Mercury-loving bugs speed help for toxic spills hazards

Scientists say they have engin-eered bacteria that can mop up mercury, a step forward in the goal of using “bioremediation” to cleanse toxic chemicals from the environment.

Mercury pollution of water and soil by industrial spills or gold mining is a major hazard because the chemical accumulates up the food chain, and tackling the pro-blem is prohibitively expensive.

A team led by Oscar Ruiz of the Inter-American University of Puerto Rico say they inserted two mercury-friendly genes into the common intestinal germ, Escherichia coli.

The genes controlled a protein called metallothionein and an enzyme known as polyphosphate kinase, both of which bind to metals in order to prevent toxicity.

The researchers immersed the engineered bugs in a nutrient solution to which high doses of mercury had been added. The E. coli with genes for polyphosphate kinase grew in mercury levels 16 times higher than the maximum for normal strains of the bug.

Even more impressive, those with the genes for metallothionein flourished in 24 times the maximum mercury level. After five days, chemical analysis showed the bacteria had absorbed up to 80 per cent of the mercury to which they had been exposed.

Dr Ruiz said the experiments opened the way to a viable tool to not only clean up mercury but also recycle it, using electrochemistry to extract the chemical from the bacteria.

“Once [mercury] pollutes a body of water it is very difficult to clean, due to the intense process of removing and transporting large volumes of water to an external location, then treating the contaminated water, and finally disposing of the treated water,” said Dr Ruiz.