Australasian Science Magazine

Joël Brugger (left) and Frank Reith (right) looking for gold in organic-acid-rich waters in Minas Gerais.

By Alex Perry

South Australian scientists have negotiated with armed gangs in lawless areas of Brazil in a brave mission to study gold deposition processes there.

Many people imagine a typical scientist's workplace to be a sterile white laboratory littered with microscopes and specimens, but this hasn’t been the case for some intrepid researchers who have trekked through Brazilian jungles to negotiate with armed and dangerous gangs in the hunt for precious metals.

A team led by Prof Joël Brugger of the South Australian Museum and Dr Frank Reith of the University of Adelaide travelled to the Brazilian mining state of Minas Gerais, about

700 km north of Rio, to take fresh samples of gold from the area in order to preserve biofilms on the surface of the grains. However, collecting material from the diamond and gold fields of Minas Gerais is far from easy – or safe.

“The people live on a few dollars a day, and life is not that valuable,” Brugger says. “We needed access to mine sites so that we could get samples and compare them to other areas, but the sites were controlled by diamond and gold-hunters (garimpeiros).”

The team has been studying gold deposition in Australia and New Zealand, and wanted to compare this with samples taken from the tropical environment in Brazil, in particular how bacteria may interact with the gold. The research could lead to faster and more efficient means of detecting gold in the environment.

The team travelled to the towns of Diamentina and Ouro Preto, and discovered the limits of a 1.5-litre combie Fiat with little horse power on dirt roads and steep hills in the tropical rain without GPS.

Before speaking with the gatekeepers of the gold, a visit to the towns’ mineral stores and conversations with the townsfolk were necessary. “You’ve got to drink coffee, eat cheese – do a lot of warming up,” Reith explains. “Eventually you come to the point where you can say what you’d like to do. If you just go in you might not get out alive.

“We said we were medical doctors looking for samples for our research. Things can change quite quickly. It was a bit iffy because they are law-free areas. I don’t think there are police going there.”

The team’s research into both gold and platinum is of international significance and will service many industries that use the metals. “Brazil offers one of these unique opportunities to collect the grains because it is so rich in minerals,” Brugger says.

Overcoming intense heat, disorientation, disease-carrying insects and a lack of technology, the scientists used good humour and perseverance to negotiate access to the area they wanted to study. “Thankfully, a local geologist agreed to guide us to the region – that got us started and gave us a good idea of how things work in the gold and diamond fields,” Brugger says.

“We found a young man who spoke English. Finally he agreed to present us to the garimpeiros. We ended in a little car with someone who only spoke Portuguese – and none of us spoke a word of it!”

“He took us into a favela,” Reith continues. “As soon as you drive in there, every man and his dog comes out. He stopped and his phone wasn’t working. He had to call the ringleader across the river.”

“You absolutely do not enter without being announced, otherwise I don't want to think about what would happen to you,” Brugger says. “The guys were nice but a bit scary!”

The team managed to negotiate with gestures that they'd like some gold samples with bacteria on them. “The miners use soap in the final step for washing out the gold. It was quite a feat to explain that we wanted the dirtiest gold possible to keep the bacteria samples on it,” Brugger explains.

While it was difficult surviving armed and dangerous gangs, heavy rainfall, bogged cars, tropical insects and poverty-stricken regions without facilities, the scientists remained upbeat about their exciting field trip. The adventure was not without its pleasures: the group admired beautiful minerals, worked in stunning landscapes, lodged in romantic Portuguese imperial cities and enjoyed fresh food prepared in Brazilian roadhouses.

Now back in Adelaide, the researchers will use their prized samples of Brazilian gold, analysing the effect of bacteria from the unique deposits. “This is really fundamental work because we have no idea what we’re going to find,” Brugger says. “How do immobile precious metals move around? We want to show that bacteria help make them soluble, and understand the complex mechanisms bacteria use to survive in the unique environment that the surface of a gold grain represents.

“We are using state-of-the-art electron microscope imaging techniques to observe the presence of biofilms on the gold grains. A biofilm is effectively a layer of ‘slime’ covering the grain. We use a method called ‘focused ion beam’ to dissect the biofilm within the electron microscope, revealing, for example, the presence of nanoparticles of gold. We then extract the DNA from the gold grains and identify the genes present.

The research could have wide commercial implications. “With this information we can figure out which bacteria live on a particular grain, and investigate the possible pathways of gold dissolution and precipitation,” Brugger says. “For Australian grains, we were surprised that the same types of bacteria and pathways seem to be active from semi-arid conditions to the tropical north.

“Are the same organisms at work in Brazil? Once we think we have identified a particular pathway of gold mobility, we perform in vivo experiments to test the hypothesis and illustrate potential industrial applications.”

The molecular-level understanding of the genetic pathways that enable bacteria to dissolve gold or to precipitate nano­particles of the metals is the first step in developing many applications in the mining industry, including new ways of exploring for buried gold deposits by using DNA from the soil and groundwater; biosensors that can trace tiny amounts of gold underground or in minerals processing plants; or alternatives to cyanide-processing inspired from these bacteria that are able to move gold.