Single-cell level continuous observation of microorganism galvanotaxis using high-speed vision

A novel system for measurement of motile microorganism galvanotaxis using high-speed vision is presented. Our goal is to construct a smart microsystem composed of many controlled microorganisms called "Organized Bio-Modules" (OBM). The OBM system utilizes galvanotaxis (intrinsic reaction to electrical stimulus) of microorganisms for actuation. For evaluation of taxis, continuous observation of a moving single cell in a sufficiently large working area without fixation is needed. Using high-speed vision, we developed a system for continuous evaluation of galvanotaxis of freely swimming cells in a large area at the single-cell level. Experimental results demonstrate the continuous measurement of galvanotaxis of a Paramecium caudatum cell moving in a 3.5-mm-square area for 18 s with 1 μs precision.