Inhibition of Motility in the Cyanobacterium, Phormidium uncinatum, by Solar and Monochromatic UV Irradiation

The effect of solar radiation and monochromatic UV radiationon the motility of the filamentous cyanobacterium Phormidiumuncinatum was determined. Solar radiation (mid-day, in midsummerat a location near Lisboa, Portugal) was found to impair motilitywithin about 30 min. This effect is neither a result of a temperatureincrease nor of visible light. The spectral sensitivity determinedusing the Okazaki Largé Spectrograph shows the maximaleffectiveness of radiation of 300 nm. The short time requirementfor the response and the lack of any photoreactivation of motilityargues against DNA being the UV target. Investigations usingreagents diagnostic of superoxide free radicals and singletoxygen failed to confirm the involvement of photodynamic effectsas the molecular mechanism causing UV inhibition of motility. ³Present address: Biology Department, Faculty of Science, Universityof Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan (Received March 15, 1986; Accepted April 25, 1986)