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Phenazines and Other Redox-Active Antibiotics Promote Microbial Mineral Reduction

Hernandez, Maria E. and Kappler, Andreas and Newman, Dianne K. (2004) Phenazines and Other Redox-Active Antibiotics Promote Microbial Mineral Reduction. Applied and Environmental Microbiology, 70 (2). pp. 921-928. ISSN 0099-2240. http://resolver.caltech.edu/CaltechAUTHORS:HERaem04

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Abstract

Natural products with important therapeutic properties are known to be produced by a variety of soil bacteria, yet the ecological function of these compounds is not well understood. Here we show that phenazines and other redox-active antibiotics can promote microbial mineral reduction. Pseudomonas chlororaphis PCL1391, a root isolate that produces phenazine-1-carboxamide (PCN), is able to reductively dissolve poorly crystalline iron and manganese oxides, whereas a strain carrying a mutation in one of the phenazine-biosynthetic genes (phzB) is not; the addition of purified PCN restores this ability to the mutant strain. The small amount of PCN produced relative to the large amount of ferric iron reduced in cultures of P. chlororaphis implies that PCN is recycled multiple times; moreover, poorly crystalline iron (hydr)oxide can be reduced abiotically by reduced PCN. This ability suggests that PCN functions as an electron shuttle rather than an iron chelator, a finding that is consistent with the observation that dissolved ferric iron is undetectable in culture fluids. Multiple phenazines and the glycopeptidic antibiotic bleomycin can also stimulate mineral reduction by the dissimilatory iron-reducing bacterium Shewanella oneidensis MR1. Because diverse bacterial strains that cannot grow on iron can reduce phenazines, and because thermodynamic calculations suggest that phenazines have lower redox potentials than those of poorly crystalline iron (hydr)oxides in a range of relevant environmental pH (5 to 9), we suggest that natural products like phenazines may promote microbial mineral reduction in the environment.


Item Type:Article
Additional Information:Copyright © 2004, American Society for Microbiology. Received 17 July 2003/ Accepted 3 November 2003 We thank J. Leadbetter and G. Bloemberg for stimulating discussions, S. Projan for the gift of purified bleomycin, G. Bloemberg for the gift of P. chlororaphis strains PCL1391 and PCL1119, and Kristina Straub for providing Geobacter strains Dfr1 and Dfr2. Support for this work was provided by grants to D.K.N. from the Office of Naval Research, the Luce Foundation, and the Packard Foundation.
Record Number:CaltechAUTHORS:HERaem04
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:HERaem04
Alternative URL:http://dx.doi.org/10.1128/AEM.70.2.921-928.2004
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2209
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:15 Mar 2006
Last Modified:26 Dec 2012 08:48

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