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Mercuric Reductase for the Bioremediation of Mercury Contaminated Environments and Sources

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Hamza El Dorry
Professor of Molecular Biology
Rania Siam
Professor of Biology
Ahmed Sayed
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Ahmed Ellaithy
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Novel mercuric reductase and uses thereof

PCT Patent Application PCT/US14/63321
A Novel Mercuric Reductase from the Unique Deep Brine Environment of Atlantis II in the Red Sea
Journal of Biological Chemistry, VOL. 289, NO. 3, pp. 1675–1687, January 17, 2014


A novel multi-stress resistant Mercuric Reductase (AT-II merA) from the Red Sea Atlantis II Brine pool , used in the bioremediation of mercury contaminated environments and sources.


  • Engineering  bacteria for industrial bioremediation of mercurial contaminated environments.

  • Immobilizing (AT-II merA) into nanoparticles for removal of  mercury contamination from water sources.

  • Soil mercury removal by Phyto-remediation via host plant body.


The detoxification of mercury contaminated environments is of tremendous interest due to their hazardous effects on the ecosystem and ultimately human health. Mercury exposure is especially dangerous to pregnant women and young children, but all adults are at risk for serious medical problems. Most mercury pollution is produced by coal-fired power plants and other industrial processes. The most common way we are exposed to mercury is by eating contaminated fish.Methods useful for detoxification still remain highly challenging. Elemental mercury is not very toxic however,  Hg ²⁺ is toxic. The decontamination of Hg ²⁺  involves the reduction of Hg ²⁺ to  Hg⁰. The reaction is catalysed by MerA enzyme. Most enzymes do not show remarkable resistance to high temperature, salinity and high mercuric chloride concentrations.

Therefore , there remains a need for novel mercuric reductase polypeptides and for novel methods of removal of mercury from different environments.


AUC researches have discovered a novel mercuric reductase that is multi-stress resistant and can be used under very harsh conditions and still perform its job efficiently.  

The secret lies in the extremophilic bacteria that have learned to survive and adapt in the extreme Atlantis II brine pool environment, where there the water is characterized by acidic pH (5.3), high temperature (68 °C), high salinity (26%), low light levels, anoxia, and high concentrations of heavy metals.

A metagenomic dataset derived from that microbial community was established where a gene for a novel mercuric reductase - a key component of the bacterial detoxification system for elemental mercury- was identified.

Organisms extracted from the extreme Red Sea Atlantis II brine pool, were genetically modified using bioinformatic analysis and reverse engineering methods to express a mercuric reductase that is, in contrast to the soil enzyme, thermostable, halophilic (salt-tolerant) and of high detoxification activity. This novel biocatalyst has acquired its properties by having undergone multiple biochemical and biophysical adaptations to promote the survival of it’s microorganisms, that reside in the extremely demanding environment of the ATII-brine pool.


  • The Red Sea AT-II merA is 4 times resistant than any other reported mercuric reductase.

  • Exhibits high activity on mercury detoxification at 4M NaCl concentration.

  • Displays thermostability as high as 70°C

  • First report of mercuric reductase that is resistant to 3 harsh stressful conditions; high salinity, high temperature , high mercuric chloride conc.

  • The highly diversified ecosystem of the Red Sea, is utilized as a source for mining potential biocatalysts that can be used in potential  future applications.