Abstract

Although many factors that affect the frequency of natural transformation of the unicellular cyanobacterium Synechocystis have been extensively reported, little is known regarding the effects of changes in the spectral quality and intensity of light on its natural transformation. The frequency of natural transformation was significantly enhanced or inhibited by the treatments with low light (LL) or high light (HL) under the incubation condition of cells and DNA before plating and/or on the plates in comparison with that by the treatment with growth light (GL); the changes in the spectral quality of light did not remarkably affect the transformation efficiency of Synechocystis. Further, the lengths of the appearance time of transformants were shortened or retarded by HL or LL illumination when cells and DNA were incubated on the plates relative to that by GL illumination. Further, the transformation efficiency of Synechocystis was closely associated with the permeability of the cell membranes. Treatment with LL significantly enhances the frequency of natural transformation whereas HL illumination remarkably shortens the appearance time of Synechocystis transformants. These phenomena can be extensively applied to future studies according to the specific demands of the transformation experiments. Possible mechanisms underlying these phenomena are discussed.

Key words: Appearance time of transformants, light treatments, natural transformation,Synechocystis, transformation efficiency.