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Journal of Bacteriology, June 2004, p. 3408-3414, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3408-3414.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

A Cambialistic Superoxide Dismutase in the Thermophilic Photosynthetic Bacterium Chloroflexus aurantiacus

Vanessa L. Lancaster,1 Russell LoBrutto,2 Fabiyola M. Selvaraj,1,{dagger} and Robert E. Blankenship1*

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604,1 School of Life Sciences, Arizona State University, Tempe, Arizona 85287-45012

Received 28 October 2003/ Accepted 17 February 2004

Superoxide dismutase from the thermophilic anoxygenic photosynthetic bacterium Chloroflexus aurantiacus was cloned, purified, and characterized. This protein is in the manganese- and iron-containing family of superoxide dismutases and is able to use both manganese and iron catalytically. This appears to be the only soluble superoxide dismutase in C. aurantiacus. Iron and manganese cofactors were identified by using electron paramagnetic resonance spectroscopy and were quantified by atomic absorption spectroscopy. By metal enrichment of growth media and by performing metal fidelity studies, the enzyme was found to be most efficient with manganese incorporated, yet up to 30% of the activity was retained with iron. Assimilation of iron or manganese ions into superoxide dismutase was also found to be affected by the growth conditions. This enzyme was also found to be remarkably thermostable and was resistant to H2O2 at concentrations up to 80 mM. Reactive oxygen defense mechanisms have not been previously characterized in the organisms belonging to the phylum Chloroflexi. These systems are of interest in C. aurantiacus since this bacterium lives in a hyperoxic environment and is subject to high UV radiation fluxes.

* Corresponding author. Mailing address: Department of Chemistry and Biochemistry, Arizona State University, P.O. Box 871604, Tempe, AZ 85287-1604. Phone: (480) 965-4430. Fax: (480) 965-2747. E-mail: Blankenship{at}asu.edu.

{dagger} Present address: Ribomed, Phoenix, AZ 85040.

Journal of Bacteriology, June 2004, p. 3408-3414, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3408-3414.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.





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