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Iron-Hungry Compound Can Glow as Satisfaction Grows

By Ben Hardin
May 14, 1999

Detecting trace levels of iron in biological samples within two minutes is now possible with a new procedure developed by Agricultural Research Service scientists.

In the new procedure, the scientists used a special chemical, called a pyoverdine, produced by the beneficial bacterium Pseudomonas fluorescens. Pyoverdine can be used to create a biosensor. Biosensors, which rely on living organisms or their by-products to identify and gauge chemical concentrations, can be immersed in liquids and monitored by computers.

Under ultraviolet light, the pyoverdine normally takes on a yellow greenish glow that quickly subsides as iron is absorbed. But the researchers saw a strikingly different scene when they mixed a solution, called an acetate buffer, with the pyoverdine and then added the combination to test samples containing as little as 10 parts per billion iron. Instead of quickly subsiding, the glow steadily increased for several minutes. The more iron present, the slower was the rate of increase.

The researchers have applied for a patent on the iron detection method.

Now, ARS is seeking an industrial partner to develop the pyoverdine-acetate combination for an analytical process known as kinetic fluorometry. For example, in some parts of the world, a simple kit might be used to monitor increased iron levels in urine as patients are treated with an antimalarial drug. Or someday more sophisticated tools, fiber-optic biosensors, might monitor iron during water, food, pharmaceutical and chemical processing.

ARS is the U.S. Department of Agriculture's chief research agency.

Scientific contact: Patricia J. Slininger, ARS National Center for Agricultural Utilization Research, Peoria, Ill., phone (309) 681-6286, fax (309) 681-6427,