Science » Technologies and discoveries
Author`s name Alex Naumov

Arsenic-eating super-bugs promise cleaner future

Australian scientist have discovered an amazing arsenic-eating super-bug that can chomp its way through the deadly leftovers of a century of mining and farming to help clean up our landscape.

The microbe may also offer a low-cost way to help save tens of millions of people from the worst poisoning event on the planet.

The super-bug was identified after screening thousands of samples of microbes from soils heavily contaminated with poisonous arsenic which was once used to control parasites on sheep and cattle. At these sites arsenic is usually present in the highly toxic form arsenite, or as the less toxic arsenate. It is the highly toxic arsenite which is most difficult to remediate.

“It was a case of serendipity,” says Professor Megh Mallavarapu of the CRC for Contamination Assessment and Remediation of the Environment and the University of South Australia.

“We’d been looking for over a year at microbes that tolerate arsenic and DDT – and this one popped up. It takes in the highly toxic arsenite, and oxidises it to the much less dangerous arsenate form, which can easily be immobilised other methods.

“There are so many microbes in the soil we might easily have missed it – but luckily we didn’t.”

The bug holds hope of developing an efficient biological method for cleaning up the hundreds of thousands of arsenic stock dip sites in Australia, New Zealand, Argentina and other countries, places where arsenic-treated timber posts have been made or used, sites of old railway lines, as well as old gold-mining regions where arsenic flushes out of tailings dumps into surface and groundwater, posing a risk to those who drink it.

The microbe could also be used to cleanse household drinking water in Bangladesh, India, China and South East Asia where an estimated 100 million people face daily poisoning from arsenic in their well water, Professor Mallavarapu says.

Besides being known to cause cancer of the skin, lung, bladder, kidney, liver and uterus, arsenic is also linked to several skin diseases, nerve disorders, diabetes, lung disease, heart disease, suspected birth defects, liver and blood disorders, says CRC CARE Managing Director Professor Ravi Naidu.

“This is a truly momentous discovery by Professor Mallavarapu and his team, as it addresses one of the most intractable contamination problems facing almost all societies,” he says. ”They are to be congratulated on this important advance for Australian remediation science.”

“The beauty of this organism is that it performs the breakdown of toxic arsenite very efficiently,” says Professor Mallavarapu . “We isolated hundreds of arsenic-tolerant species - but this one breaks down the most toxic form of arsenic in a very efficient manner.”

“The microbe is completely harmless to humans, animals and the environment in other respects. It also tolerates other toxins such as cadmium and lead.”

“We can cultivate these microbes on a large scale and then put them into the contaminated soil or water. This would be an efficient and low-cost way to make them much safer for people living nearby, growing crops on contaminated land or drinking water that passes through it.”

The team is currently engaged in more detailed genetic screening to see if they can assess the potential to develop even more efficient pollution-busting organisms. A valuable outcome would be tools that provide a rapid test for the presence of arsenic in soil or water.

This would greatly accelerate the process of finding out which soils and groundwaters are most in need of remediation, and checking drinking water supplies to ensure they are safe, Professor Mallavarapu says.