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Journal of Bacteriology, March 2007, p. 1774-1782, Vol. 189, No. 5
0021-9193/07/$08.00+0     doi:10.1128/JB.01395-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

The fox Operon from Rhodobacter Strain SW2 Promotes Phototrophic Fe(II) Oxidation in Rhodobacter capsulatus SB1003{triangledown}

Laura R. Croal,1,{dagger} Yongqin Jiao,2 and Dianne K. Newman1,2,3*

Division of Biology,1 Division of Geological and Planetary Sciences,2 Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 911253

Received 31 August 2006/ Accepted 12 December 2006

Anoxygenic photosynthesis based on Fe(II) is thought to be one of the most ancient forms of metabolism and is hypothesized to represent a transition step in the evolution of oxygenic photosynthesis. However, little is known about the molecular basis of this process because, until recently (Y. Jiao and D. K. Newman, J. Bacteriol. 189:1765-1773, 2007), most phototrophic Fe(II)-oxidizing bacteria have been genetically intractable. In this study, we circumvented this problem by taking a heterologous-complementation approach to identify a three-gene operon (the foxEYZ operon) from Rhodobacter sp. strain SW2 that confers enhanced light-dependent Fe(II) oxidation activity when expressed in its genetically tractable relative Rhodobacter capsulatus SB1003. The first gene in this operon, foxE, encodes a c-type cytochrome with no significant similarity to other known proteins. Expression of foxE alone confers significant light-dependent Fe(II) oxidation activity on SB1003, but maximal activity is achieved when foxE is expressed with the two downstream genes foxY and foxZ. In SW2, the foxE and foxY genes are cotranscribed in the presence of Fe(II) and/or hydrogen, with foxZ being transcribed only in the presence of Fe(II). Sequence analysis predicts that foxY encodes a protein containing the redox cofactor pyrroloquinoline quinone and that foxZ encodes a protein with a transport function. Future biochemical studies will permit the localization and function of the Fox proteins in SW2 to be determined.

* Corresponding author. Mailing address: 1200 E. California Blvd., M/C 100-23, Pasadena, CA 91125. Phone: (626) 395-6790. Fax: (626) 683-0621. E-mail: dkn{at}caltech.edu.

{triangledown} Published ahead of print on 22 December 2006.

{dagger} Present address: Massachusetts Institute of Technology, 15 Vassar St., 48-208, Cambridge. MA 02139.

Journal of Bacteriology, March 2007, p. 1774-1782, Vol. 189, No. 5
0021-9193/07/$08.00+0     doi:10.1128/JB.01395-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Poulain, A. J., Newman, D. K. (2009). Rhodobacter capsulatus Catalyzes Light-Dependent Fe(II) Oxidation under Anaerobic Conditions as a Potential Detoxification Mechanism. Appl. Environ. Microbiol. 75: 6639-6646 [Abstract] [Full Text]  
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