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We could give bacteria a helping hand to tackle oil spills on land and at sea by equipping them with enzymes for breaking down hydrocarbons, according to new research. This could be much cheaper and more eco-friendly than other clean-up methods.

鈥淎t the moment, there really are not any good ways to clean up oil spills,鈥� says Katherine French at the University of California, Berkeley. Common methods include dumping the contaminated soil elsewhere or spraying chemicals that can themselves be damaging.

Some microbes naturally possess enzymes that can break down the hydrocarbons that make up oil, but these microbes are seldom found near oil spills. Instead, French and her colleagues want to give local bacteria the genes to make such enzymes themselves.

In addition to their main genome, almost all bacteria also carry extra pieces of DNA called plasmids that can be passed on to other species of bacteria. French and her colleagues created a plasmid with genes for five enzymes involved in breaking down hydrocarbons, then added it to a strain of E. coli.

When the E. coli were added to highly polluted soil from an oil refinery, they聽all died within five days, but the plasmid was rapidly passed on to more than a dozen different wild species of bacteria, which then began breaking down the oil.

The total amount of hydrocarbons in the soil fell by almost half in 60 days. Levels in samples to which the plasmid wasn鈥檛 added fell by less than 5 per cent.

French thinks adding genes to local microbes in this way could be more effective than genetically engineering a microbe to do the job, as it might not cope in a new environment.

鈥淚t鈥檚 a super-interesting idea,鈥� says James Hall at the University of Liverpool in the UK, who studies plasmids. Manipulating whole communities of microbes by adding genes in this way could have all kinds of uses, he says.

However, Hall says the plasmid could remain in the bacteria even after the hydrocarbons are gone and could also be incorporated into the main genome of bacteria.

The extra genes wouldn鈥檛 have any effect on human health, says French. 鈥淗aving petroleum in the soil is more dangerous than having GM bacteria.鈥� In many parts of the world, oil spills never get cleaned up, she points out. Fumes, as well as contaminated water and food, can harm people鈥檚 health.

Wild bacteria with an engineered plasmid would be regarded as genetically modified organisms in many countries, making it difficult to get approval for field trials. But there are natural plasmids containing genes for hydrocarbon enzymes, says Hall. In theory, no approval would be needed to use these plasmids.

Using microbes that naturally possess the enzymes to clean up sites is better than using chemical treatments, says Stephen Hawkins at the University of Southampton in the UK, who has studied how contaminated sites recover.

鈥淪ome conventional treatments such as dispersants can make things worse. They can kill off the microbes that break down crude oil,鈥� he says. 鈥淏ut I would be very, very wary about releasing genetically modified organisms into the environment.鈥�

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