Ecological Toxicity Of The Chiral Fragrance Carvones On Microcystis Aeruginosa

Carvone is one of the most widely used chiral fragrances with two isomers(L-carvone and D-carvone).It imposes a potential burden on the aquatic ecosystem.However,the enantioselective toxic effects of carvone enantiomers on cyanobacterial cells remains unknown.This study aims to investigate the effects of L-and D-carvone on the physiological processes and the related gene transcription(Pho U,rbc L and mcyH)in Microcystis aeruginosa(M.aeruginosa).Carvone inhibits the growth of M.aeruginosa by down-regulating rbc L gene transcription and affecting the photosynthetic system.L-and D-carvone significantly inhibited the growth of the M.aeruginosa with the concentration and time effects.Low concentrations(1 and 2 mg/L)of D-carvone stimulated the growth of M.aeruginosa and accelerated the environmental risk of eutrophication.Carvone stimulates the activity of superoxide dismutase(SOD),catalase(CAT)and peroxidase(POD)in cells to resist oxidative damage caused by lipid peroxidation products such as malondialdehyde(MDA).Under the stimulation of L-carvone,MDA content increased and oxidative damage occurred in algae cells.Due to the consumption of M.aeruginosa growth and oxidative stress,intracellular ATP content decreased.Pho U is a negative regulator of persistent formation and phosphate metabolism in M.aeruginosa,and its transcription level was also upregulated under carvone stimulation.Meanwhile,L-carvone and D-carvone upregulated the expression of microcystic toxins(MC-LR)related gene mcy H and promoted the production and release of MC-LR.Intracellular MC-LR is more likely to leak into water under L-carvone exposure,posing a potential threat to the water environment.This may be due to cell morphological damage caused by L-carvone.The results showed that carvones had enantioselective toxicity to M.aeruginosa in physiological changes,cellular structure,oxidative damage,synthesis and release of MC-LR and gene transcription(Pho U,rbc L and mcy H).The toxicity of L-carvone was proved higher than D-carvone.The findings will also provide important insights into the toxicity effects of chiral fragrance on M.aeruginosa.It is also helpful for guiding the safe application of chiral fragrance as personal care products.