Triclosan toxicity in a model cyanobacterium (Anabaena flos-aquae): Growth, photosynthesis and transcriptomic response

Exposure to triclosan (TCS) has been reported to reduce photosynthetic pigments, suppress photosynthesis, and inhibit growth in both prokaryotic and eukaryotic algae including An-abaena flos-aquae (a model cyanobacterium). In particular, cyanobacteria are more sensitive to TCS toxicity compared to eukaryotic algae possibly due to the structural similarity to bac -teria (target organisms); however, whether TCS exerts its toxicity to cyanobacteria by target-ing signaling pathways of fatty acid biosynthesis as in bacteria remains virtually unknown, particularly at environmental exposure levels. With the complete genome sequence of A. flos-aquae presented in this study, the transcriptomic alterations and potential toxic mech-anisms in A. flos-aquae under TCS stress were revealed. The growth, pigments and photo-synthetic activity of A. flos-aquae were markedly suppressed following a 7-day TCS exposure at 0.5 mu g/L but not 0.1 mu g/L (both concentrations applied are environmentally relevant). The transcriptomic sequencing analysis showed that signaling pathways, such as biofilm forma-tion - Pseudomonas aeruginosa, two-component system, starch and sucrose metabolism, and photosynthesis were closely related to the TCS-induced growth inhibition in the 0.5 mu g/L TCS treatment. Photosynthesis systems and potentially two-component system were iden-tified to be sensitive targets of TCS toxicity in A. flos-aquae. The present study provides novel insights on TCS toxicity at the transcriptomic level in A. flos-aquae. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.