Making a meal out of arsenic

Scientists in Melbourne plan to use arsenic eating bacteria to clean up contaminated wastewater in Australian and overseas mining environments and drinking wells in the Indian subcontinent.

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.

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 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,’ concluded Dr Santini.

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