Mei Wang

The impact of cadmium (Cd) and fluorine (F) on plant and human health has provoked significant public concern; however, their combined effects on plant and soil bacterial communities have yet to be determined. Here, a pot experiment was conducted to evaluate the effects of exogenous F, Cd, and their combination (FCd) on lettuce growth and soil bacterial communities. The results revealed that F and Cd concentrations in lettuce ranged from 63.69 to 219.45 mg kg⁻¹ and 1.85 to 33.08 mg kg⁻¹, respectively, presenting lower values in shoots than in the roots. Moreover, low contamination levels had no discernable influence on lettuce growth, but showed a synergistic negative on plant biomass when exogenous F and Cd exceeds 300 and 1.0 mg kg⁻¹, respectively. The results of 16S rRNA gene sequencing indicated that the most abundant bacterial community at the phylum level was Proteobacteria, with the relative abundance ranging from 33.42% to 44.10% across all the treatments. The contaminants had little effect on bacterial richness but impacted the structure of bacterial communities. The PCoA showed that compartment and contaminants were the primary contributors to the largest source of community variation, while the VPA indicated that F and Cd synergistically affected the bacterial communities. In turn, lettuce plants could enhance the resistance to the combined stress by increasing the relative abundance of Oxyphotobacteria, Subgroup 6, Thermoleophilia, and TK10 classes in the rhizosphere.

Tetracycline (TC) contamination has become hot research topic, but little attention has been paid to its ecotoxicological monitoring. The primary objective of this study is to investigate the impact of TC on human normal liver cells (HL-7702) and find indicators for monitoring their ecotoxicity. The cytotoxicity of TC, at concentrations ranging from 0 to 1000 μg L⁻¹, was assessed on HL-7702 cells. The results showed that TC significantly inhibited the cell viability at a high concentration (1000 μg L⁻¹). The TC at exposure levels ≥ 50–100 μg L⁻¹ significantly increased the levels of extracellular catalase (CAT), malondialdehyde (MDA), alanine transaminase (ALT), and aspartate transaminase (AST), and a significantly positive correlation between the TC concentrations and the values of the above parameters was observed. Swelling of the mitochondrial cristae (MC) and rough endoplasmic reticulum (RER) and the loss of ribosomes in HL-7702 cells, were observed at high TC levels. There was a positive correlation between soil TC concentration and ALT activities. The above results suggest that TC is cytotoxic to HL-7702 cells and that extracellular ALT activities can be used as a sensitive bioindicator for monitoring soil TC contamination. We, therefore, propose that the HL-7702 cell line can be a novel tool for early antibiotics toxicity monitoring.