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Iron-reducing bacteria could detoxify hexavalent chromium


Bacteria has important role in long-term


Hexavalent chromium is a major environmental contaminant at several Department of Energy (DOE) sites as well as other sites around the world.

The new study:
This study sheds light on the poorly understood process by which iron- reducing bacteria reduce ferric iron in clay minerals, resulting in ferrous iron that could then immobilize and detoxify chromium.

Results of the new study suggest that the iron- reducing activity of bacteria could be artificially stimulated to produce ferrous iron in clay minerals, which can then reduce hexavalent chromium to trivalent chromium. This promising strategy could potentially enable long-term remediation of heavy metal-contaminated sediments and groundwater aquifers worldwide.

Researchers at Environmental Molecular Sciences Laboratory (EMSL), a DOE national scientific user facility at Pacific Northwest National Laboratory, and Miami University added the iron-reducing bacterium Geobacter sulfurreducens to tubes filled with ferric iron-containing clay minerals such as smectites and chlorite. The researchers used ultra-sensitive microscopy and spectroscopy instruments located in the Quiet Wing, a specialized facility at EMSL, at national scientific user facility at Pacific Northwest National Laboratory. Specifically, they used scanning electron microscopy (SEM) with focused ion beam milling for thinning the samples and performing elemental mapping. They also used transmission electron microscopy (TEM) with electron energy loss spectroscopy for high-resolution imaging and for determining the valence state of chromium and iron before and after the reduction of hexavalent chromium by ferrous iron present in clay minerals.

The bacteria reduced ferric iron in the clay minerals at low rates when they were not stimulated with a compound known as anthraquinone-2,6-disulfonate (AQDS), which enhances their iron-reducing activity. Upon artificial stimulation with AQDS, the bacteria reduced ferric iron present in smectites and smectite-rich clays from DOE’s Hanford site, but not chlorite, at significantly higher rates. The resulting ferrous iron in the clay minerals reduced hexavalent chromium at higher rates with increasing temperatures, and at higher rates in smectites compared with chlorite. The observed hexavalent chromium reduction kinetics were well described by a second order rate equation with respect to concentrations of hexavalent chromium and ferrous iron.

SEM and TEM imaging revealed that trivalent chromium was intimately associated with the clay minerals, possibly in the form of sub-nanometer-sized chromium hydroxide embedded in the clay matrix. This structural feature is expected to minimize the secondary contamination risk of trivalent chromium being exposed to environmental oxidants and subsequently converting back to hexavalent chromium. Taken together, the findings suggest that in-situ stimulation of iron-reducing bacteria in iron-bearing clay minerals widely distributed in soils and sediments at contaminated sites may represent a promising strategy to stably immobilize chromium for long-term remediation efforts.

Source: (Adapted) from EMSL News

The cited study:

M.E. Bishop, P. Glasser, H. Dong, B. Arey, L. Kovarik, Reduction and immobilization of hexavalent chromium by microbially reduced Fe-bearing clay minerals, Geochim. Cosmochim. Acta, 133 (2014) 186-203. DOI: 10.1016/j.gca.2014.02.040

Related studies (newest first):

B. Dhal, H.N. Thatoi, N.N. Das, B.D. Pandey, Chemical and microbial remediation of hexavalent chromium from contaminated soil and mining/metallurgical solid waste: a review,  J. Hazard. Mater., 250–251 (2013) 272–291. DOI: 10.1016/j.jhazmat.2013.01.048

Mathur Nadarajan Kathiravan, Ramalingam Karthick, Karuppan Muthukumar, Ex situ bioremediation of Cr(VI) contaminated soil by Bacillus sp.: Batch and continuous studies, Chem. Engineer. J., 169 (2011) 107–115. doi: 10.1016/j.cej.2011.02.060

J. Jeyasingh, V. Somasundaram, Ligy Philip, S. Murty Bhallamudi, Bioremediation of Cr(VI) contaminated soil/sludge: Experimental studies and development of a management model, Chem. Engineer. J., 160/2 (2010) 556–564. DOI: 10.1016/j.cej.2010.03.067

Ahmed Zahoor, Abdul Rehman, Isolation of Cr(VI) reducing bacteria from industrial effluents and their potential use in bioremediation of chromium containing wastewater, J. Environ. Sci., 21/6 (2009) 814–820.  DOI: 10.1016/S1001-0742(08)62346-3

Guojun Cheng, Xiaohua Li, Bioreduction of chromium (VI) by Bacillus sp. isolated from soils of iron mineral area, Eur. J. Soil Biol., 45/5–6 (2009) 483–487. DOI: 10.1016/j.ejsobi.2009.06.009

Liyuan Chai, Shunhong Huang, Zhihui Yang, Bing Peng, Yan Huang,  Yuehui Chen, Cr(VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag, J. Hazard. Mater., 167/1–3 (2009) 516–522. DOI: 10.1016/j.jhazmat.2009.01.030

Chirayu Desai, Kunal Jain, Datta Madamwar, Hexavalent chromate reductase activity in cytosolic fractions of Pseudomonas sp. G1DM21 isolated from Cr(VI) contaminated industrial landfill, Process Biochem., 43/7 (2008)  713–721. DOI: 10.1016/j.procbio.2008.02.015

K.H. Cheung, Ji-Dong Gu, Mechanism of hexavalent chromium detoxification by microorganisms and bioremediation application potential: A review, Int. Biodeteriorat. Biodegrad., 59 (2007) 8–15. DOI: 10.1016/j.ibiod.2006.05.002

Zainul Akmar Zakaria, Zainoha Zakaria, Salmijah Surif, Wan Azlina Ahmad,
Hexavalent chromium reduction by Acinetobacter haemolyticus isolated from heavy-metal contaminated wastewater, J. Hazard. Mater., 146/1–2 (2007) 30–38.  DOI: 10.1016/j.jhazmat.2006.11.052

Zainul Akmar Zakaria, Zainoha Zakaria, Salmijah Surif, Wan Azlina Ahmad, Biological detoxification of Cr(VI) using wood-husk immobilized Acinetobacter haemolyticus, J. Hazard. Mater., 148 (2007) 164–171. doi: 10.1016/j.jhazmat.2007.02.029

Marta A. Polti, María J. Amoroso, Carlos M. Abate, Chromium(VI) resistance and removal by actinomycete strains isolated from sediments, Chemosphere, 67/4 (2007) 660–667. DOI: 10.1016/j.chemosphere.2006.11.008

Urvashi Thacker, Rasesh Parikh, Yogesh Shouche, Datta Madamwar, Reduction of chromate by cell-free extract of Brucella sp. isolated from Cr(VI) contaminated sites, Bioresource Technol., 98/8 (2007) 1541–1547.  DOI: 10.1016/j.biortech.2006.06.011  

Urvashi Thacker, Rasesh Parikh, Yogesh Shouche, Datta Madamwar, Hexavalent chromium reduction by Providencia sp., Process Biochem., 41/6 (2006) 1332–1337. DOI: 10.1016/j.procbio.2006.01.006

Yun-Guo Liu, Wei-Hua Xu, Guang-Ming Zeng, Xin Li, Hui Gao, Cr(VI) reduction by Bacillus sp. isolated from chromium landfill, Process Biochem., 41/9 (2006) 1981–1986. DOI: 10.1016/j.procbio.2006.04.020

J. Jeyasingh, Ligy Philip, Bioremediation of chromium contaminated soil: optimization of operating parameters under laboratory conditions, J. Hazard. Mater., 118/1–3 (2005) 113–120. DOI: 10.1016/j.jhazmat.2004.10.003.

K. Rama Krishna, Ligy Philip, Bioremediation of Cr(VI) in contaminated soils, J. Hazard. Mater., 121/1–3 (2005) 109–117. DOI: 10.1016/j.jhazmat.2005.01.018

Arundhati Pal, A.K. Paul, Aerobic chromate reduction by chromium-resistant bacteria isolated from serpentine soil, Microbiol. l Res., 159/4 (2004) 347–354. doi:  10.1016/j.micres.2004.08.001

R.S Laxman, S. More, Reduction of hexavalent chromium by Streptomyces griseus, Miner. Eng., 15/11 (2002) 831–837. DOI: 10.1016/S0892-6875(02)00128-0

T. Srinath, T. Verma, P.W. Ramteke, S.K. Garg, Chromium (VI) biosorption and bioaccumulation by chromate resistant bacteria, Chemosphere 48 (2002) 427–435. doi: 10.1016/S0045-6535(02)00089-9

V. Ernstsen, W.P. Gates, J.W. Stucki, Microbial reduction of structural iron in clays – a renewable source of reduction capacity, J. Environ. Qual., 27 (1998) 761–766. doi: 10.2134/jeq1998.00472425002700040006x

D.L. Sedlak, R.G. Chan, Reduction of hexavalent chromium by ferrous iron, Geochim. Cosmochim. Acta, 61 (1997) 2185–2192. doi: 10.1016/S0016-7037(97)00077-X

Yi-Tin Wang, Changsong Xiao, Factors affecting hexavalent chromium reduction in pure cultures of bacteria, Water Res., 29/11 (1995) 2467–2474. DOI: 10.1016/0043-1354(95)00093-Z

L.E. Eary, Dhanpat Rai, Kinetics of chromate reduction by ferrous ions derived from hematite and biotite at 25 degrees C., Am. J. Sci., 989 289 (1989) 180-213. doi:10.2475/ajs.289.2.180

L.E. Eary, D. Rai, Chromate removal from aqueous wastes by reduction with ferrous ion, Environ. Sci. Technol., 22 (1988) 972–977. DOI: 10.1021/es00173a018

 Related Information

CDC: Hexavalent chromium
About Environmental Issues: What is Hexavalent Chromium?
Strategic Environmental Research and Development Program (SERDP): Hexavalent Chromium
Worst Polluted: Tannerie Operations - Chromium Pollution
Worst Polluted: Top Six Toxic Threats: Chromium

 Related EVISA Resources

 Link Database: Toxicity of hexavalent chromium (chromate)
 Link Database: Industrial Use of chromate
 Link Database: Occupational exposure of hexavalent chromium
 Link Database: Legislation for hexavalent chromium at the workplace
 Link Database: Methods for chromium speciation analysis
Brief summary: The role of elemental speciation in legislation
Brief summary: Speciation and Toxicity
Brief summary: Standard methods for chromium speciation analysis

Related EVISA News

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February 15, 2010: Chromium speciation in solid matrices
February 3, 2009: New Reference Material for Hexavalent Chromium in Contaminated Soil
June 18, 2006: Bacteria supposed to remove poisonous arsenic from drinking water

last time modified: June 21, 2014


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