Effects of polyester microfibers (PMFs) and cadmium on lettuce (Lactuca sativa) and the rhizospheric microbial communities: A study involving physio-biochemical properties and metabolomic profiles

Microfibers (MFs) and cadmium (Cd) are widely distributed in soil ecosystems, posing a potential threat to soil biota. To explore potential risks of single MFs and in combination with Cd (co-PMFs/Cd) to soil environment, we systematically investigated the effects of PMFs and co-PMFs/Cd treatments on physio-biochemical performance and metabolomic profile of lettuce (Lactuca sativa), as well as the rhizospheric bacterial communities. Our results showed that both PMFs and co-PMFs/Cd treatments adversely disturbed the plant shoot length, photosynthetic, and chlorophyll content. Co-PMFs/Cd specifically increased the activities of antioxidant enzymes. The metabolites in lettuce leaf were significantly altered by PMFs and co-PMFs/Cd treatments. A significant reduction in the relative abundance of amino acids sugar and sugar alcohols indicated the altered nitrogen and carbohydrates related metabolic pathways. Additionally, PMFs and co-PMFs/Cd treatments altered the structure of rhizospheric bacterial communities and caused significant changes in some key beneficial/functional bacteria involved in the C, and N cycles. The present study provides a novel insight into the potential effects of PMFs on plant and rhizosphere bacterial communities and highlights that PMFs can threaten the terrestrial ecosystem and should be further explored in future research.