Document Detail

Electron shuttling via humic acids in microbial iron(III) reduction in a freshwater sediment.
MedLine Citation:
PMID:  19712349     Owner:  NLM     Status:  MEDLINE    
The biological and chemical potential for electron shuttling via humic acids was evaluated by analyzing the depth distribution of humic-acid-reducing and iron-reducing bacteria in a freshwater sediment, and correlating it to the redox characteristics of humic acids and iron. Physicochemical analysis of profundal sediments of Lake Constance revealed a distinct stratification, with oxygen respiration, microbial iron and sulfate reduction, and methanogenesis allocatable to defined layers. Among the acid-extractable iron in the surface layer, ferric iron (Fe(III)) was dominant, whereas ferrous iron (Fe(II)) prevailed below 2 cm depth. Humic acids showed a higher electron-accepting (oxidizing) capacity in the surface layer and a higher reducing capacity in deeper layers. The more reduced redox state of humic acids in deeper layers was probably due to reduction by humic-acid-reducing microorganisms. Most-probable-number analysis revealed that the sediments contained populations of humic-acid-reducing bacteria that (i) were substantially larger than those of the iron-reducing bacteria in the respective sediment layers and (ii) were in the same range as those of the fermenting bacteria. Our results suggest that microbial reduction of humic acids and subsequent chemical reduction of poorly soluble iron(III) minerals by the reduced humic acids represents an important path of electron flow in anoxic natural environments such as freshwater sediments.
Andreas Kappler; Marcus Benz; Bernhard Schink; Andreas Brune
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  FEMS microbiology ecology     Volume:  47     ISSN:  1574-6941     ISO Abbreviation:  FEMS Microbiol. Ecol.     Publication Date:  2004 Jan 
Date Detail:
Created Date:  2009-08-28     Completed Date:  2009-09-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8901229     Medline TA:  FEMS Microbiol Ecol     Country:  England    
Other Details:
Languages:  eng     Pagination:  85-92     Citation Subset:  IM    
Fachbereich Biologie, Lehrstuhl für Mikrobielle Okologie und Limnologie, Universität Konstanz, Germany.
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MeSH Terms
Bacteria / metabolism*
Colony Count, Microbial
Electron Transport*
Ferric Compounds / metabolism*
Fresh Water / chemistry,  microbiology*
Geologic Sediments / chemistry,  microbiology*
Humic Substances*
Iron / chemistry,  metabolism*
Methane / metabolism
Oxygen Consumption
Sulfates / metabolism
Reg. No./Substance:
0/Ferric Compounds; 0/Humic Substances; 0/Sulfates; 74-82-8/Methane; 7439-89-6/Iron

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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