产酸内生菌荧光假单胞菌R1对东南景天生长和吸收、积累土壤中重金属锌镉的影响

研究了从东南景天（Sedum alfredii）的根系分离和纯化的内生菌荧光假单胞菌（Pseudomonas fluorescens）R1（菌株R1）在溶解氧化锌（ZnO）和氧化镉（CdO）过程中的生长代谢特征，分析了代谢产物中有机酸的组成及含量；通过盆栽实验，进一步探讨了土壤接种菌株R1对东南景天的生长、吸收和积累锌、镉的影响。结果发现，菌株R1在生长代谢过程中分泌苹果酸、琥珀酸、乙酸、柠檬酸、草酸等有机酸是导致ZnO和CdO溶解的主要原因，且反应体系中增加ZnO和CdO能够提高有机酸的分泌量，加速ZnO和CdO的溶解。菌株R1接种到未灭菌或灭菌的锌、镉污染土壤中均能在一定程度上促进东南景天的生长和吸收Zn、Cd。在未灭菌ZnO土壤上，接种菌株R1使东南景天根系和地上部的干物质质量、地上部Zn积累量分别增加了15.56%、9.74%和29.84%；在灭菌ZnO土壤上，接种菌株R1使东南景天地上部的干物质质量和Zn积累量分别增加9.56%和8.97%。在未灭菌CdO土壤上，接种菌株R1使东南景天根系和地上部的干物质质量、地上部Cd积累量分别增加30.30%、6.15%和27.21%；在灭菌CdO土壤上，接种菌株R1使东南景天根系和地上部的干物质质量、地上部Cd积累量分别增加5.08%、8.82%和26.14%。

Effects of acid producing endophytic bacteria Pseudomonas fluorescens R1 on the growth responses,Zn and Cd accumulation in Sedum alfredii

Endophytic bacteria Pseudomonas fluorescens R1 were isolated from the root of Zn/Cd-hyperaccumulator Sedum alfredii, and their metabolic characteristics during the ZnO and CdO dissolution process and the composition and content of organic acids in the metabolites were studied. Batch series of pot experiments were conducted to evaluate the effects of these endophytic bacteria on the growth and accumulation of Zn and Cd in S. alfredii. Malic acid, succinic acid, acetic acid, citric acid, and oxalic acid produced during the metabolic process of P. fluorescens R1 enhanced the dissolution of ZnO and CdO, and vice versa, i.e., the addition of ZnO or CdO to the reaction system increased the secretion of organic acids. Irrespective of the non-sterile or sterile soil treatments, the inoculation of P. fluorescens R1 into the ZnO and CdO-contaminated soil enhanced plant growth and accumulation of Zn and Cd compared to the absence of inoculation. In the S. alfredii group grown in non-sterile soil subjected to ZnO treatment and inoculation with P. fluorescens R1, the dry weight of roots and shoots and the total Zn accumulation in shoots increased by 15.56%, 9.74%, and 29.84%, respectively. For groups grown in ZnO-treated and P. fluorescens R1-inoculated sterile soil, the dry weight of shoots and the total Zn accumulation in shoots of S. alfredii increased by 9.56% and 8.97%, respectively. Similarly, for S. alfredii grown in soils subjected to CdO treatment and P. fluorescens R1 inoculation, the dry weight of roots and shoots and the total Cd accumulation in shoots increased by 30.30%, 6.15%, and 27.21% (non-sterile soil) and 5.08%, 8.82%, and 26.14% (sterile soil), respectively.