• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.1992-1998
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• 2018

In 2015, Bacillus paralicheniformis was separated from B. licheniformis on the basis of phylogenomic and phylogenetic studies, and urease activity was reported as a phenotypic property that differentiates between the two species. Subsequently, we have found that the urease activity of B. paralicheniformis is strain-specific, and does not reliably discriminate between species, as strains having the same urease gene cluster were identified in B. licheniformis and B. sonorensis, the closest relatives of B. paralicheniformis. We developed a multilocus sequence typing scheme using eight housekeeping genes, adk, ccpA, glpF, gmk, ilvD, pur, spo0A, and tpi to clearly identify B. paralicheniformis from closely related Bacillus species and to find a molecular marker for the rapid identification of B. paralicheniformis. The scheme differentiated 33 B. paralicheniformis strains from 90 strains formerly identified as B. licheniformis. Among the eight housekeeping genes, spo0A possesses appropriate polymorphic sites for the design of a B. paralichenofomis-specific PCR primer set. The primer set designed in this study perfectly separated B. paralicheniformis from B. licheniformis and B. sonorensis.

• Journal of Microbiology and Biotechnology
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• v.28 no.7
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• pp.1156-1167
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• 2018

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 growth-promoting 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 $PbCO_3$, 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.