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KMID : 0545120180280071156
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Journal of Microbiology and Biotechnology
2018 Volume.28 No. 7 p.1156 ~ p.1167
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Isolation and Characterization of Pb-Solubilizing Bacteria and Their Effects on Pb Uptake by Brassica juncea: Implications for Microbe-Assisted Phytoremediation
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Yahaghi Zahra
Shirvani Mehran
Nourbakhsh Farshid
de la Pena Teodoro Coba
Pueyo Jose J.
Talebi Majid
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Abstract
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The aim of this study was to isolate and characterize lead (Pb)-solubilizing bacteria from heavy metal-contaminated mine soils and to evaluate their inoculation effects on the growth and Pb absorption of Brassica juncea. The isolates were also evaluated for their plant growthpromoting characteristics as well as heavy metal and salt tolerance. A total of 171 Pb-tolerant isolates were identified, of which only 15 bacterial strains were able to produce clear haloes in solid medium containing PbO or PbCO3, indicating Pb solubilization. All of these 15 strains were also able to dissolve the Pb minerals in a liquid medium, which was accompanied by significant decreases in pH values of the medium. Based on 16S rRNA gene sequence analysis, the Pb-solubilizing strains belonged to genera Bacillus, Paenibacillus, Brevibacterium, and Staphylococcus. A majority of the Pb-solubilizing strains were able to produce indole acetic acid and siderophores to different extents. Two of the Pb-solubilizing isolates were able to solubilize inorganic phosphate as well. Some of the strains displayed tolerance to different heavy metals and to salt stress and were able to grow in a wide pH range. Inoculation with two selected Pb-solubilizing and plant growth-promoting strains, (i.e., Brevibacterium frigoritolerans YSP40 and Bacillus paralicheniformis YSP151) and their consortium enhanced the growth and Pb uptake of B. juncea plants grown in a metal-contaminated soil. The bacterial strains isolated in this study are promising candidates to develop novel microbe-assisted phytoremediation strategies for metal-contaminated soils.
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KEYWORD
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Metal-solubilizing bacteria, phytoremediation, Lead, contaminated soils, PGPR
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