Many parts of the world, particularly in poorer countries, need better tools for identifying unsafe drinking water. A test developed by researchers at the University of Bristol, United Kingdom, seems to show potential as a low-cost technique for detecting common bacterial contamination in water supplies. The announcement appeared in July 2014 in the journal Environmental Science & Technology.
The Bristol team developed a simple visual indicator that signals the presence of Escherichia coli bacteria in water by a distinctive orange-to-pink color change. No additional laboratory processing or special equipment is required. Using a small amount (0.1 mg) of the indicator resorufin β-d-glucuronide, the researchers were able to detect as few as 10 E. coli in 100 ml of water, according to their published paper. See also: Escherichia
In chemistry, indicator compounds change color when they are converted from one structural form to another. Some of the best-known examples are the acid-base indicators, which change color when the presence of an acid or base converts them from their molecular to ionized forms. Resorufin β-d-glucuronide changes color when an enzyme in E. coli, β-glucuronidase, catalyzes the hydrolysis of resorufin β-d-glucuronide to produce glucuronic acid and the pink dye resorufin. Because β-glucuronidase is not common to other bacteria, the color change selectively indicates the presence of E. coli. See also: Acid-base indicator; Dye; Enzyme; Hydrolysis
Although not all E. coli cause disease, they are the most common of the fecal bacteria (coliforms) and their presence suggests the potential for contaminated water. Development of a simple, inexpensive, and sensitive test for coliform pollution is important in low-income countries for assuring the quality of their drinking water, especially in remote regions. Development of a lower-cost test would also allow for more frequent testing. See also: Escherichia coli outbreaks; Medical bacteriology; Water-borne disease; Water pollution; Water resources
The researchers estimated in their report that if resorufin β-d-glucuronide were synthesized using a low-cost method they developed, the 0.1 mg of indicator required for a test would cost $0.01, compared to $0.05 to $0.10 for currently available E. coli indicators, which are either more expensive or require more material because low-intensity colors are generated.