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Phototrophic Fe(II) Oxidation Promotes Organic Carbon Acquisition by Rhodobacter capsulatus SB1003

Caiazza, Nicky C. and Lies, Douglas P. and Newman, Dianne K. (2007) Phototrophic Fe(II) Oxidation Promotes Organic Carbon Acquisition by Rhodobacter capsulatus SB1003. Applied and Environmental Microbiology, 73 (19). pp. 6150-6158. ISSN 0099-2240. http://resolver.caltech.edu/CaltechAUTHORS:CAIaem07

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Abstract

Anoxygenic phototrophic Fe(II) oxidation is usually considered to be a lithoautotrophic metabolism that contributes to primary production in Fe-based ecosystems. In this study, we employed Rhodobacter capsulatus SB1003 as a model organism to test the hypothesis that phototrophic Fe(II) oxidation can be coupled to organic carbon acquisition. R. capsulatus SB1003 oxidized Fe(II) under anoxic conditions in a light-dependent manner, but failed to grow lithoautotrophically on soluble Fe(II). When provided with Fe(II)-citrate, however, growth was observed that was dependent upon microbially catalyzed Fe(II) oxidation, resulting in the formation of Fe(III)-citrate. Subsequent photochemical breakdown of Fe(III)-citrate yielded acetoacetic acid, that supported growth in the light but not the dark. Deletion of genes (RR00247-RR00248) that encode homologs of atoA and atoD, required for acetoacetic acid utilization, severely impaired the ability of R. capsulatus SB1003 to grow on Fe(II)-citrate. The growth yield achieved by R. capsulatus SB1003 in the presence of citrate cannot be explained by lithoautotrophic growth on Fe(II) enabled by indirect effects of the ligand (such as altering the thermodynamics of Fe(II) oxidation or preventing cell encrustation). Together, these results demonstrate that R. capsulatus SB1003 grows photoheterotrophically on Fe(II)-citrate. Nitrilotriacetic acid (NTA) also supported light-dependent growth on Fe(II), suggesting that Fe(II) oxidation may be a general mechanism whereby some Fe(II)-oxidizing bacteria mine otherwise inaccessible organic carbon sources.


Item Type:Article
ORCID:
AuthorORCID
Newman, Dianne K.0000-0003-1647-1918
Additional Information:Copyright © 2007, American Society for Microbiology and/or the Listed Authors/Institutions. AEM Accepts, published online ahead of print on 10 August 2007. Final published version, Copyright © 2007, American Society for Microbiology. Received 5 December 2006/ Accepted 1 August 2007. We thank Yun Wang for expertise and technical assistance with HPLC. We also thank Yongqin Jiao and anonymous reviewers for their constructive comments on the manuscript. This work was supported by grants from the Howard Hughes Medical Institute and Packard Foundation to D.K.N.
Record Number:CaltechAUTHORS:CAIaem07
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:CAIaem07
Alternative URL:http://dx.doi.org/10.1128/AEM.02830-06
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8601
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:22 Aug 2007
Last Modified:24 Oct 2017 15:06

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