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Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism

Poulain, Alexandre J. and Newman, Dianne K. (2009) Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism. Applied and Environmental Microbiology, 75 (21). pp. 6639-6646. ISSN 0099-2240. PMCID PMC2772431. http://resolver.caltech.edu/CaltechAUTHORS:20130430-132656400

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Abstract

Diverse bacteria are known to oxidize millimolar concentrations of ferrous iron [Fe(II)] under anaerobic conditions, both phototrophically and chemotrophically. Yet whether they can do this under conditions that are relevant to natural systems is understood less well. In this study, we tested how light, Fe(II) speciation, pH, and salinity affected the rate of Fe(II) oxidation by Rhodobacter capsulatus SB1003. Although R. capsulatus cannot grow photoautotrophically on Fe(II), it oxidizes Fe(II) at rates comparable to those of bacteria that do grow photoautotrophically on Fe(II) as soon as it is exposed to light, provided it has a functional photosystem. Chelation of Fe(II) by diverse organic ligands promotes Fe(II) oxidation, and as the pH increases, so does the oxidation rate, except in the presence of nitrilotriacetate; nonchelated forms of Fe(II) are also more rapidly oxidized at higher pH. Salt concentrations typical of marine environments inhibit Fe(II) oxidation. When growing photoheterotrophically on humic substances, R. capsulatus is highly sensitive to low concentrations of Fe(II); it is inhibited in the presence of concentrations as low as 5 μM. The product of Fe(II) oxidation, ferric iron, does not hamper growth under these conditions. When other parameters, such as pH or the presence of chelators, are adjusted to promote Fe(II) oxidation, the growth inhibition effect of Fe(II) is alleviated. Together, these results suggest that Fe(II) is toxic to R. capsulatus growing under strictly anaerobic conditions and that Fe(II) oxidation alleviates this toxicity.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1128/AEM.00054-09DOIArticle
http://aem.asm.org/content/75/21/6639PublisherArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2772431/PubMed CentralArticle
ORCID:
AuthorORCID
Newman, Dianne K.0000-0003-1647-1918
Additional Information:© 2009 American Society for Microbiology. Received 9 January 2009; Accepted 22 August 2009. Published ahead of print on 28 August 2009. We thank Andrew Lang from Memorial University of Newfoundland and Labrador and Tom Beatty from the University of British Columbia for providing the puhA mutant. We thank Bronwyn Keatley, Sebastian Kopf, and other members of the Newman lab for stimulating discussions. This work was supported by grants to D.K.N. from the National Science Foundation (grant MCB-0616323) and the Howard Hughes Medical Institute and by a postdoctoral fellowship from the Natural Science and Engineering Council of Canada to A.J.P.
Funders:
Funding AgencyGrant Number
NSFMCB-0616323
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
PubMed Central ID:PMC2772431
Record Number:CaltechAUTHORS:20130430-132656400
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130430-132656400
Official Citation:Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism Alexandre J. Poulain and Dianne K. Newman Appl. Environ. Microbiol. November 1, 2009 75:21 6639-6646; published ahead of print 28 August 2009, doi:10.1128/AEM.00054-09
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38188
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 May 2013 19:16
Last Modified:24 Oct 2017 15:54

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