Evaluation of Shifts of Gene Transcription Levels of Unicellular Green Alga Due to UV-C Irradiation.

Green algae produce valuable lipids as carbon-recycling resources. Collecting whole cells with the intracellular lipids could be efficient without cell burst; however, direct use of the cells causes microbial contamination in environments. Then, UV-C irradiation was selected to satisfy the requirements of avoiding the cell burst and sterilizing cells with . UV-C irradiation with 1.209 mW·cm showed enough sterilization activity for 1.6 × 10 cells·mL of in a depth of 5 mm for 10 min. The irradiation showed no effects to composition and contents of the intracellular lipids. From the viewpoint of transcriptomic analysis, the irradiation displayed possibilities of (i) inhibition of the synthesis of lipids due to decrement of the transcription of related genes, such as and , and (ii) activation of lipid degradation and the production of NADH and FADH due to increment of the transcription of related genes, such as , and . Irradiation until cell death could be insufficient to shift the metabolic flows even though the transcriptions were already shifted to lipid degradation and energy production. This paper is the first report of the response of to UV-C irradiation on the transcription level.