Indigenous Bacteria Have High Potential for Promoting Salix integra Thunb. Remediation of Lead-Contaminated Soil by Adjusting Soil Properties

Abstract

Salix integra Thunb., a fast-growing woody plant species, has been used for phytoremediation in recent years. However, little knowledge is available regarding indigenous soil microbial communities associated with the S. integra phytoextraction process. In this study, we used an Illumina MiSeq platform to explore the indigenous microbial composition after planting S. integra at different lead (Pb) contamination levels: no Pb, low Pb treatment (Pb 500 mg kg −1 ), and high Pb treatment (Pb 1500 mg kg −1 ). At the same time, the soil properties and their relationship with the bacterial communities were analyzed. The results showed that Pb concentration was highest in the root reaching at 3159.92 ± 138.98 mg kg −1 under the high Pb treatment. Planting S. integra decreased the total Pb concentration by 84.61 and 29.24 mg kg −1 , and increased the acid-soluble Pb proportion by 1.0 and 0.75% in the rhizosphere and bulk soil under the low Pb treatment compared with unplanted soil, respectively. However, it occurred only in the rhizosphere soil under the high Pb treatment. The bacterial community structure and microbial metabolism were related to Pb contamination levels and planting of S. integra, while the bacterial diversity was only affected by Pb contamination levels. The dominant microbial species were similar, but their relative abundance shifted in different treatments. Most of the specific bacterial assemblages whose relative abundances were promoted by root activity and/or Pb contamination were suitable for use in plant-microbial combination remediation, especially many genera coming from Proteobacteria. Redundancy analysis (RDA) showed available nitrogen and pH having a significant effect on the bacteria relating to phytoremediation. The results indicated that indigenous bacteria have great potential in the application of combined S. integra-microbe remediation of lead-contaminated soil by adjusting soil properties.

Assessment of rhizosphere bacterial diversity and composition in a metal hyperaccumulator (Boehmeria nivea) and a nonaccumulator (Artemisia annua) in an antimony mine

“…Bacteria possess many adaptations to detoxify metals via biosorption, bioaccumulation, biotransformation and biomineralization (Banach et al, 2020). The relative abundance of bacteria in the rhizosphere resulted from the co‐selection of specific plant root activity and soil heavy metal pollution (Hou et al, 2018; Niu et al, 2020). These bacteria with higher abundance (such as Acidobacteria and Bacteroidetes ) can improve the enrichment ability and growth ability of hyperaccumulators in a heavy metal environment.…”

“…In this area, B. nivea and A. annua have a wide distribution. Some studies have confirmed that B. nivea is a heavy metal hyperaccumulator (Bai et al, 2021;Chai et al, 2016;Pan et al, 2019;Sun et al, 2014;Wang et al, 2018;Wei et al, 2015;Yang et al, 2010;Zhou et al, 2010) and A. annua is a nonaccumulator (Bai et al, 2021;Deng et al, 2016;Huang et al, 2014).…”

“…Excessive concentration of toxic metals (oid) cause serious toxicity for the growth and development of most living organisms (Tchounwou et al, 2012). Some plants growing in toxic metals (oid) contaminated soils have high tolerances to heavy metal toxicity in the growth matrix (Huang et al, 2014;Pan et al, 2019;Verbruggen et al, 2009). In this case, plants show high tolerance through two opposing mechanisms.…”

“…On the one hand, some hyperaccumulators have evolved a special ability to accumulate higher concentrations of metal in their aboveground parts, compared to nonaccumulator plants in the same environment (Van der Ent et al, 2013). For example, Cd-hyperaccumulator Boehmeria nivea showed a high accumulation of Cd in its shoots and roots (490.3 and 157.2 mg kg −1 , respectively) and a high translocation factor (92.0) (Pan et al, 2019). On the other hand, some tolerant plants (nonaccumulators) can exclude toxic metals from absorption, thus limiting metal entry and transfer from root to stem to physiological concentrations (Verbruggen et al, 2009).…”

Inoculation With Indigenous Rhizosphere Microbes Enhances Aboveground Accumulation of Lead in Salix integra Thunb. by Improving Transport Coefficients

“…Roots, shoots, and leaves of each sample were oven-dried at 80°C for 24 h, and then dry biomass was measured. Roots, shoots, and leaves were ground and passed through a 60-mesh sieve to measure total Pb content following the method described by Niu et al (2020) .…”