Core bacteria carrying the genes associated with the degradation of atrazine in different soils.

Atrazine residues can pose serious threats to soil ecology and human health. Currently, the underlying relationship between soil microbial communities and the degradation genes associated with atrazine degradation remains unclear. In this study, the degradation characteristics of atrazine was investigated in ten different soil types. Further, diversity and abundance of degradation genes and succession of the bacterial community were also studied. The degradation of 10 mg/kg atrazine in different soil types exhibited an initial rapid trend followed by a gradual slowdown, adhering to the first-order kinetic equation. Atrazine significantly increased the absolute abundance of atz degradation genes. The increase in the absolute abundance of atzC gene was the largest, whereas that of atzA gene was the smallest, and the trzD gene was only detected in the Binzhou loam soil. Co-occurrence network analysis showed that the number of potential bacterial hosts of atzC was the highest compared with the other atz genes. Atrazine also altered the structural composition of the soil microbial community. The relative abundances of Ochrobactrum, Nocardiopsis, Lactobacillus, and Brevibacterium was increased in the atrazine-treated soils, while those of Conexibate, Solirubacter, and Micromonospora was decreased significantly compared with the control. Additionally, four atrazine-degrading bacterial strains Rhizobium AT1, Stenotrophomonas AT2, Brevibacterium AT3, and Bacillus AT4 were isolated from the atrazine-treated soils. After 14 d for inoculation, their degradation rate for 10 mg/L atrazine ranged from 17.56 % to 30.55 %. Moreover, the relative abundances of the bacterial genera, including these four isolates, in the atrazine-treated soil were significantly higher than those in the control, indicating that they were involved in the synergistic degradation of atrazine in the soil. This study revealed the degradation characteristics of atrazine, distribution of degradation genes, and succession of microbial communities, and explored the internal relationship between microbial community structure and atrazine degradation mechanisms in different soil types.