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Journal of Bacteriology, October 2004, p. 6885-6890, Vol. 186, No. 20
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.20.6885-6890.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

A pH-Sensitive Function and Phenotype: Evidence that EutH Facilitates Diffusion of Uncharged Ethanolamine in Salmonella enterica

Joseph T. Penrod, Christopher C. Mace,{dagger} and John R. Roth*

Section of Microbiology, University of California, Davis, California

Received 5 June 2004/ Accepted 28 July 2004

The eutH gene is part of an operon that allows Salmonella enterica to use ethanolamine as a sole source of nitrogen, carbon, and energy. Although the sequence of EutH suggests a role in transport, eutH mutants use ethanolamine normally under standard conditions (pH 7.0). These mutants fail to use ethanolamine at a low pH. Evidence is presented that protonated ethanolamine (Eth0) does not enter cells, while uncharged ethanolamine (Eth0) diffuses freely across the membrane. The external concentration of Eth0 varies with the pH (pK = 9.5). At pH 7.0, the standard ethanolamine concentration (41 mM) provides enough Eth0 for an influx rate that can support growth with or without EutH. When a lowered pH and/or ethanolamine concentration reduced the Eth0 concentration below 25 µM, EutH was needed to facilitate diffusion. EutH+ cells grew normally at Eth0 concentrations above 3 µM, close to the Km (9 µM) of the first degradative enzyme, ethanolamine ammonia lyase. It is suggested that EutH facilitates diffusion of Eth0. As predicted for a transporter, EutH contributed to the toxicity of ethanolamine seen under some conditions; furthermore, fusion of EutH to fluorescent Yfp protein provided evidence that EutH is a membrane protein.

* Corresponding author. Mailing address: One Shields Ave., Davis, CA 95616. Phone: (530) 752-6679. Fax: (530) 752-7663. E-mail: jrroth{at}ucdavis.edu.

{dagger} Present address: Genentech, South San Francisco, CA 94080-4990.

Journal of Bacteriology, October 2004, p. 6885-6890, Vol. 186, No. 20
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.20.6885-6890.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Del Papa, M. F., Perego, M. (2008). Ethanolamine Activates a Sensor Histidine Kinase Regulating Its Utilization in Enterococcus faecalis. J. Bacteriol. 190: 7147-7156 [Abstract] [Full Text]  
  • Penrod, J. T., Roth, J. R. (2006). Conserving a Volatile Metabolite: a Role for Carboxysome-Like Organelles in Salmonella enterica.. J. Bacteriol. 188: 2865-2874 [Abstract] [Full Text]  
  • Brinsmade, S. R., Paldon, T., Escalante-Semerena, J. C. (2005). Minimal Functions and Physiological Conditions Required for Growth of Salmonella enterica on Ethanolamine in the Absence of the Metabolosome. J. Bacteriol. 187: 8039-8046 [Abstract] [Full Text]  


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