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Applied and Environmental Microbiology, December 2005, p. 8419-8425, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.8419-8425.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Ecological Behavior of Lactobacillus reuteri 100-23 Is Affected by Mutation of the luxS Gene

Gerald W. Tannock,1* Salina Ghazally,1 Jens Walter,1 Diane Loach,1 Heather Brooks,1 Gregory Cook,1 Michael Surette,2 Cameron Simmers,3 Phil Bremer,3 Fabio Dal Bello,4 and Christian Hertel4

Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand,1 Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada,2 Department of Food Science, University of Otago, Dunedin, New Zealand,3 Institute of Food Technology, University of Hohenheim, Stuttgart, Germany4

Received 28 June 2005/ Accepted 6 September 2005

The luxS gene of Lactobacillus reuteri 100-23C was amplified by PCR, cloned, and then sequenced. To define a physiological and ecological role for the luxS gene in L. reuteri 100-23C, a luxS mutant was constructed by insertional mutagenesis. The luxS mutant did not produce autoinducers AI-2 or AI-3. Complementation of the luxS mutation by a plasmid construct containing luxS restored AI-2 and AI-3 synthesis. In vitro experiments revealed that neither the growth rate, nor the cell yield, nor cell survival in the stationary phase were compromised in the luxS mutant relative to the wild type and complemented mutant. The ATP content of exponentially growing cells of the luxS mutant was, however, 65% of that of wild-type cells. Biofilms formed by the luxS mutant on plastic surfaces in a bioreactor were thicker than those formed by the wild type. Biofilm thickness was not restored to wild-type values by the addition of purified AI-2 to the culture medium. In vivo experiments, conducted with ex-Lactobacillus-free mice, showed that biofilms formed by the mutant strain on the epithelial surface of the forestomach were approximately twice as thick as those formed by the wild type. The ecological performance of the luxS mutant, when in competition with L. reuteri strain 100-93 in the mouse cecum, was reduced compared to that of a xylA mutant of 100-23C. These results demonstrate that LuxS influences important ecological attributes of L. reuteri 100-23C, the consequences of which are niche specific.


* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin, New Zealand. Phone: 64-3-479-7713. Fax: 64-3-479-8540. E-mail: gerald.tannock{at}stonebow.otago.ac.nz.


Applied and Environmental Microbiology, December 2005, p. 8419-8425, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.8419-8425.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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