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Journal of Bacteriology, January 2006, p. 525-531, Vol. 188, No. 2
0021-9193/06/$08.00+0     doi:10.1128/JB.188.2.525-531.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Characterization of Dissimilatory Fe(III) versus NO3– Reduction in the Hyperthermophilic Archaeon Pyrobaculum aerophilum

Lawrence F. Feinberg and James F. Holden*

Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003

Received 23 August 2005/ Accepted 18 October 2005

The hyperthermophilic archaeon Pyrobaculum aerophilum used 20 mM Fe(III) citrate, 100 mM poorly crystalline Fe(III) oxide, and 10 mM KNO3 as terminal electron acceptors. The two forms of iron were reduced at different rates but with equal growth yields. The insoluble iron was reduced when segregated spatially by dialysis tubing, indicating that direct contact with the iron was not necessary for growth. When partitioned, there was no detectable Fe(III) or Fe(II) outside of the tubing after growth, suggesting that an electron shuttle, not a chelator, may be used as an extracellular mediator of iron reduction. The addition of 25 and 50% (vol vol–1) cell-free spent insoluble iron media to fresh media led to growth without a lag phase. Liquid chromatography analysis of spent media showed that cultures grown in iron, especially insoluble iron, produced soluble extracellular compounds that were absent or less abundant in spent nitrate medium. NADH-dependent ferric reductase activity increased approximately 100-fold, while nitrate reductase activity decreased 10-fold in whole-cell extracts from iron-grown cells relative to those from nitrate-grown cells, suggesting that dissimilatory iron reduction was regulated. A novel 2,6-anthrahydroquinone disulfonate oxidase activity was more than 580-fold higher in iron-grown cells than in nitrate-grown cells. The activity was primarily (>95%) associated with the membrane cellular fraction, but its physiological function is unknown. Nitrate-grown cultures produced two membrane-bound, c-type cytochromes that are predicted to be monoheme and part of nitrite reductase and a bc1 complex using genome analyses. Only one cytochrome was present in cells grown on Fe(III) citrate whose relative abundance was unchanged.

* Corresponding author. Mailing address: N207 Morrill Science Center IV North, Department of Microbiology, University of Massachusetts, Amherst, MA 01003. Phone: (413) 577-1742. Fax: (413) 545-1578. E-mail: jholden{at}microbio.umass.edu.

Journal of Bacteriology, January 2006, p. 525-531, Vol. 188, No. 2
0021-9193/06/$08.00+0     doi:10.1128/JB.188.2.525-531.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Cozen, A. E., Weirauch, M. T., Pollard, K. S., Bernick, D. L., Stuart, J. M., Lowe, T. M. (2009). Transcriptional Map of Respiratory Versatility in the Hyperthermophilic Crenarchaeon Pyrobaculum aerophilum. J. Bacteriol. 191: 782-794 [Abstract] [Full Text]  
  • Feinberg, L. F., Srikanth, R., Vachet, R. W., Holden, J. F. (2008). Constraints on Anaerobic Respiration in the Hyperthermophilic Archaea Pyrobaculum islandicum and Pyrobaculum aerophilum. Appl. Environ. Microbiol. 74: 396-402 [Abstract] [Full Text]  
  • Hu, Y., Holden, J. F. (2006). Citric Acid Cycle in the Hyperthermophilic Archaeon Pyrobaculum islandicum Grown Autotrophically, Heterotrophically, and Mixotrophically with Acetate.. J. Bacteriol. 188: 4350-4355 [Abstract] [Full Text]  


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