Biotinylated bacteria were immobilized onto biotin/avidin modified electrode surfaces. Firstly, an electrospotting deposition method, followed by fluorescence microscopy, showed that bacteria were specifically grafted onto a gold surface. Fluorescence intensity versus the quantity of bacteria deposited on the surface was correlated, allowing determination of the microbial saturation point. Secondly, biotinylated bacteria were immobilized onto a glassy carbon macro-electrode in order to assess immobilized bacterial denitrification activity. During a 7-day trial, the modified electrode completely denitrified 5 mM nitrate, with a rate of 1.66 mM/day over the first 3 days. When the same electrode was placed in fresh nitrate solution, the denitrification rate dropped to 0.80 mM/day. Crucially, the immobilized bacteria did not become detached from the electrode during the study.