Mercury resistance and volatilization by oil utilizing haloarchaea under hypersaline conditions
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The hydrocarbon utilizing haloarchaea, Haloferax (two strains), Halobacterium and Halococcus from a hypersaline coastal area of the Arabian Gulf, had the potential for resistance and volatilization of Hg2+. Individual haloarchaea resisted up to between 100 and 200 ppm HgCl2 in hydrocarbon free media with salinities between 1 and 4 M NaCl, but only up to between 20 and 30 ppm in a mineral medium containing 3 M NaCl, with 0.5% (w/v) crude oil, as a sole source of carbon and energy. Halococcus and Halobacterium volatilized more mercury than Haloferax. The individual haloarchaea consumed more crude oil in the presence of 3 M NaCl than in the presence of 2 M NaCl. At both salinities, increasing the HgCl2 concentration in the medium from 0 to 20 ppm resulted in decreasing the oil consumption values by the individual haloarchaea. However, satisfactory oil consumption still occurred in the presence of 10 ppm HgCl2. It was concluded that haloarchaea with the combined potential for mercury resistance and volatilization and hydrocarbon consumption could be useful in removing toxic mercury forms effectively from oil free, mercury contaminated, hypersaline environments, and mercury and oil, albeit less effectively, from oily hypersaline environments.
KeywordsCrude oil Extreme salinity Haloarchaea Mercury resistance Mercury volatilization
The work has been supported by University of Kuwait, Research grant SL 08/07. Thanks are due to the SAF unit, Kuwait University for their help in GLC and ICP-MS analysis through GS 02/01 and GS 01/05.
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