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Applied and Environmental Microbiology, February 2008, p. 774-782, Vol. 74, No. 3
0099-2240/08/$08.00+0     doi:10.1128/AEM.01960-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Enzymic Approach to Eurythermalism of Alvinella pompejana and Its Episymbionts{triangledown} ,{dagger}

Charles K. Lee,1 S. Craig Cary,1,2 Alison E. Murray,3 and Roy M. Daniel1*

Department of Biological Sciences, University of Waikato, Hamilton, New Zealand,1 College of Marine and Earth Studies, University of Delaware, Lewes, Delaware,2 Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, Nevada3

Received 27 August 2007/ Accepted 29 November 2007

The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

* Corresponding author. Mailing address: Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand. Phone: 64-7-838-4213. Fax: 64-7-838-4324. E-mail: r.daniel{at}waikato.ac.nz

{triangledown} Published ahead of print on 14 December 2007.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, February 2008, p. 774-782, Vol. 74, No. 3
0099-2240/08/$08.00+0     doi:10.1128/AEM.01960-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Grzymski, J. J., Murray, A. E., Campbell, B. J., Kaplarevic, M., Gao, G. R., Lee, C., Daniel, R., Ghadiri, A., Feldman, R. A., Cary, S. C. (2008). Metagenome analysis of an extreme microbial symbiosis reveals eurythermal adaptation and metabolic flexibility. Proc. Natl. Acad. Sci. USA 105: 17516-17521 [Abstract] [Full Text]  


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