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Journal of Bacteriology, December 2003, p. 7140-7144, Vol. 185, No. 24
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.24.7140-7144.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Transcriptional Regulation and Posttranslational Activity of the Betaine Transporter BetL in Listeria monocytogenes Are Controlled by Environmental Salinity

Roy D. Sleator,1 Janet M. Wood,2 and Colin Hill1*

Department of Microbiology and Alimentary Pharmabiotic Centre, University College, Cork, Ireland,1 Department of Microbiology, University of Guelph, Guelph, Ontario, Canada N1G 2W12

Received 2 July 2003/ Accepted 15 September 2003

While the genetic elements contributing to the salinity tolerance of Listeria monocytogenes have been well characterized, the regulatory signals and responses (genetic and/or biochemical) that govern these mechanisms have yet to be elucidated. Encoded by betL, the first genetic element to be linked to listerial osmotolerance, the secondary betaine uptake system BetL is a member of the betaine-carnitine-choline transporter family. Preceded by consensus {sigma}A- and {sigma}B-dependent promoter sites, betL is constitutively expressed and transcriptionally up-regulated in response to salt stress. The nisin-controlled expression system was used to achieve salinity-independent, controlled betL expression in Listeria. In the absence of NaCl-activated transcriptional control, BetL activity was found to be a function of environmental salinity, showing optimal activity in buffer supplemented with 1 to 2% NaCl (osmolality, 417 to 719 mosmol/kg). In addition, BetL was activated rapidly (half-life, 2 min) in response to an osmotic upshift imposed by adding 2% NaCl to 50 mM potassium phosphate buffer.

* Corresponding author. Mailing address: Department of Microbiology, University College, Cork, Ireland. Phone: 353-21-4901374. Fax: 353-21-4903101. E-mail: c.hill{at}ucc.ie.

Journal of Bacteriology, December 2003, p. 7140-7144, Vol. 185, No. 24
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.24.7140-7144.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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  • Sheehan, V. M., Sleator, R. D., Fitzgerald, G. F., Hill, C. (2006). Heterologous Expression of BetL, a Betaine Uptake System, Enhances the Stress Tolerance of Lactobacillus salivarius UCC118.. Appl. Environ. Microbiol. 72: 2170-2177 [Abstract] [Full Text]  


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