Mercury Tolerance of Thermophilic <Emphasis Type="Italic">Bacillus</Emphasis> sp. and <Emphasis Type="Italic">Ureibacillus</Emphasis> sp |
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Authors: | K?J?Glendinning Email author" target="_blank">L?E?MacaskieEmail author N?L?Brown |
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Institution: | (1) School of Biosciences, The University of Birmingham, B15 2TT Edgbaston, Birmingham, UK |
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Abstract: | Although resistance of microorganisms to Hg(II) salts has been widely investigated and resistant strains have been reported
from many eubacterial genera, there are few reports of mercuric ion resistance in extremophilic microorganisms. Moderately
thermophilic mercury resistant bacteria were selected by growth at 62 °C on Luria agar containing HgCl2. Sequence analysis of 16S rRNA genes of two isolates showed the closest matches to be with Bacillus pallidus and Ureibacillus thermosphaericus. Minimum inhibitory concentration (MIC) values for HgCl2 were 80 μg/ml and 30 μg/ml for these isolates, respectively, compared to 10 μg/ml for B. pallidus H12 DSM3670, a mercury-sensitive control. The best-characterised mercury-resistant Bacillus strain, B. cereus RC607, had an MIC of 60 μg/ml. The new isolates had negligible mercuric reductase activity but removed Hg from the medium
by the formation of a black precipitate, identified as HgS by X-ray powder diffraction analysis. No volatile H2S was detected in the headspace of cultures in the absence or presence of Hg2+, and it is suggested that a new mechanism of Hg tolerance, based on the production of non-volatile thiol species, may have
potential for decontamination of solutions containing Hg2+ without production of toxic volatile H2S. |
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Keywords: | Bacillus sp mercury resistance thermophilic bacilli Ureibacillus sp |
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