Modified plant clears up deadly water toxin

Plants may be a useful tool in clearing water of harmful toxins produced by blue-green algae, new research indicates.

Some blue-green algae (cyanobacteria) — which grow in warm, nutrient-rich waters  — produce toxins that can severely damage the liver or nervous system. The effects of the toxins range from a mild illness to rapid death. They can remain in water supplies after the algae have been killed.

A team at St George’s Medical School, part of the UK-based University of London, has modified tobacco plants to secrete antibodies from the roots that then bind to microcystin-LR — the most common cyanobacteria toxin in water — rendering it harmless.

"A toxin that is bound to antibodies should be easier to remove from the environment and also is likely to be less harmful," said Pascal Drake, a biotechnology researcher at St George’s Centre for Infection. The antibodies could also be used in simple and cheap tests to see if toxins are present in water supplies, he said.

Tobacco plants, grown hydroponically in the lab, were chosen for the first phase of this research, reported last month (March) in The FASEB Journal, because "they are easy to work with and genetically engineer", said Drake. The next step will be to try and modify aquatic plants, which will be more suitable for large-scale treatment of water. Drake anticipated that this "wouldn’t be too problematic".

The research is still at an early stage, but it may ultimately lead to an affordable method of keeping water free of toxins. The scientists are also looking to modify plants that can extract toxins from water and store them in their leaves, so that removing the plants also removes the toxins.

In developing countries, the emphasis on disinfecting water so that it is free of pathogens — for example the bacterium that causes cholera — means that the removal of cyanobacteria toxins has often been overlooked, Tom Hall, a consultant at the UK-based Water Research Centre, told SciDev.Net.

He said that although this research is very interesting "at present activated carbon offers a relatively easy way of treating water supplies in developing countries". Drinking water can be filtered through carbon as part of the water treatment process, and small filters can be plumbed into water supplies for villages.

One litre of activated carbon can treat about 50,000 litres of water, said Hall. But it is not possible to remove toxins by simply adding activated carbon to lakes or reservoirs.