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Title: Iodate Reduction by Shewanella oneidensis Does Not Involve Nitrate Reductase

Abstract

Microbial iodate (IO 3 -) reduction is a major component of the iodine biogeochemical reaction network and is the basis of alternative strategies for remediation of iodine-contaminated environments. The molecular mechanism of microbial IO 3 - reduction, however, is not well understood. In microorganisms displaying IO 3 - and nitrate (NO 3 -) reduction activities, NO 3 - reductase is postulated to reduce IO 3 - as alternate electron acceptor. In the present study, whole genome analyses of 25 NO 3 --reducing Shewanella strains identified various combinations of genes encoding one assimilatory (cytoplasmic Nas) and three dissimilatory (membrane-associated Nar and periplasmic Napα and Napβ) NO 3 - reductases. S. oneidensis was the only Shewanella strain whose genome encoded a single NO 3 - reductase (Napβ). Terminal electron acceptor competition experiments in S. oneidensis batch cultures amended with both NO 3 - and IO 3 - demonstrated that neither NO 3 - nor IO 3 - reduction activities were competitively inhibited by the presence of the competing electron acceptor. The lack of involvement of S. oneidensis Napβ in IO 3 - reduction was confirmed via phenotypic analysis of an in-frame gene deletion mutant lacking napβΑ (encoding the NO 3 --reducing NapβAmore » catalytic subunit). S. oneidensis ΔnapβA was unable to reduce NO 3 -, yet reduced IO 3 - at rates higher than the wild-type strain. Thus, NapβA is required for dissimilatory NO 3 - reduction by S. oneidensis, while neither the assimilatory (Nas) nor dissimilatory (Napα, Napβ, and Nar) NO 3 - reductases are required for IO 3 - reduction. These findings oppose the traditional view that NO 3 - reductase reduces IO 3 - as alternate electron acceptor and indicate that S. oneidensis reduces IO 3 - via an as yet undiscovered enzymatic mechanism.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [1]
  1. School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  2. Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
  3. Environmental Stewardship Directorate, Savannah River National Laboratory, Aiken, SC, USA
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1455286
Report Number(s):
PNNL-SA-128629
Journal ID: ISSN 0149-0451; 830403000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Geomicrobiology Journal
Additional Journal Information:
Journal Volume: 35; Journal Issue: 7; Journal ID: ISSN 0149-0451
Country of Publication:
United States
Language:
English
Subject:
Hanford; iodine-129; bioremediation; attenuation

Citation Formats

Mok, Jung Kee, Toporek, Yael J., Shin, Hyun-Dong, Lee, Brady D., Lee, M. Hope, and DiChristina, Thomas J. Iodate Reduction by Shewanella oneidensis Does Not Involve Nitrate Reductase. United States: N. p., 2018. Web. doi:10.1080/01490451.2018.1430189.
Mok, Jung Kee, Toporek, Yael J., Shin, Hyun-Dong, Lee, Brady D., Lee, M. Hope, & DiChristina, Thomas J. Iodate Reduction by Shewanella oneidensis Does Not Involve Nitrate Reductase. United States. doi:10.1080/01490451.2018.1430189.
Mok, Jung Kee, Toporek, Yael J., Shin, Hyun-Dong, Lee, Brady D., Lee, M. Hope, and DiChristina, Thomas J. Thu . "Iodate Reduction by Shewanella oneidensis Does Not Involve Nitrate Reductase". United States. doi:10.1080/01490451.2018.1430189.
@article{osti_1455286,
title = {Iodate Reduction by Shewanella oneidensis Does Not Involve Nitrate Reductase},
author = {Mok, Jung Kee and Toporek, Yael J. and Shin, Hyun-Dong and Lee, Brady D. and Lee, M. Hope and DiChristina, Thomas J.},
abstractNote = {Microbial iodate (IO3-) reduction is a major component of the iodine biogeochemical reaction network and is the basis of alternative strategies for remediation of iodine-contaminated environments. The molecular mechanism of microbial IO3- reduction, however, is not well understood. In microorganisms displaying IO3- and nitrate (NO3-) reduction activities, NO3- reductase is postulated to reduce IO3- as alternate electron acceptor. In the present study, whole genome analyses of 25 NO3--reducing Shewanella strains identified various combinations of genes encoding one assimilatory (cytoplasmic Nas) and three dissimilatory (membrane-associated Nar and periplasmic Napα and Napβ) NO3- reductases. S. oneidensis was the only Shewanella strain whose genome encoded a single NO3- reductase (Napβ). Terminal electron acceptor competition experiments in S. oneidensis batch cultures amended with both NO3- and IO3- demonstrated that neither NO3- nor IO3- reduction activities were competitively inhibited by the presence of the competing electron acceptor. The lack of involvement of S. oneidensis Napβ in IO3- reduction was confirmed via phenotypic analysis of an in-frame gene deletion mutant lacking napβΑ (encoding the NO3--reducing NapβA catalytic subunit). S. oneidensis ΔnapβA was unable to reduce NO3-, yet reduced IO3- at rates higher than the wild-type strain. Thus, NapβA is required for dissimilatory NO3- reduction by S. oneidensis, while neither the assimilatory (Nas) nor dissimilatory (Napα, Napβ, and Nar) NO3- reductases are required for IO3- reduction. These findings oppose the traditional view that NO3- reductase reduces IO3- as alternate electron acceptor and indicate that S. oneidensis reduces IO3- via an as yet undiscovered enzymatic mechanism.},
doi = {10.1080/01490451.2018.1430189},
journal = {Geomicrobiology Journal},
issn = {0149-0451},
number = 7,
volume = 35,
place = {United States},
year = {2018},
month = {3}
}