title: Phototrophic Fe(II) oxidation promotes organic carbon acquisition by Rhodobacter capsulatus SB1003.
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 it failed to grow lithoautotrophically on soluble Fe(II). When the strain was 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. The deletion of genes (RRC00247 and RRC00248) 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 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.
authors: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.
authors: Nicky C
authors: NC
authors: Caiazza
authors: Douglas P
authors: DP
authors: Lies
authors: Dianne K
authors: DK
authors: Newman
mesh_terms: D000693:Anaerobiosis; D002244:Carbon / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D052817:Phototrophic Processes; D016354:Rhodobacter capsulatus / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D005296:Ferrous Compounds; D009566:Nitrates; D002244:Carbon; D007501:Iron
references: Mol Microbiol. 1991 Oct;5(10):2519-27
references: 1791762
references: Gene. 1987;57(2-3):267-72
references: 3319781
references: Arch Biochem Biophys. 1975 Nov;171(1):14-26
references: 1103739
references: Photosynth Res. 2001;68(2):95-112
references: 16228333
references: J Biol Inorg Chem. 2006 Jul;11(5):633-41
references: 16791646
references: Arch Microbiol. 1999 Aug;172(2):116-24
references: 10415173
references: Geochim Cosmochim Acta. 2010 May 10;74(10):2826-2842
references: 21076519
references: Photochem Photobiol. 2006 Nov-Dec;82(6):1505-16
references: 16968114
references: J Bacteriol. 2004 Feb;186(3):595-600
references: 14729683
references: J Am Chem Soc. 2002 Jan 23;124(3):378-9
references: 11792199
references: Philos Trans R Soc Lond B Biol Sci. 2006 Oct 29;361(1474):1819-34; discussion 1835-6
references: 17008221
references: Arch Biochem Biophys. 1976 Sep;176(1):159-70
references: 9904
references: Nature. 2001 Sep 27;413(6854):409-13
references: 11574885
references: Appl Environ Microbiol. 1994 Dec;60(12):4517-26
references: 7811087
references: Biochem Biophys Res Commun. 1997 Sep 29;238(3):693-6
references: 9333139
references: Mol Gen Genet. 1988 Sep;214(1):97-107
references: 3067084
references: Biotechniques. 1992 Jul;13(1):18-20
references: 1503765
references: Photosynth Res. 2004;80(1-3):373-86
references: 16328834
references: Microbiology (Reading). 1998 Aug;144 ( Pt 8):2263-2269
references: 9720049
references: Microbiology (Reading). 1996 Apr;142(4):765-774
references: 33725793
references: Appl Environ Microbiol. 2005 Aug;71(8):4487-96
references: 16085840
references: Arch Microbiol. 2006 Jan;184(5):279-85
references: 16283252
references: Nat Rev Microbiol. 2006 Oct;4(10):752-64
references: 16980937
references: Science. 1970 Apr 24;168(3930):438-46
references: 4985766
references: Inorg Chem. 2006 Jul 24;45(15):6028-33
references: 16842010
references: J Bacteriol. 2007 Mar;189(5):1774-82
references: 17189371
references: Appl Environ Microbiol. 2006 Jul;72(7):5027-36
references: 16820502