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Title: Dual Role of Humic Substances As Electron Donor and Shuttle for Dissimilatory Iron Reduction

Dissimilatory iron-reducing bacteria (DIRB) are known to use humic substances (HS) as electron shuttles for dissimilatory iron reduction (DIR) by transferring electrons to HS-quinone moieties, which in turn rapidly reduce Fe(III) oxides. However, the potential for HS to serve as a source of organic carbon (OC) that can donate electrons for DIR is unknown. We studied whether humic acids (HA) and humins (HM) recovered from peat soil by sodium pyrophosphate extraction could serve as both electron shuttles and electron donors for DIR by freshwater sediment microorganisms. Both HA and HM served as electron shuttles in cultures amended with glucose. However, only HA served as an electron donor for DIR. Metagenomes from HA-containing cultures had an overrepresentation of genes involved in polysaccharide and to a lesser extent aromatic compound degradation, suggesting complex OC metabolism. Genomic searches for the porin-cytochrome complex involved in DIR resulted in matches to Ignavibacterium/Melioribacter, DIRB capable of polymeric OC metabolism. These results indicate that such taxa may have played a role in both DIR and decomposition of complex OC. Our results suggest that decomposition of HS coupled to DIR and other anaerobic pathways could play an important role in soil and sediment OC metabolism.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ; ORCiD logo [1] ; ORCiD logo [4]
  1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering, Environmental Chemistry and Technology Program
  2. Univ. of Wisconsin, Madison, WI (United States). Dept. of Geoscience, Dept. of Bacteriology
  3. Univ. of Nevada, Reno, NV (United States). Dept. of Civil and Environmental Engineering
  4. Univ. of Wisconsin, Madison, WI (United States). Dept. of Geoscience
Publication Date:
Grant/Contract Number:
SC0016217
Type:
Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 52; Journal Issue: 10; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of Wisconsin, Madison, WI (United States); Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Orgs:
SBR Scientific Focus Area at the Pacific Northwest National Laboratory (PNNL)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1469803
Alternate Identifier(s):
OSTI ID: 1480447

Stern, Noah, Mejia, Jacqueline, He, Shaomei, Yang, Yu, Ginder-Vogel, Matthew, and Roden, Eric E. Dual Role of Humic Substances As Electron Donor and Shuttle for Dissimilatory Iron Reduction. United States: N. p., Web. doi:10.1021/acs.est.7b06574.
Stern, Noah, Mejia, Jacqueline, He, Shaomei, Yang, Yu, Ginder-Vogel, Matthew, & Roden, Eric E. Dual Role of Humic Substances As Electron Donor and Shuttle for Dissimilatory Iron Reduction. United States. doi:10.1021/acs.est.7b06574.
Stern, Noah, Mejia, Jacqueline, He, Shaomei, Yang, Yu, Ginder-Vogel, Matthew, and Roden, Eric E. 2018. "Dual Role of Humic Substances As Electron Donor and Shuttle for Dissimilatory Iron Reduction". United States. doi:10.1021/acs.est.7b06574. https://www.osti.gov/servlets/purl/1469803.
@article{osti_1469803,
title = {Dual Role of Humic Substances As Electron Donor and Shuttle for Dissimilatory Iron Reduction},
author = {Stern, Noah and Mejia, Jacqueline and He, Shaomei and Yang, Yu and Ginder-Vogel, Matthew and Roden, Eric E.},
abstractNote = {Dissimilatory iron-reducing bacteria (DIRB) are known to use humic substances (HS) as electron shuttles for dissimilatory iron reduction (DIR) by transferring electrons to HS-quinone moieties, which in turn rapidly reduce Fe(III) oxides. However, the potential for HS to serve as a source of organic carbon (OC) that can donate electrons for DIR is unknown. We studied whether humic acids (HA) and humins (HM) recovered from peat soil by sodium pyrophosphate extraction could serve as both electron shuttles and electron donors for DIR by freshwater sediment microorganisms. Both HA and HM served as electron shuttles in cultures amended with glucose. However, only HA served as an electron donor for DIR. Metagenomes from HA-containing cultures had an overrepresentation of genes involved in polysaccharide and to a lesser extent aromatic compound degradation, suggesting complex OC metabolism. Genomic searches for the porin-cytochrome complex involved in DIR resulted in matches to Ignavibacterium/Melioribacter, DIRB capable of polymeric OC metabolism. These results indicate that such taxa may have played a role in both DIR and decomposition of complex OC. Our results suggest that decomposition of HS coupled to DIR and other anaerobic pathways could play an important role in soil and sediment OC metabolism.},
doi = {10.1021/acs.est.7b06574},
journal = {Environmental Science and Technology},
number = 10,
volume = 52,
place = {United States},
year = {2018},
month = {4}
}