Effect of Salinity on the Tolerance to Toxic Metals and Oxyanions in Native Moderately Halophilic Spore-forming Bacilli |
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Authors: | M A Amoozegar J Hamedi M Dadashipour S Shariatpanahi |
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Institution: | (1) Department of Biology, Faculty of Science, University of Tehran, Tehran, Iran;(2) Department of Biochemistry, Pasteur Institute of Iran, Tehran, 13164, Iran |
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Abstract: | Summary Ten moderately halophilic spore-forming bacilli were isolated from saline soils in Iran and their intrinsic high-level resistance
to chromate, arsenate, tellurite, selenite, selenate and biselenite was identified by an agar dilution method. Minimum inhibitory
concentration (MIC) for each oxyanion was determined. All isolates were resistant to higher concentrations of arsenate. The
resistance level of the isolates to selenooxyanions was between 10 and 40 mM. Maximum and minimum tolerance against oxyanions
was seen in selenite and biselenite, respectively. Although toxic metal resistance in the isolates was not different from
non-halophilic bacteria that has been reported, unusual resistance to arsenate (250 mM), sodium chromate (75 mM) and potassium
chromate (70 mM) was observed. The results obtained in this study revealed that all isolates were obviously susceptible to
silver, nickel, zinc and cobalt, while seven isolates were resistant to lead. Susceptibility to copper and cadmium varied
among the isolates. Silver had the maximum toxicity, whereas lead and copper showed minimum toxicity. The impact of salinity
on the toxicity of oxyanions was also studied. Our results showed that in general an increase in salinity from 5% (w/v) to
15% (w/v) enhanced tolerance to toxic oxyanions. |
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Keywords: | Chromate halophilic bacteria oxyanions selenite tellurite tolerance toxic metal |
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