The Effects of Tetracycline Residues on the Microbial Community Structure of Tobacco Soil in Pot Experiment

To evaluate the micro-ecological effects of tetracycline residues on tobacco soil, high-throughput sequencing technology was used to study the effects of the addition of different concentrations (0, 5, 50, and 500 mg·kg−1) of tetracycline on the abundance, diversity, and structure of bacterial and fungal communities in the rhizosphere and non-rhizosphere soil of flue-cured tobacco in China. Results showed that the presence of tetracycline had an important but varying effect on soil bacterial and fungal community richness, diversity, and structure. Changes in the diversity indices (Chao index and Shannon index) of soil bacterial and fungal communities showed a similar pattern after the addition of tetracycline; however, a few differences were found in the effects of tetracycline in the rhizosphere and non-rhizosphere soil, suggesting an evident rhizosphere-specific effect. The bacterial community at the phylum level in the rhizosphere closely clustered into one group, which might be the result of tobacco root secretions and rhizodeposition. Tetracycline showed a concentration-dependent effect on the soil bacterial community structure. The soil bacterial community structures observed after treatments with higher concentrations of tetracycline (50 and 500 mg·kg−1) were found to be closely related. Moreover, the effects of the treatments with higher concentrations of tetracycline, on the soil bacterial community at the phylum level, were different from those with lower concentrations of tetracycline (5 mg·kg−1), and CK treatments. This might have resulted from the induction of increasing selective pressure with increasing antibiotic concentration. Tetracycline continued to affect the soil bacterial community throughout the experiment. Tetracycline was found to have a varying impact on the community structure of soil fungi compared to that of soil bacteria, and the addition of an intermediate concentration of tetracycline (50 mg·kg−1) significantly increased the soil fungal diversity in the non-rhizosphere soil. The biological effects of tetracycline on the soil fungal community and the fungal-bacterial interactions, therefore, require further elucidation, warranting further research.