摘要:稻米重金属污染是人们广泛关注的严重问题，微生物钝化是阻遏环境重金属进入生物循环的有效途径之一。为了解铜绿假单胞菌对苗期水稻镉污染的缓解效应，本文以无镉处理为对照，通过添加20 μmol·L-1镉的水培试验，研究了铜绿假单胞菌、载体A（硅藻土，粒径1~3 mm）、载体B（硅藻土，粒径3~6 mm）、载体C（活性炭，比表面积1 000 m2·g-1）以及铜绿假单胞菌与载体制备的菌剂A、菌剂B和菌剂C对水稻生长、镉含量及镉积累量的影响。结果表明，20 μmol·L-1镉处理显著抑制了水稻根长、株高的生长和干物质积累，添加菌液及菌剂A、B、C后，水稻生长状况得到显著改善，总生物量比镉处理（0.523 g·株-1）提高38.5%~67.3%，以菌剂B处理的水稻生物量最高。水稻根、茎鞘、叶以及地上部镉含量显著降低，其中添加菌剂A、菌剂B、菌剂C及活性炭处理的水稻地上部镉含量分别比镉处理（101.3 mg·g-1）下降45.9%、47.9%、59.9%和59.9%，迁移系数降低16.7%、25.0%、33.3%和33.3%，富集系数减少48.1%、48.8%、58.8%和60.9%。添加活性炭、菌剂A和菌剂C处理的水稻单株镉积累量降低18.2%、9.5%和24.3%，添加菌剂B以及依次含有56.4 mL、45.3 mL、28.4 mL菌悬液的菌液A、菌液B和菌液C处理，其镉积累量依次增加15.0%、30.4%、14.9%、16.9%，说明菌株通过提高作物生物量增加了镉积累。综上，铜绿假单胞菌可显著促进镉胁迫水稻的生长，降低水稻的镉含量，抑制镉的迁移，降低水稻镉的有效性；菌剂A、B、C表现出良好的镉钝化能力，表明铜绿假单胞菌可为环境镉污染的生物修复提供新菌株。
关键词:铜绿假单胞菌/
水稻/
镉/
载体/
菌剂/
微生物钝化
Abstract:Heavy metal contamination in rice is a serious problem focused by people all over the world. Microbial passivation is considered as one of effective measures to inhibit heavy metal from environmental into the biological cycle. To investigate the mitigative effects of Pseudomonas aeruginosa on rice seedling exposed to cadmium stress conditions, a set of hydroponic experiments by adding 20 μmol·L-1 cadmium solution were conducted, and the treatment without added cadmium was used as control (CK). The effects of different treatments on plant growth, cadmium content and cadmium accumulation of rice were determined. The treatments included adding with different volume of bacteria suspension, bacterial carrier A (diatomite, size 1-3 mm), carrier B (diatomite, size 3-6 mm), carrier C (activated carbon, specific surface area 1 000 m2·g-1) and microbial inoculum A, B and C, which prepared by carrier A, B and C saturated with bacteria suspension, respectively. The results showed that the growth of root length, plant height and biomass of rice were significantly inhibited by treating with 20 μmol·L-1 cadmium. But, the growth of rice was promoted by adding with P. aeruginosa suspension and microbial inoculum A, B and C. In contrast to the treatment only with cadmium (0.523 g·plant-1), total biomass of rice increased by 38.5% to 67.3%, and the highest value was tested in the treatment with inoculum B. Cadmium contents in root, stem-sheath, leaf, as well as in the above parts of rice reduced in all above treatments. Under the treatments of microbial inoculum A, B, C and activated carbon, cadmium contents in above parts of rice significantly declined by 45.9%, 47.9%, 59.9% and 59.9%, the transportation factors decreased by 16.7%, 25.0%, 33.3% and 33.3%, as well the bio-concentration factors reduced by 48.1%, 48.8%, 58.8% and 60.9%, respectively. In addition, the cadmium accumulated in rice seedling reduced by 19.2%, 9.5% and 24.3% under the treatments with activated carbon, microbial inoculum A and inoculum C, respectively. While, cadmium accumulation increased by 15.0%, 30.4%, 14.8% and 16.8% under the treatments with microbial inoculum B, bacteria suspension A, B and C, which contained 56.4 mL, 45.3 mL and 28.4 mL bacteria, respectively. It meant that the bacteria promote cadmium accumulation in rice by enlarging biomass of rice. In conclusion, P. aeruginosa exhibited the capacities of promoting rice growth, reducing cadmium content, inhibiting cadmium transportation, as well as cadmium availability of rice under cadmium stress conditions. Higher cadmium passivation abilities of microbial inoculum A, B and C in this study offer us a new promising microbial strain for bio-remediation of environmental cadmium pollution.
Key words:Pseudomonas aeruginosa/
Rice/
Cadmium/
Bacteria carrier/
Bacteria inoculum/
Microbial passivation
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