Physiochemical responses of C. elegans under exposure to lanthanum and cerium affected by bacterial metabolism

The increasing demand for rare earth elements (REEs) in modern applications has drawn significant attention. REEs can be introduced into the environment through REE-containing fertilizers, abandoned REE-rich equipment, and mining, persisting and impacting soil quality, nutrient cycles, and plant growth. Scientists have raised concerns about REEs entering the food chain from the environment and eventually accumulating in organisms. Decades of experimental evidence have shown that these effects include inhibited growth, impaired liver function, and alterations in children's intelligence quotients. However, there exists a paucity of research that has elucidated the metabolic-level biological impacts of REEs. In our study, Caenorhabditis elegans (C. elegans) was used as a model organism to investigate physiological and inherent metabolic changes under exposure to different concentrations of REEs. The diet bacteria of nematodes play a key role in their life and development. Therefore, we investigated the influence of bacterial activity on the nematodes' response to REE exposure. We observed a concentration-dependent accumulation of REEs in nematodes, which consequently led to a reduction in lifespan and alterations in body length. Exposure to a mixed solution of REEs, in comparison to a single REE solution, resulted in greater toxicity toward nematodes. The metabolic results showed that the above changes were closely related to REE-induced amino acid metabolism disorder, membrane disturbance, DNA damage, and oxidative stress. Of note, the presence of living bacteria elicits REE effects in C. elegans. These findings highlight the potential intrinsic metabolic changes occurring in nematodes under REE exposure. Our study raises awareness of the exposure risks associated with REEs, provides valuable insight into the metabolic-level biological impacts of REEs and contributes to the development of effective mitigation strategies to reduce potential risks to human health.