Fresh Science

Melbourne scientists plan to harness the strange appetite of newly discovered Australian bacteria to help purify arsenic-contaminated water.

The research group, led by microbiologist Dr Joanne Santini of La Trobe University, is working out how to use bacteria that eat arsenic to clean up contaminated wastewater in Australian and overseas mining environments and drinking wells in Bangladesh and West Bengal, India.

“If the iron guts of bacteria that can eat arsenic without dying could be harnessed to process this waste, less damage would be done to the environment and hopefully, one day, fewer people on the subcontinent will get sick,” Dr Santini said.

“We hope the bacteria will one day be used in bioremediation – a biological process where bacteria that eat arsenic will be used to clean up the contaminated water.”

“It is theoretically cheaper and safer to use bacteria to clean up environmental mess than it is to use dangerous and expensive chemical methods that employ chlorine or hydrogen peroxide” Dr Santini said.

Dr Santini and her students are studying 13 rare bacteria that were isolated from gold mines in the Northern Territory and Bendigo, Victoria – the only lab in the world to do so.

Arsenic occurs naturally in rocks and in this form is harmless. But when exposed to air and water, the arsenic becomes soluble and toxic to plants, animals and humans.

Mining and boring rock for drinking wells can expose the rock-bound arsenic to air and water and turn it into two toxic forms: arsenate and arsenite. Arsenate is easy and safe to get rid of. But arsenite is not, and it is this form of arsenic Dr Santini hopes can be removed by the use of arsenite-eating bacteria on a mass scale.

One bacterium, NT-26, is an arsenite-munching champion. It eats arsenite and excretes arsenate. Dr Santini’s group has found the enzyme directly responsible for converting arsenite to arsenate and they are working to identify the same enzyme in the other microbes. They are also hunting for other proteins and genes involved in eating arsenite.

“In order to know how to best use these microbes for bioremediation we must first study how they eat arsenite,” Dr Santini said. “We can’t just plonk them into a biological reactor and hope for the best.”

“The knowledge from this research should allow us to set up a bioremediation system that will not only clean up mining waste water but perhaps provide the Bangladeshis and West Bengalis with safer drinking water.”

Dr Santini has a current Australian Research Council Discovery grant to study these arsenite-eating bacteria. She will be speaking to the public and school students about her work on Tuesday 19 and Wednesday 20 August at the Melbourne Museum.  

Joanne Santini: Appetite for arsenic

ARC Australian Postdoctoral Fellow La Trobe University

Appetite for arsenic

Bacteria that feed on arsenic

Australian arsenic-munching microbes could be used to clean up arsenic-contaminated water in mines in the western world and in drinking wells in Bangladesh and India.  I am researching how to use these microbes’ appetites to clean contaminated water.  This breakthrough research involves studying the microbes’ enzymes and genes.

Project description

Research on newly discovered Australian bacteria could help clean polluted mines and save the lives of villagers in developing countries.This is because they possess a rare appetite – they eat arsenic. These ten strains of bacteria, found at the Granites gold mine, Northern Territory, have the potential to safely clean mines contaminated with arsenic – an environmental problem in Australia, Canada, America and Britain. Arsenic is an element usually found in solid form in rock, where it does no harm.  But when such rocks are exposed to air and water, arsenic enters the ground water and becomes toxic to plants, animals and humans.  Mining does this when it disturbs rocks.

Arsenic in water comes in two forms: arsenite and arsenate.Arsenate is toxic but arsenite 100 times more so.Arsenite and arsenate levels in surface waters from abandoned gold mines are as high as 0.3 grams per liter – 600 times the maximum level allowed by international safety standards.  Groundwater from an old mine shaft in Bendigo, for example, has 0.012 grams per liter – 24 times the maximum.  In Bangladesh and India’s West Bengal, many villagers fall ill after drinking arsenic-contaminated water taken from bores sunk through rock.   Studies link use of this bore-water with arsenic-related cancers, blood diseases and jaundice.

It is safe and cheap to use chemicals to rid water of arsenate, but removal of the more toxic arsenite is expensive and difficult.To get rid of this arsenite, it must first be converted into its safer arsenate form.  Though chemicals such as chlorine and hydrogen peroxide can do this, the procedures involved are expensive and environmentally unsound.However, using arsenic-munching bacteria could be simpler, cheaper, quicker and safer.These microbes eat the arsenite and excrete arsenate. One microbe called NT-26 shows the most potential.

I have worked out how to best grow NT-26 in the lab, and sequenced the genes that allow it to eat the arsenite. I have also identified the NT-26 enzyme that allows it to convert the arsenite to arsenate.  This enzyme is found outside of the inner membrane, where it can prevent arsenite from entering the cell. My students and I are doing the same with the other strains of microbes from the NT.The knowledge gained will let us set up a biological system to banish arsenic contamination in Australia and give Bangladeshis and West Bengalis safer drinking water.

Personal details

Qualifications: PhD in 1999, La Trobe University, BScHons 1994, La Trobe University Department of Microbiology Department of Microbiology