Repeated exposure to fungicide tebuconazole alters the degradation characteristics, soil microbial community and functional profiles

Tebuconazole is a broad-spectrum triazole fungicide that has been extensively applied in agriculture, but its toxicity on soil ecology remains unknown after repeated introduction to soil. This study investigated the degradation of tebuconazole and the changes in soil microbial community composition and functional diversity as well as network complexity in soil repeatedly treated with tebuconazole. Tebuconazole degraded slowly as the degradation half-life initially increased and then decreased during the four repeated treatments. High concentration of tebuconazole treatment significantly delayed the degradation of tebuconazole. The soil microbial functional diversity in tebuconazole-treated soils showed an inhibition-recovery-stimulation trend with increasing treatment frequency, which was related to the increased degradation rates of tebuconazole. Tebuconazole significantly decreased soil microbial biomass and bacterial community diversity, and this decreasing trend became more pronounced with increasing treatment frequency and concentration. Moreover, tebuconazole significantly decreased soil bacterial community network complexity, particularly at high concentration of tebuconazole treatment. Notably, four bacterial genera, Methylobacterium, Burkholderia, Hyphomicrobium, and Dermacoccus, were identified as the potential tebuconazole-degrading bacteria, with the relative abundances in the tebuconazole treatment significantly increasing by 42.1–34687.1% compared to the control. High concentration of tebuconazole treatment delayed increases in the relative abundances of Methylobacterium but promoted those of Burkholderia, Hyphomicrobium and Dermacoccus. Additionally, repeated tebuconazole treatments improved only four metabolic pathways, cell motility, membrane transport, environmental information processing, and xenobiotics biodegradation and metabolism, which were associated with the degradation of tebuconazole. The above results indicated that repeated tebuconazole treatments resulted in the significant accumulation of residues and long-term negative effects on soil ecology, and also emphasized the potential roles of dominant indigenous microbial bacteria in the degradation of tebuconazole.