The combined effects of tetracycline and glyphosate on growth and rhizosphere bacteria community in hulless barley over the whole growth period

Date:12-02-2024

Highlights

• A low concentration (1 mg/kg) of TC exhibited an antagonistic relationship with Gly.

• Higher concentrations of TC (2.5-10 mg/kg) demonstrated a synergistic relationship with Gly.

• Proteobacteria and Actinobacteria were predominant at the tillering and jointing stages.

• Barley-associated soils were primarily colonized by Acidobacteria at the ripening stage.

• P450-associated bacteria is vital in chemical metabolism during the ripening stage.

Abstract

The toxic effects of tetracycline and glyphosate on hulless barley and its environment, as well as their interrelationship, remain poorly understood. The present study aimed to identify biomarkers reflective of tetracycline and glyphosate toxicity, examine root damage and rhizosphere bacterial communities throughout the growth cycle, and assess the final grain quality. 

Results indicated that the hydrogen peroxide (H₂O₂) content in the underground parts of barley could serve as a sensitive biomarker for detecting tetracycline and glyphosate toxicity in barley. In addition, a synergistic effect between 5 mg/kg tetracycline and 5 mg/kg glyphosate was observed at the tillering stage, which not only induced H₂O₂ accumulation across all growth stages but also ultimately reduced seed quality. During the tillering phase, Proteobacteria dominanted, while Actinobacteria showed greater relative abundance during the jointing stage. By the ripening stage, Acidobacteria predominantly colonized the associated soils. 

Importantly, the study further identified metagenome-assembled genomes containing cytochrome P450 fragments capable of metabolizing these compounds. This study provides novel insights into the transformation of co-contaminants and the adaptive responses of rhizobacteria to tetracycline and glyphosate exposure, offering valuable information for agricultural practices.

Graphical abstract

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