Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS
Volume 4, Issue 11, Pages 500-504Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.estlett.7b00471
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Funding
- Natural Science Foundation of China [51538012, 51478446]
- Recruitment Program of Global Experts
- Fundamental Research Funds for the Central Universities
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Cr isotope fractionation during microbial reduction processes is commonly recognized as a promising tool in biogeochemistry and bioremediation. However, the mechanism of Cr isotope fractionation during microbial reduction is poorly understood. In this work, the relationship between the bacterial respiratory pathway and Cr isotope fractionation was investigated in Shewanella oneidensis MR-1. For comparison with the wild type, a mutant strain (Delta omcA/Delta mtrC) with a deficiency in extracellular Cr(VI) reduction was constructed by deleting the omcA and mtrC genes, which encode the terminal reductase during extracellular reduction. The magnitudes of Cr isotope fractionation (epsilon) for Cr(VI) reduction by the wild type and Delta omcA/Delta mtrC were -2.42 +/- 0.68 parts per thousand and -2.70 +/- 0.22 parts per thousand, respectively. Surprisingly, the e values were not significantly different between the two strains. This suggests that isotope fractionation is independent of the metal respiratory pathway during Cr(VI) reduction by S. oneidensis MR-1. Moreover, a three-step Cr isotope fractionation model that includes uptake, reduction, and efflux was proposed to exist during intracellular Cr(VI) reduction by S. oneidensis MR-1. The developed model provides a better understanding of Cr isotope fractionation during microbial reduction.
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