Characterization of boron resistant and accumulating bacteria Lysinibacillus fusiformis Ml, Bacillus cereus M2, Bacillus cereus M3, Bacillus pumilus M4 isolated from former mining site, Hokkaido, Japan

摘要

Boron is known to be widespread environmental contaminant that is relatively mobile in soil when compared to other metal contaminants. The present study made an attempt to isolate and characterize the boron resistant and accumulating bacteria from former mining site at Hokkaido, Japan. Four potential strains Ml, M2, M3 and M4 were selected based on high degree of boron and heavy metal resistances. The morphological, biochemical and 16S rDNA sequencing analysis of mining bacteria revealed that the isolates were highly homology to Lysinibacillus fusiformis Ml (99 %), Bacillus cereus M2 (99 %), Bacillus cereus M3 (99 %) and Bacillus pumilus M4 (99 %) respectively. The strains Ml, M2, M3 and M4 showed resistance to several heavy metals such as As (Ⅲ), As (Ⅴ) and Cr (Ⅵ), Cu, Ni, Pb and Zn. The selected strains were found to be arsenic oxidizing bacteria confirmed by Silver nitrate test. The resting and growing cells of mining bacteria were used for boron accumulation analysis. Selected strains were found to be efficiently accumulating boron concentration ranging from 0.1-2.3 mg L-1 and 1.5-4.7 mg L-1at 24 h and 168 h, respectively. The following results conclude that the mining bacteria act as potent bioaccumulator of boron and its resistant, removal characteristic can be valuable in boron bioremediation.