Stress response and tolerance of Chlorella vulgaris to tylosin
Antibiotics are typical emerging pollutants with high ecological risk to aquatic organisms.As the primary producers of natural water,microalgae are highly susceptible to environmental changes,especially exposure to pollu-tants.However,the studies on the response of microalgae to tylosin (TYN) stress are still limited.In this study,Chlorella vulgaris,a model algae species,was selected as the experimental material to investigate the stress tolerance of microalgae exposed to TYN from the aspects of microalgal growth,physiology,metabolism,and gene expression.The results showed that TYN had a typical hormesis effect on the growth of C.vulgaris.Microalgal growth was pro-moted by low concentration of TYN (≤0.5 mg·L-1 ),with the increase of TYN exposure concentration,its inhibi-tory effect on the growth of C.vulgaris was more obvious,and it led to different degrees of oxidative damage such as cell morphological changes,plasmolysis,and thylakoid degradation.Transcriptome sequencing showed that the ex-pression levels of genes related to photosynthesis,ribosome biosynthesis,and antioxidant in C.vulgaris were signifi-cantly down-regulated after 8 days of high-concentration TYN treatment,further indicating that high-concentration TYN had an inhibitory effect on C.vulgaris cells.It was worth noting that C.vulgaris could improve the binding lev-el of TYN to functional groups such as—OH,—COOH and—NH in extracellular polymeric substance by increasing the content of extracellular polysaccharides and proteins,so as to cope with the stress effect of high concentration TYN on cells.This study systematically revealed the stress responses and tolerance of C.vulgaris to TYN,and the relevant results provided a reference for the ecological risk assessment of antibiotics in water.
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