Photosynthetic and transcriptomic responses of Chlorella sp. to tigecycline

Antibiotics and other new pollutants lead to potential threat for human being. Microalgae are environmental detector because of the rapid response of microalgae against antibiotics and other pollutants in wastewater. It is essential to evaluate the physiological response and gene regulation mechanism during the wastewater treatment process containing antibiotics. The responses of growth rate, photosynthesis and transcriptome of Chlorella sp. were investigated to tigecycline (TGC). The photosynthetic activity was inhibited by 20 mg/L TGC at the beginning of the cultivation. Then, the photosynthetic activity was partially recovered from day 2. The reduction of the photosynthetic activity resulted in the decrease of growth rate under TGC condition compared with control. The transcriptomic analysis was performed for control group and TGC treatment group at day 4. Totally, 174 genes were identified as differentially expressed genes including 91 upregulated ones and 83 downregulated ones. These genes were annotated by KEGG, GO, COG, KOG, eggNOG and NR. The possible molecular mechnisms were investigated. TGC, as an antibiotic, mainly destroy protein biosynthesis in ribosome and several signal transduction pathways. Based on the transcriptomic analysis, it was shown that TGC inhibited CO₂ fixation and protein processing in endoplasmic reticulum. The up-regulation of several genes in ribosome biogenesis could be regarded as the part of tolerance mechanism of microalgae against TGC. The current study proposes new information of TGC toxicity to Chlorella sp. at both photosynthetic and transcriptomic levels.