Application of microbial cells as multistep catalysts in potentiometric biosensing electrodes

The advantages of using intact microbial cells to mediate complex reaction sequences in the construction of biosensing electrodes are domonstrated. A potentiometric sensor was developed for nitrilotriacetic acid (NTA) in which a strain of Pseudomonas sp. was coupled to an ammonia gas‐sensing electrode. the bacterial cells carry out a four‐step reaction sequence to produce the measured species, ammonia, from NTA. The resulting microbial electrode responded to NTA in the concentration range of 1 × 10 −4 M to 7 × 10 −4 M , with a slope of 35‐40 mV/decade. The electrode was stable for up to one month.