Control of the culture conditions of Chlamydomonas reinhardtii for efficient delivery of exogenous materials in electroporation

The effects of microalgae culture conditions on the exogenous material delivery efficiency in electroporation were investigated. The exogenous material delivery into C. reinhardtii by electroporation was significantly affected by the cell growth phase state. The delivery efficiency of nucleic acid stain Yo-Pro-1 was maximized when mid log growth phase cells were used whereas the CFP transfection efficiency was maximized when late log phase cells were used. By controlling initial cell concentration and light condition, we could control cell growth and exogenous material delivery efficiency. By increasing initial cell concentration, the required time to reach mid log growth phase could be reduced but the corresponding Yo-Pro-1 delivery efficiency decreased. The diurnal light induced 20% lower saturated cell concentration than continuous light and it made positive effects on exogenous material delivery and DNA transfection. According to the present findings, it is recommended to harvest late log phase C. reinhardtii cells for more efficient transformation. The significance and implication of the present work for microalgae transformation and future work are discussed.