Insights into the interactions of cyanobacteria with uranium
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REVIEW
Insights into the interactions of cyanobacteria with uranium Celin Acharya • Shree Kumar Apte
Received: 5 April 2013 / Accepted: 23 September 2013 / Published online: 8 October 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract Due to various activities associated with nuclear industry, uranium is migrated to aquatic environments like groundwater, ponds or oceans. Uranium forms stable carbonate complexes in the oxic waters of pH 7–10 which results in a high degree of uranium mobility. Microorganisms employ various mechanisms which significantly influence the mobility and the speciation of uranium in aquatic environments. Uranyl bioremediation studies, this far, have generally focussed on low pH conditions and related to adsorption of positively charged UO22? onto negatively charged microbial surfaces. Sequestration of anionic ura4nium species, i.e. [UO2(CO3)22 ] and [UO2(CO3)3 ] onto microbial surfaces has received only scant attention. Marine cyanobacteria are effective metal adsorbents and represent an important sink for metals in aquatic environment. This article addresses the cyanobacterial interactions with toxic metals in general while stressing on uranium. It focusses on the possible mechanisms employed by cyanobacteria to sequester uranium from aqueous solutions above circumneutral pH where negatively charged uranyl carbonate complexes dominate aqueous uranium speciation. The mechanisms demonstrated by cyanobacteria are important components of biogeochemical cycle of uranium and are useful for the development of appropriate strategies, either to recover or remediate uranium from the aquatic environments.
C. Acharya S. K. Apte (&) Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India e-mail: [email protected]; [email protected] C. Acharya e-mail: [email protected]
Keywords Cyanobacteria Uranium Interaction mechanisms Bioremediation Biorecovery
Introduction Increasing contamination of the environment by uranium on account of its mining and disposal of tailings, nuclear power/weapons production, nuclear testing or nuclear accidents is a worldwide problem. Microbial interactions with metals form an important part of the natural biogeochemical processes and have important consequences for human society. It is therefore vital to advance our understanding of the metal–microbe interactions to develop suitable bioremediation strategies for metal-contaminated sites. The versatility of microbial systems to remove heavy metals and radionuclides from their immediate environment is well recognized. Microbes influence the environmental fate of metals by employing diverse physicochemical and biological mechanisms, effecting changes in the mobility and speciation of metals. As a consequence, microbial bioremediation of radionuclide pollutants is being actively explored currently. Cyanobacteria represent a morphologically diverse group of oxygenic, gram-negative photosynthetic prokaryotes, which are widely distributed in freshwater, marine and terrestrial
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