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Genetic Approach Purifies Drinking Water

One of the most pressing global problems is the supply of safe, clean drinking water. Millions, if not billions, of people drink water contaminated by bacteria, fungi and viruses that make it unsafe. Water treatment technologies exist, but many are expensive or they're too slow to supply enough water to the many people who need it. Rose Hoban tells us about a new approach to water purification.

Environmental engineer Claudia Gunsch has been trying a new approach to the problem of water purification. The Duke University professor is working with something called RNA interference, or RNAi, a genetic technology already in use to treat cancer.

RNA is different from DNA; it's a single strand of genetic material. In cells, RNA binds to other single-strands of RNA to reproduce itself. Gunsch says RNAi acts in the same way, binding to targeted strands of RNA in cells.

"And when it binds, it inactivates [the RNA] and gets chopped up into smaller pieces, rendering it inactive," Gunsch explains. "And so, if you can target a gene that is essential for the cell to function, then you're essentially disabling that microorganism."

Gunsch targeted genes present in some harmful bacteria commonly found in water. She's one of the first people to use RNAi in this way. "We have taken cells and mixed some of this RNAi in a single container and then we've monitored for the activity of specific genes," she says. "We have a nice system, which is based on color, and so it makes it very easy to determine what the activity of that gene is… it goes from yellow to clear, for instance. So it makes it really easy for us to see if it's working."

Gunsch says so far, she's only treated small amounts of water with RNAi. For large-scale operations, she says it might be possible to integrate the RNAi into a filter, such as a carbon filter. The carbon would de-activate chemical toxins as the RNAi kills microorganisms.

Gunsch says this technique would increase the efficiency of some simple water purification systems that use sunlight, frequently used by people in the developing world. She explains, "They put water in glass bottles and they put them on the roofs of their house and leave them out there for … several hours and then rotate them every so frequently and the sunlight kills the pathogens." Gunsch says while that process works fairly well, incorporating RNAi carbon filters would remove even more harmful microorganisms.

Gunsch estimates she's several years away from something that could be used on a larger scale, but believes this new technology holds promise.

Gunsch's co-author, Sara Morey, presented their research in Boston recently, at the annual meeting of the American Society of Microbiology.