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.

Automated summary

Exposure to TCS has been shown to inhibit growth and photosynthetic activity in cyanobacteria. This study investigated the toxic effects of TCS on Anabaena flos-aquae and identified the signaling pathways involved in the growth inhibition. The findings provide new insights into the transcriptomic responses of A. flos-aquae to TCS toxicity.