Biodegradation of the Fungicide Picoxystrobin by <i>Hyphomicrobium</i> sp. H-9 and Detoxification Mechanism as Indicated by the Microalgae <i>Tetradesmus obliquus</i>

Picoxystrobin is widely used in agriculture, causing residual contamination of habitats and ecotoxicity. In this study, a picoxystrobin-degrading strain H-9 was isolated and identified as <i>Hyphomicrobium</i> sp. It can rapidly degrade four strobilurin fungicides (picoxystrobin, trifloxystrobin, azoxystrobin, and kresoxim-methyl) to produce the corresponding SF acids and methanol via the hydrolysis of ester bonds. Picoxystrobin can significantly inhibit the growth of algal cells and the synthesis of chlorophyll in <i>Tetradesmus obliquus</i>. The detoxification capacity of strain H-9 was evident as it mitigated picoxystrobin-induced growth inhibition and oxidative stress in <i>T. obliquus</i>. Strain H-9 modulated the expression of genes involved in photosynthesis, the Calvin cycle, the tricarboxylic acid cycle, glycolysis, oxidative stress, and chlorophyll synthesis, thereby alleviating picoxystrobin toxicity to <i>T. obliquus</i>. This study enhances our understanding of the detoxification mechanism of microorganisms on microalgae exposed to SF stress and provides a novel insight into the microbial remediation of SFs-contaminated environments.