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Plant uptake of cadmium (Cd) is affected by soil and environmental conditions. In this study, hydroponic experiments were conducted to investigate the effects of elevated CO 2 coupled with inoculated endophytic bacteria M002 on morphological properties, gas exchange, photosynthetic pigments, chlorophyll fluorescence, and Cd uptake of S. alfredii. The results showed that bio-fortification processes (elevated CO 2 and/or inoculated with endophytic bacteria) significantly (p < 0.05) promoted growth patterns, improved photosynthetic characteristics and increased Cd tolerance of both ecotypes of S. alfredii, as compared to normal conditions. Net photosynthetic rate (Pn) in intact leaves of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) were increased by 73.93 and 32.90%, respectively at the low Cd (2 μM), 84.41 and 57.65%, respectively at the high Cd level (10 μM). Superposition treatment increased Cd concentration in shoots and roots of HE, by 50.87 and 82.12%, respectively at the low Cd and 46.75 and 88.92%, respectively at the high Cd level. Besides, superposition treatment declined Cd transfer factor of NHE, by 0.85% at non-Cd rate, 17.22% at the low Cd and 22.26% at the high Cd level. These results indicate that elevated CO 2 coupled with endophytic bacterial inoculation may effectively improve phytoremediation efficiency of Cd-contaminated soils by hyperaccumulator, and alleviate Cd toxicity to non-hyperaccumulator ecotype of Sedum alfredii.

Inoculation with endophytic bacterium has been considered as a prospective application to improve the efficiency of phytoextraction. In this study, the effect of Buttiauxella sp. SaSR13 (SaSR13), a novel endophytic bacterium isolated from the root of hyperaccumulator Sedum alfredii, on plant growth and cadmium (Cd) accumulation in S. alfredii was investigated. Laser scanning confocal microscopic (LSCM) images showed that SaSR13 was mainly colonized in the root elongation and mature zones. The inoculation with SaSR13 to Cd-treated plants significantly enhanced plant growth (by 39 and 42% for shoot and root biomass, respectively), chlorophyll contents (by 38%), and Cd concentration in the shoot and root (by 32 and 22%, respectively). SaSR13 stimulated the development of roots (increased root length, surface area, and root tips number) due to an increase in the indole-3-acid (IAA) concentrations and a decrease in the concentrations of superoxide anion (O 2 .- ) in plants grown under Cd stress. Furthermore, inoculation with SaSR13 enhanced the release of root exudates, especially malic acid and oxalic acid, which might have facilitated the uptake of Cd by S. alfredii. It is suggested that inoculation with endophytic bacterium SaSR13 is a promising bioaugmentation method to enhance the Cd phytoextraction efficiency by S. alfredii.

Intensive agricultural system with high input of fertilizer results in high agricultural output. However, excessive fertilization in intensive agricultural system has great potential to cause nitrate and heavy metal accumulation in soil, which is adverse to human health. The main objective of the present study was to observe the effects of intercropping and inoculation of endophytic bacterium Acinetobacter calcoaceticus Sasm3 on phytoremediation of combined contaminated soil in oilseed rape (Brassica napus L.). The results showed that with Sasm3 inoculation, the biomass of rape was increased by 10-20% for shoot, 64% for root, and 23-29% for seeds while the nitrate accumulation in rape was decreased by 14% in root and by 12% in shoot. The cadmium concentration in rape increased significantly with mono-inoculating treatment, whereas it decreased significantly after intercropping treatment. By denaturing gradient gel electrophoresis (DGGE) and real-time quantitative PCR analysis, the diversity of bacterial community and the number of nirS and nirK gene copies increased significantly with inoculation or/and intercropping treatment. In conclusion, the endophytic bacterium Sasm3-inoculated intercropping system not only improved the efficiency of clearing cadmium from soil without obstructing crop production, but also improved the quality of crop.

The objective of this study was to develop a bioremediation strategy for cadmium (Cd) and carbendazim co-contaminated soil using a hyperaccumulator plant (Sedum alfredii) combined with carbendazim-degrading bacterial strains (Bacillus subtilis, Paracoccus sp., Flavobacterium and Pseudomonas sp.). A pot experiment was conducted under greenhouse conditions for 180 days with S. alfredii and/or carbendazim-degrading strains grown in soil artificially polluted with two levels of contaminants (low level, 1 mg kg(-1) Cd and 21 mg kg(-1) carbendazim; high level, 6 mg kg(-1) Cd and 117 mg kg(-1) carbendazim). Cd removal efficiencies were 32.3-35.1 % and 7.8-8.2 % for the low and high contaminant level, respectively. Inoculation with carbendazim-degrading bacterial strains significantly (P < 0.05) increased Cd removal efficiencies at the low level. The carbendazim removal efficiencies increased by 32.1-42.5 % by the association of S. alfredii with carbendazim-degrading bacterial strains, as compared to control, regardless of contaminant level. Cultivation with S. alfredii and inoculation of carbendazim-degrading bacterial strains increased soil microbial biomass, dehydrogenase activities and microbial diversities by 46.2-121.3 %, 64.2-143.4 %, and 2.4-24.7 %, respectively. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed that S. alfredii stimulated the activities of Flavobacteria and Bradyrhizobiaceae. The association of S. alfredii with carbendazim-degrading bacterial strains enhanced the degradation of carbendazim by changing microbial activity and community structure in the soil. The results demonstrated that association of S. alfredii with carbendazim-degrading bacterial strains is promising for remediation of Cd and carbendazim co-contaminated soil.