Effects of arsenic-tolerant growth-promoting bacteria on arsenic uptake and rhizosphere microbial community of hyperaccumulator Pteris vittata

Abstract:

[Objective] To analyze the effects of the addition of exogenous plant growth-promoting bacteria (PGPB) on plant growth, arsenic (As) accumulation, and rhizosphere microorganisms, and provide references for plant-microbial remediation of As-contaminated soil. [Methods] By adding exogenous PGPB into the soil, the relationships between the plant biomass and As content of Pteris vittata and the plant growth-promoting characteristics of PGPB were investigated. The high-throughput sequencing was also used to analyze the change in the rhizosphere microbial community of P. vittata with the intervention of exogenous PGPB. [Results] Two rhizobacteria Pseudomonas sp. PG12 and Bacillus sp. R19, and one endophytic bacterium P. putida S6 had typical plant growth-promoting characteristics, and the order of the growth-promoting effects on P. vittata was PG12>S6>R19. As compared with the control group, PG12, S6, and R19 increased the plant biomass by 234% (P<0.01), 136% (P<0.01), and 67%, respectively. The addition of exogenous PGPB increased the As content of P. vittata from 18.50 mg to 31.25−46.95 mg, being an increased percentage of 153% in PG12 and 139% in S6, respectively. The corresponding concentration of As in P. vittata decreased from 2 616.34 mg/kg to 1 348.04−2 156.23 mg/kg, showing a typical As “dilution effect”. Moreover, the α diversity indexes including Sobs, Chao, and Ace revealed that only R19 significantly improved the diversity of the rhizosphere microbial community, while the beta diversity analysis based on principal component analysis (PCA), principal co-ordinates analysis (PCoA), and partial least squares-discriminant analysis (PLS-DA) showed that there were significant clustering differences among all treatments. Furthermore, species composition analysis showed that the exogenous PGPB affected the distribution of the rhizosphere microbial community with an increase in the relative abundance of Arthrobacter and Solirubrobacter, etc., and a decrease in the relative abundance of Acidibacter, Dongia, and MND1. These microbial communities were presumedly associated with the growth and As uptake of P. vittata. [Conclusion] Exogenous PGPB addition shows positive effects on the growth, As uptake, and rhizosphere microbial community of P. vittata. The results of this study provide important clues for revealing the mechanism of arsenic remediation enhanced by microorganisms in plants, thereby promoting the associated studies on the plant-microbial remediation of As-contaminated soil.

Key words:plant growth-promoting bacteria;Pteris vittata;arsenic;rhizosphere microorganisms;soil remediation