Light is an important and ubiquitous environmental signal that regulates bacterial metabolism and growth. On one hand photosynthetic bacteria swim to the zones with light intensity optimal for the functioning of the photon-driven carbon assimilation. On the other hand, some phototrophic bacteria also sense and capture light to derive energy for metabolisms other than photosynthesis. Beside the phototrophic bacteria, certain microbes use the light only for the purpose of communication and environmental positioning. Large variety of photosensory proteins is encoded in the bacterial genomes and responsible for these physiological functions. Here, we review the light-induced physiological and behavioral responses and the mechanism of light mediated signaling in bacteria, especially in nonphototrophic bacteria.