Rhizospheric mechanisms of Bacillus subtilis bioaugmentation-assisted phytostabilization of cadmium-contaminated soil

• Published in: The Science of the total environment 2022-06, Vol.825, p.154136-154136, Article 154136
• Main Authors: Li, Qi, Xing, Yingna, Huang, Bin, Chen, Xin, Ji, Lei, Fu, Xiaowen, Li, Tianyuan, Wang, Jianing, Chen, Guanhong, Zhang, Qiang
• Format: Article
• Language: English
• Subjects: Bacillus subtilis - metabolism; Biodegradation, Environmental; Cadmium - analysis; Heavy metal; Inoculation; Lolium - metabolism; Metals, Heavy - analysis; Obstruction; Remediation; RNA, Ribosomal, 16S; Ryegrass; Soil - chemistry; Soil Pollutants - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.154136

Plant growth promoting (PGP) traits of inoculation in bioaugmentation assisted phytostabilization of heavy metal-contaminated soil have been well documented. The property of inoculation to immobilize heavy metals is another major contributor to phytostabilization efficiency. This study investigated the effects of inoculation with different concentrations of rhizobacteria Bacillus subtilis on the cadmium (Cd) bioavailability and distribution, enzyme activities, and bacterial community structure in soil planted with ryegrass (Lolium multiflorum L.). Addition of a high dosage of Bacillus subtilis decreased plant malondialdehyde (MDA) amount, increased plant antioxidant enzyme and soil nutrient cycling-involved enzyme activities, and subsequently enhanced biomass by 20.9%. In particular, the inoculation reduced the Cd bioavailability in soil, bioaccumulation coefficient (BCF), translocation factors (TF), and accumulation in ryegrass by 39.1%, 36.5%, 24.2%, and 27.9%, respectively. Furthermore, 16S rRNA gene sequencing analysis of rhizosphere soil revealed microbial community structure alterations (e.g., enrichment of Proteobacteria), eight phenotype regulations, and seventeen Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway transformations accounted for the stress mitigation and Cd immobilization in the presence of inocula. Besides, intracellular accumulation and biofilm sequestration were proposed as primary immobilization mechanisms induced by bioaugmentation. [Display omitted] •Bacillus subtilis TTL1 exhibited plant growth promoting and Cd immobilizing traits.•Inoculation stimulated enzyme activities and altered microbial community structure.•Inoculation reduced Cd bioavailability, translocation, and uptake in ryegrass.•Inoculation regulated eight phenotypes and seventeen KEGG pathways in soil microbes.•Intracellular accumulation and biofilm sequestration accounted for immobilization.