Researchers at Purdue University in the US have develo ped a new technique using sensors to constantly monitor the health of bacteria critical to wastewater treatment facilities. They have also verified a theory that copper is vital to the proper functioning of a key enzyme in the bacteria. The new method senses minute changes in chemistry related to bacterial health and yields results immediately, unlike conventional technologies, which require laboratory analyses taking at least a day.
This immediacy could make it possible to detect when bacteria are about to stop processing waste and correct the problem before toxins are released into waterways, said Eric McLamore, a postdoctoral research associate in civil engineering (Fig.1). The technique is a departure from conventional methods which require bacterial 'biofilms' be damaged or destroyed during testing.
"It's important to monitor intact living specimens to obtain accurate data, and our approach is both non-invasive and a real-time technique," said Marshall Porterfield, an associate professor of agricultural and biological engineering.
The biofilms are a matrix of wastewater-treatment organisms that coat natural or synthetic surfaces. A healthy population of the bacteria must be maintained for wastewater treatment facilities to operate properly, McLamore said.
The researchers used the method to study a type of bacterium called Nitrosomonas europaea. The microorganisms are referred to as nitrifying bacteria because they convert toxic ammonia from human wastes and fertilizer runoff into compounds called nitrites, which are further broken down by other bacteria into harmless nitrogen gas.
Sensor data shows how well the bacteria are absorbing ions, or electrically charged atoms and molecules, from the wastes. The 'filtering flux sensor' measures ammonia and nitrite to reveal the ion flux, or how many ions are being transported into and out of the biofilm per minute.
The sensor probe moves robotically back and forth every three seconds, capturing data in two locations. The method is called self-referencing because it compares the difference between measurements taken in two positions with the same sensor. Using a single sensor to take measurements in two locations is critical for revealing rapid changes in concentration. As individual sensors have slightly differing performance, comparing data from two different sensors does not yield precise results.
A specific enzyme in Nitrosomonas europaea converts the ammonia to nitrite. The researchers used their new technique to verify a theory proposed decades ago that copper at the enzyme's active site where ammonia binds is critical to enabling the conversion.
The research is published in 15th February issue of Biotechnology and Bioengineering.
