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Applied and Environmental Microbiology, December 2008, p. 7675-7683, Vol. 74, No. 24
0099-2240/08/$08.00+0     doi:10.1128/AEM.01229-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

A Putative ABC Transporter Is Involved in Negative Regulation of Biofilm Formation by Listeria monocytogenes

Xinna Zhu,^1,2 Fei Long,¹ Yonghui Chen,¹ Susanne Knøchel,³ Qunxin She,^2* and Xianming Shi^1*

Department of Food Science and Technology and Bor Luh Food Safety Center, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China,¹ Danish Archaea Centre, Functional Genomics Section, Department of Biology, University of Copenhagen, Biocenter Copenhagen, Ole Maaloes Vej 5, DK-2200 Copenhagen N, Denmark,² Food Microbiology, Department of Food Science, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark³

Received 3 June 2008/ Accepted 30 September 2008

Listeria monocytogenes may persist for long periods in food processing environments. In some instances, this may be due to aggregation or biofilm formation. To investigate the mechanism controlling biofilm formation in the food-borne pathogen L. monocytogenes, we characterized LM-49, a mutant with enhanced ability of biofilm formation generated via transposon Tn917 mutagenesis of L. monocytogenes 4b G. In this mutant, a Tn917 insertion has disrupted the coding region of the gene encoding a putative ATP-binding cassette (ABC) transporter permease identical to Lmof2365_1771 (a putative ABC transporter permease) presented in the sequenced strain L. monocytogenes strain 4b F2365. This disrupted gene, denoted lm.G_1771, encoded a protein with 10 transmembrane helixes. The revertant, LM-49RE, was obtained by replacing lm.G_1771::Tn917 with lm.G_1771 via homologous recombination. We found that LM-49RE formed the same amount of biofilm biomass as the wild-type strain. Furthermore, transcription of the downstream lm.G_1770 gene was not influenced by the upstream Tn917 insertion, and the presence of Tn917 has no effect on biofilm formation. These results suggest that lm.G_1771 was solely responsible for the negative regulation of biofilm formation by L. monocytogenes 4b G. The immediate gene upstream of lm.G_1771 encoded an ATP-binding protein. Bioinformatics analysis suggested that these two genes were organized into an operon and that their proteins formed an export ABC transporter. Here, we report the characterization of the mutant and identification of a novel ABC transporter that functions in negative regulation of biofilm formation in L. monocytogenes.

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* Corresponding author. Mailing address for Xianming Shi: Department of Food Science and Technology, Shanghai Jiao Tong University, 800 Dong Chuan Rd., Shanghai 200240, People's Republic of China. Phone and fax: 86 21 3420 6616. E-mail: xmshi{at}sjtu.edu.cn. Mailing address for Qunxin She: Danish Archaea Centre, Functional Genomics Section, Department of Biology, University of Copenhagen, Biocenter Copenhagen, Ole Maaloes Vej 5, DK-2200 Copenhagen N, Denmark. Phone: 45 35 32 20 13. Fax: 45 35 32 21 28. E-mail: qunxin{at}bio.ku.dk

Published ahead of print on 3 October 2008.

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Applied and Environmental Microbiology, December 2008, p. 7675-7683, Vol. 74, No. 24
0099-2240/08/$08.00+0     doi:10.1128/AEM.01229-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.