A method for tracking the locomotion of an isolated microorganism in real time

An inexpensive, real-time recording system ("bug-tracker") for tracking the movements of an isolated microorganism was assembled using a close-up video system, a video memory card, and a personal computer. An isolated organism moving in an almost two-dimensional plane is viewed by the close-up video camera, and a selected video frame is digitized by the video memory card into 256 x 256 pixels (picture points). The pixels of the ith frame are subtracted from those of the i-lth frame to delete images other than that of the image of the moving organism. Windows with an optimized size are generated commonly in the ith and i-lth frame to reduce the number of pixels directly accessed by the computer, and the address of the pixel with the largest value inside the windows identifies the coordinates of the organism on the X and Y axes. By optimizing the size of a window for a given organism, the sampling for the X and Y coordinates can be made at times separated by approximately 0.2 to 2.0 seconds. Data are automatically filed on a floppy disk.