipment and to a perfect setting for exchanging ideas — critical assets for research teams working across disciplines.

“My students have all been trained in very different scientific fields — geology, chemistry, microbiology, physics and so on,” she says. “Still, they are all fascinated by the interaction of living organisms and inorganic matter.”  

 

by Sophie Coupal

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