title: Biosorption mechanisms involved in immobilization of soil Pb by Bacillus subtilis DBM in a multi-metal-contaminated soil.
abstract: Mechanisms of soil Pb immobilization by Bacillus subtilis DBM, a bacterial strain isolated from a heavy-metal-contaminated soil, were investigated. Adsorption and desorption experiments with living bacterial cells as well as dead cells revealed that both extracellular adsorption and intracellular accumulation were involved in the Pb(2+) removal from the liquid phase. Of the sequestered Pb(II), 8.5% was held by physical entrapment within the cell wall, 43.3% was held by ion-exchange, 9.7% was complexed with cell surface functional groups or precipitated on the cell surface, and 38.5% was intracellularly accumulated. Complexation of Pb(2+) with carboxyl, hydroxyl, carbonyl, amido, and phosphate groups was demonstrated by Fourier transform infrared spectroscopic analysis. Precipitates of Pb5(PO4)3OH, Pb5(PO4)3Cl and Pb10(PO4)6(OH)2 that formed on the cell surface during the biosorption process were identified by X-ray diffraction analysis. Transmission electron microscopy-energy dispersive spectroscopic analysis confirmed the presence of the Pb(II) precipitates and that Pb(II) could be sequestered both extracellularly and intracellularly. Incubation with B. subtilis DBM significantly decreased the amount of the weak-acid-soluble Pb fraction in a heavy-metal-contaminated soil, resulting in a reduction in Pb bioavailability, but increased the amount of its organic-matter-bound fraction by 71%. The ability of B. subtilis DBM to reduce the bioavailability of soil Pb makes it potentially useful for bacteria-assisted phytostabilization of multi-heavy-metal-contaminated soil.
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China. Electronic address: baijunjill@gmail.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Bai
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China; Guangdong Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, China. Electronic address: eesyxh@mail.sysu.edu.cn.
authors.forename: Xiuhong
authors.initials: X
authors.lastname: Yang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Ruiying
authors.initials: R
authors.lastname: Du
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China; Guangdong Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, China.
authors.forename: Shizhong
authors.initials: S
authors.lastname: Wang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China; Guangdong Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, China.
authors.forename: Rongliang
authors.initials: R
authors.lastname: Qiu
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D007854:Lead / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D012989:Soil Pollutants / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D012989:Soil Pollutants; D007854:Lead
keywords: Bacillus subtilis DBM; Biosorption mechanisms; Immobilization; Pb speciation; Precipitation