Authors: Ahmed, Iftikhar; Fujiwara, Toru

Source: Canadian Journal of Microbiology, Volume 56, Number 1, January 2010 , pp. 22-26(5)

Publisher: NRC Research Press

Abstract:

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.

Le bore (B) est toxique pour les cellules dépassé un certain seuil. Nous avons isolé plusieurs souches bactériennes tolérantes au bore (B) à partir d'échantillons de sols, et les avons étudiées quant aux mécanismes possibles de tolérance au B. Le séquençage du gène de l'ARNr 16S et une analyse phylogénique comparative ont démontré que les isolats appartiennent à six genres : Arthrobacter, Rhodococcus, Lysinibacillus, Algoriphagus, Gracilibacillus et Bacillus. Ces isolats montraient des niveaux de tolérance au B de 80, 100, 150, 300, 450 et 450 mmol/L respectivement, en maintenant une concentration intracellulaire de B significativement plus faible que celle du milieu. Une analyse statistique a montré une corrélation négative entre la concentration de B protoplasmique et le degré de tolérance au B à concentration extracellulaire élevée. Les essais cinétiques suggèrent qu'un efflux élevé et/ou une exclusion de B constituent les deux mécanismes responsables de la tolérance à concentration externe de B élevée.

Document Type: Research article

Publication date: 2010-01-01

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• Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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