DataSheet1_Phyllosphere bacterial community and metabolomic analysis revealed the mechanism of Cd tolerance in the bryophyte Tortella tortuosa (Hedw.) Limpr.docx

IntroductionPhytoremediation 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.
MethodsIn this indoor experiment, the impacts of 40 days of Cd pollution (1 (T1), 5 (T2), 10 (T3) mg·L-1) on Cd absorption, growth and physiological characteristics, and phyllosphere bacterial diversity of Tortella tortuosa were explored.
ResultsThe results showed that the maximum Cd absorption capacity of T. tortuosa was 5.0135 mg·kg-1. The contents of leaf chlorophyll a (Chl a) and chlorophyll b (Chl b) in T. tortuosa decreased (p < 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-1). The catalase (CAT) and peroxidase (POD) activities of the T3 treatment reduced by 55% and 85%, respectively (p < 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 T. tortuosa, and positively correlated with the relative abundances of Neomycin and N-Acetyl-L-Glutamic acid.
DiscussionAlthough the severe Cd pollution could affect the physiological and metabolic characteristics of T. tortuosa, T. tortuosa 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.

引言
植物修复（Phytoremediation）是治理重金属污染这一全球性环境问题的安全绿色技术。苔藓植物（Bryophytes）以其独特的生理特性广为人知，但将其用于植物修复的相关研究却较为匮乏。

方法
本室内实验探究了40天镉（Cd）污染（设置1（T1）、5（T2）、10（T3）mg·L⁻¹三个浓度梯度）对卷叶扭口藓（Tortella tortuosa）的镉吸收能力、生长及生理特性，以及叶际（phyllosphere）细菌多样性的影响。

结果
研究结果显示，卷叶扭口藓的最大镉吸收量可达5.0135 mg·kg⁻¹。随着镉浓度升高，卷叶扭口藓的叶片叶绿素a（Chl a）与叶绿素b（Chl b）含量均显著降低（p < 0.05）。其中T3处理组的叶绿素a、b含量较对照组（CK，镉浓度为0 mg·L⁻¹）分别下降了88%与91%。T3处理组的过氧化氢酶（CAT）与过氧化物酶（POD）活性较对照组分别降低了55%与85%（p < 0.05），而丙二醛（MDA）含量较对照组升高了167%。在镉胁迫条件下，蓝细菌门（Cyanobacteria，占比63.49%）与变形菌门（Proteobacteria，占比26.62%）为优势细菌门类群。高丰度叶际细菌与卷叶扭口藓体内的镉浓度、抗氧化酶活性及叶绿素含量呈负相关，而与新霉素（Neomycin）和N-乙酰-L-谷氨酸（N-Acetyl-L-Glutamic acid）的相对丰度呈正相关。

讨论
尽管高浓度镉污染会对卷叶扭口藓的生理与代谢特性造成不利影响，但该物种对镉具备较强的吸收能力，因此可应用于重金属污染的植物修复。本研究可为土壤重金属污染修复工作提供重要参考依据。