Abstract:
This study was conducted to determine the optimal conditions for introduction of exogenous DNA into
Synechocystis sp. PCC 6803. Of the three transformation techniques studied, electroporation, ultrasonic
transformation and natural transformation, natural transformation showed the highest efficiency. Additionally,
this study demonstrated that the higher plasmid concentration and longer homologous recombining frag ments resulted in a greater number of transformants. For successful transformation, the lowest concen tration of plasmid was 0.02 μg/ml, and the shortest homologous recombining fragment was 0.2 kb. Use of
Synechocystis sp. PCC 6803 in the logarithmic growth phase resulted in two-fold higher transformation
rate than that of the same organism when cells in the latent phase or the plateau phase were used for
transformation. Pretreatment of the host strain, Synechocystis sp. PCC 6803, with EDTA (2 mM) for two
days prior to transformation increased the transformation efficiency by 23%. Additionally, incubation of
the cells and DNA for 5 h under light conditions increased the transformation efficiency by two orders of
magnitude. Moreover, recovery treatment of the cells before they were plated onto antibiotic medium also
increased the transformation efficiency.
