**3.10 Phototaxis**

Phototaxis is the movement towards or away from the light source. This type of movement is characteristic of phototrophic organisms and is also observed in plants. Prokaryotes use type-I sensory rhodopsin photoreceptors for phototaxis and it allows them movement towards steep light gradient. Cyanobacteria can also perform phototaxis but they also can perform it in two-dimension only through gliding on the surface. Eukaryotes have the ability to navigate through light vector in three-dimension in open water [22].
