Summary: APPLIED AND ENVIRONMENTAL MICROBIOLOGY, May 2002, p. 2445­2452 Vol. 68, No. 5
0099-2240/02/$04.00 0 DOI: 10.1128/AEM.68.5.2445­2452.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Diversity and Ubiquity of Bacteria Capable of Utilizing Humic
Substances as Electron Donors for Anaerobic Respiration
John D. Coates,* Kimberly A. Cole, Romy Chakraborty, Susan M. O'Connor, and
Laurie A. Achenbach
Department of Microbiology, Southern Illinois University, Carbondale, Illinois 62901
Received 6 November 2001/Accepted 19 February 2002
Previous studies have demonstrated that reduced humic substances (HS) can be reoxidized by anaerobic
bacteria such as Geobacter, Geothrix, and Wolinella species with a suitable electron acceptor; however, little is
known of the importance of this metabolism in the environment. Recently we investigated this metabolism in
a diversity of environments including marine and aquatic sediments, forest soils, and drainage ditch soils.
Most-probable-number enumeration studies were performed using 2,6-anthrahydroquinone disulfonate
(AHDS), an analog for reduced HS, as the electron donor with nitrate as the electron acceptor. Anaerobic
organisms capable of utilizing reduced HS as an electron donor were found in all environments tested and
ranged from a low of 2.31 101
in aquifer sediments to a high of 9.33 106
in lake sediments. As part of this
study we isolated six novel organisms capable of anaerobic AHDS oxidation. All of the isolates coupled the

Source: Achenbach, Laurie A. - Department of Microbiology, Southern Illinois University

Collections: Environmental Sciences and Ecology; Environmental Management and Restoration Technologies; Biology and Medicine