Abstract
Phototropism is the directional growth in response to directional light, which is widely observed in eukaryotes such as higher plant, Phycomyces and Vaucheria. However it has been barely reported from prokaryote. Recently, we found that filamentous cyanobacterium Rivularia sp. IAM-M-261 exhibits positive phototropic response.
White light most effectively induced the positive phototropic response, but monochromaic light of 400nm to 750 nm did not. Monochromatic light induced the phototropic response under irradiation of other monochromatic light as background light. Namely, the positive phototropic response toward violet to blue light was observed when green, orange or red light was used as background light. In addition to this, the positive phototropic response towards green to orange light was also observed when blue light was used as background light. Background light may be partly necessary for sustaining the growth of filament. Negative phototropic response has not been observed.
