Mechanism of boron tolerance in soil bacteria.
Boron (B) is toxic to living cells at levels above a certain threshold. We isolated several B-tolerant bacterial strains from soil samples and studied them for possible mechanisms of B tolerance. 16S rRNA gene sequencing and comparative phylogenetic analysis demonstrated that the isolates belong to the following 6 genera: Arthrobacter, Rhodococcus, Lysinibacillus, Algoriphagus, Gracilibacillus, and Bacillus. These isolates exhibited B-tolerance levels of 80, 100, 150, 300, 450, and 450 mmol/L, respectively, whilst maintaining a significantly lower intracellular B concentration than in the medium. Statistical analysis showed a negative correlation between the protoplasmic B concentration and the degree of tolerance to a high external B concentration. The kinetic assays suggest that the high B efflux and (or) exclusion are the tolerance mechanisms against a high external B concentration in the isolated bacteria.
Plant Biotechnology Program, Institute of Agricultural Biotechnology and Genetic Resources, National Agricultural Research Centre, Park Road, Islamabad 45500, Pakistan. iftikharnarc@hotmail.com
Iftikhar
I
Ahmed
Toru
T
Fujiwara
D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015373:Bacterial Typing Techniques; D001895:Boron / Q000378:metabolism* / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D004351:Drug Resistance / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism* / Q000494:pharmacology*
D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; D001895:Boron