Co-occurrence patterns of microbial communities affected by inoculants of plant growth-promoting bacteria during phytoremediation of heavy metal-contaminated soils.

Phytoremediation assisted by plant growth-promoting bacteria (PGPB) is an alternative method of cleaning up toxic metals from soil. However, the interactions among indigenous soil microorganisms following PGPB inoculation are far from fully understood, although these interactions are conducive to evaluate the effectiveness of PGPB. Here, we used Illumina Miseq sequencing and network analysis to decipher the co-occurrence patterns of bacterial communities following PGPB inoculation during phytoremediation of heavy metal contaminated soil. Miseq sequencing revealed that PGPB inoculation changed the bacterial community composition one day after inoculation, with minor changes continuing to be observed ten days after inoculation. This suggested that PGPB inoculants did not proliferate extensively in a new environment. Network analysis showed that PGPB inoculation altered the co-occurrence patterns, dominant modules and topological roles of individual OTUs. In the presence of PGPB inoculants the bacterial community had more complex and compact associations. Moreover, PGPB inoculation increased the percentage of connectors, indicating that PGPB may contribute to more intensified interactions among OTUs from different modules; consequently, the microbial community would be more ordered and efficient. The enhanced co-occurrence associations in the PGPB-inoculated bacterial network may contribute to the plant growth-promoting effects of PGPB during phytoremediation of heavy metal-contaminated soil.

Kong Z ，Wu Z ，Glick BR ，He S ，Huang C ，Wu L ... -  《-》

Inoculation of plant growth promoting bacteria from hyperaccumulator facilitated non-host root development and provided promising agents for elevated phytoremediation efficiency.

Plant growth promoting bacteria (PGPB) have been reported to have the ability to promote plant growth, development and increase heavy metals (HMs) uptake. Therefore, PGPB inoculation as soil remediation agents into plants with larger biomass and potential of phytoextraction is of great importance to increase bioremediation efficiency. In this study, 12 PGPB strains isolated from a cadmium (Cd)/zinc hyperaccumulator Sedum alfredii Hance were inoculated into non-host plant Brassica juncea and their effects on plant growth and Cd uptake were determined. The results showed that inoculation of most PGPB strains promoted plant growth, boosted root development and improved chlorophyll content in the absence of Cd. Inoculation of PGPB strains promoted plant growth up to 111% in shoot and 358% in root when treated with 2 μM Cd. In addition, PGPB inoculation not only ameliorated plant root morphology including the total root length (RL), total surface area (SA), total root volume (RV) and number of root tips (RT), but also facilitated Cd uptake up to 126%. Furthermore, inoculation of PGPB strains promoted plant Cd accumulation up to 261% in shoot and up to 8.93-fold increase in root. Among all the 12 PGPB strains, Burkholdria SaMR10 and Sphingomonas SaMR12 were identified as the promising microbes for improving phytoremediation efficiency of Cd contaminated soils. These results not only provided useful findings for further investigation of interacting mechanisms between different bacterial strains and plants, but also facilitated the development of microbe-assisted phytoremediation application for HM contaminated soil.

Wang Q ，Ma L ，Zhou Q ，Chen B ，Zhang X ，Wu Y ，Pan F ，Huang L ，Yang X ，Feng Y ... -  《-》

The Role of Plant Growth-Promoting Bacteria in Metal Phytoremediation.

Phytoremediation is a promising technology that uses plants and their associated microbes to clean up contaminants from the environment. In recent years, phytoremediation assisted by plant growth-promoting bacteria (PGPB) has been highly touted for cleaning up toxic metals from soil. PGPB include rhizospheric bacteria, endophytic bacteria and the bacteria that facilitate phytoremediation by other means. This review provides information about the traits and mechanisms possessed by PGPB that improve plant metal tolerance and growth, and illustrate mechanisms responsible for plant metal accumulation/translocation in plants. Several recent examples of phytoremediation of metals facilitated by PGPB are reviewed. Although many encouraging results have been reported in the past years, there have also been numerous challenges encountered in phytoremediation in the field. To implement PGPB-assisted phytoremediation of metals in the natural environment, there is also a need to critically assess the ecological effects of PGPB, especially for those nonnative bacteria.

Kong Z ，Glick BR 《-》

Isolation, characterization and the effect of indigenous heavy metal-resistant plant growth-promoting bacteria on sorghum grown in acid mine drainage polluted soils.

Wu Z ，Kong Z ，Lu S ，Huang C ，Huang S ，He Y ，Wu L ... -  《-》

Phytoremediation effect of Scirpus triqueter inoculated plant-growth-promoting bacteria (PGPB) on different fractions of pyrene and Ni in co-contaminated soils.

At present, few reveal the mechanism of inoculation plants with PGPB to remediate PAH-metal co-contaminated soil by analyzing the chemical speciations of contaminants. This study investigated the influence of inoculation plants with PGPB on different fractions of pyrene and Ni in rhizospheric and non-rhizospheric soil. The results demonstrated that the addition of PGPB brought the extensive increase of FDA activities in pyrene-Ni co-contaminated soil. PGPB increased the resistance of plants in nickel and pyrene-Ni contaminated soil, but decreased the plant biomass in single pyrene contaminated soil. The addition of PGPB efficiently decreased bioaccessible fractions of pyrene and increased the bioavailability of Ni in both rhizospheric and non-rhizospheric soil. Although inoculation plants with PGPB significantly increased the accumulation of Ni in single Ni and pyrene-Ni co-contaminated soil, the poor bioavailability of Ni in rhizospheric soil still restricted the phytoremediation of the heavy metal. The presence of pyrene hindered the inoculated plant from accumulating Ni to some extent. On the contrary, the presence of Ni significantly promoted the degradation of pyrene in both rhizospheric and non-rhizospheric soil after inoculation plants with PGPB.

Chen X ，Liu X ，Zhang X ，Cao L ，Hu X ... -  《-》