Resistance role of Lactobacillus sp. and Lactococcus sp. to copper ions in healthy children's intestinal...

Heavy metal exposure is closely associated with gut microbe function and tolerance. However, intestinal microbe responses in children to different copper ion (Cu²⁺) concentrations have not yet been clarified. Here, in vitro cultivation systems were established for fecal microbe control and Cu²⁺-treated groups in healthy children. 16S rDNA high-throughput sequencing, meta-transcriptomics and metabolomics were used here to identify toxicity resistance mechanisms at microbiome levels. The results showed that Lactobacillus sp. and Lactococcus sp. exerted protective effects against Cu²⁺ toxicity, but these effects were limited by Cu²⁺ concentration. When the Cu²⁺ concentration was ≥ 4 mg/L, the abundance of Lactobacillus sp. and Lactococcus sp. significantly decreased, and the pathways of antioxidant activity and detoxification processes were enriched at 2 mg/L Cu²⁺, and beneficial metabolites accumulated. However, at high concentrations of Cu²⁺ (≥4 mg/L), the abundance of potential pathogen increased, and was accompanied by a downregulation of genes in metabolism and detoxification pathways, which meant that the balance of gut microbiota was disrupted and toxicity resistance decreased. From these observations, we identified some probiotics that are tolerant to heavy metal Cu²⁺, and warn that only when the concentration limit of Cu²⁺ in food is 2 mg/L, then a balanced gut microbiota can be guaranteed in children, thereby providing protection for their health.