Phyllosphere bacterial community and metabolomic analysis revealed the mechanism of Cd tolerance in the bryophyte (Hedw.) Limpr.

Introduction: Phytoremediation is a safe and green technology for the remediation of heavy metal pollution, a global environmental problem. Bryophytes are well known for their special physiological properties, but there is little research on the use of bryophytes for phytoremediation.

Methods: In this indoor experiment, the impacts of 40 days of Cd pollution (1 (T1), 5 (T2), 10 (T3) mg·L) on Cd absorption, growth and physiological characteristics, and phyllosphere bacterial diversity of were explored.

Results: The results showed that the maximum Cd absorption capacity of was 5.0135 mg·kg. The contents of leaf chlorophyll a () and chlorophyll b () in decreased ( < 0.05) with the increase of Cd concentration. Especially, the Chl a and Chl b contents of the T3 treatment reduced by 88% and 91%, respectively compared with those of the CK (Cd: 0 mg·L). The catalase (CAT) and peroxidase (POD) activities of the T3 treatment reduced by 55% and 85%, respectively ( < 0.05), and the malondialdehyde (MDA) content increased by 167%, compared with those of the CK. Under Cd exposure, Cyanobacteria (63.49%) and Proteobacteria (26.62%) were the dominant bacterial phyla. The highly abundant phyllosphere bacteria were negatively correlated with the Cd concentration, antioxidant enzyme activity, and chlorophyll content in , and positively correlated with the relative abundances of Neomycin and N-Acetyl-L-Glutamic acid.

Discussion: Although the severe Cd pollution could affect the physiological and metabolic characteristics of , had a strong absorption capacity for Cd. Therefore, it could be used for phytoremediation of heavy metal pollution. This study will provide a reference for the remediation of soil heavy metal pollution.