Abstract
Phototaxis is a mechanism that allows cyanobacteria to respond to fluctuations in the quality and quantity of illumination by moving either towards or away from a light source. Phototactic movement on low concentration agar or agarose plates can be analyzed at macroscopic and microscopic scales representing group behavior and single cell motility, respectively. Here, we describe a detailed procedure for phototaxis assays on both scales using the unicellular cyanobacterium Synechocystis sp. PCC 6803.