Ferrous amendment alters rice uptake of tetracyclines and bacterial community compositions in paddy soils.

Tetracyclines (TCs) residues in agricultural soils pose significant threats to crop safety and human health. Ferrous (Fe(II)) amendment is a promising strategy for contaminated soil remediation. However, the effects of Fe(II) on the fate of TCs in paddy soil remain unexplored. This study investigated (i) the effect of Fe(II) on the bioaccumulation and translocation of TCs (oxytetracycline, doxycycline, tetracycline, and chlortetracycline) in rice tissues and (ii) bacterial community shifts in rhizosphere and bulk soils. TCs residues in paddy soil showed a positive correlation with the initial exposure dosage. Fe(II) amendment promoted the formation of iron plaque on root surfaces, which retained approximately 50-70 % of TCs, thereby reducing TCs residues and restricting their further upward translocation as a physical barrier. TCs exposure induced phytotoxicity in rice, while Fe(II) supplement alleviated TCs-induced oxidative damage in rice plants. Moreover, TCs exposure and Fe(II) supplement reshaped bacterial community composition, resulting in a predominance of Proteobacteria and Gemmatimonadota. The enrichment of TCs degrader and iron-oxidizing bacteria in the rhizosphere promoted the reduction of TCs residues in soil and their accumulation on root surfaces. Collectively, Fe(II) amendment is a promising approach to reduce antibiotic residues in paddy soil and hence rice.