Computer-linked automated method for measurement of the reversal frequency in phototaxis of Halobacterium halobium.

Abstract

A computer-linked automated system was developed for counting the number of moving microorganisms under a microscope. The method discriminates whether the microorganisms showed reversals or smooth swimming. The features of the system are commercial I/O [input/output] devices, and a microcomputer used to process the moving pictures; fast processing is accomplished by bit operations for computing the correlation matrix, and pseudo moving objects are processed on the later frames; and a number of cells on the frames are processed in a short time, with occluded individuals on a frame being neglected. The system was used to study the phototactic behavior of H. halobium. High intensity background illumination caused a decrease in the sensitivity of the behavioral response of the cell to the attractant light.