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Journal of Bacteriology, June 2008, p. 4291-4300, Vol. 190, No. 12
0021-9193/08/$08.00+0     doi:10.1128/JB.00023-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Inactivation of lsr2 Results in a Hypermotile Phenotype in Mycobacterium smegmatis ^,

Kriti Arora,¹ Danelle C. Whiteford,¹ Dalia Lau-Bonilla,¹ Christine M. Davitt,² and John L. Dahl^1*

School of Molecular Biosciences, Washington State University, Pullman, Washington 99164,¹ Franceschi Microscopy and Imaging Center, College of Sciences, Washington State University, Pullman, Washington 99164²

Received 4 January 2008/ Accepted 2 April 2008

Mycobacterial species are characterized by the presence of lipid-rich, hydrophobic cell envelopes. These cell envelopes contribute to properties such as roughness of colonies, aggregation of cells in liquid culture without detergent, and biofilm formation. We describe here a mutant strain of Mycobacterium smegmatis, called DL1215, which demonstrates marked deviations from the above-mentioned phenotypes. DL1215 arose spontaneously from a strain deficient for the stringent response (M. smegmatis rel_Msm strain) and is not a reversion to a wild-type phenotype. The nature of the spontaneous mutation was a single base-pair deletion in the lsr2 gene, leading to the formation of a truncated protein product. The DL1215 strain was complicated by having both inactivated rel_Msm and lsr2 genes, and so a single lsr2 mutant was created to analyze the gene's function. The lsr2 gene was inactivated in the wild-type M. smegmatis mc²155 strain by allelic replacement to create strain DL2008. Strain DL2008 shows characteristics unique from those of both the wild-type and rel_Msm strains, some of which include a greatly enhanced ability to slide over agar surfaces (referred to here as "hypermotility"), greater resistance to phage infection and to the antibiotic kanamycin, and an inability to form biofilms. Complementation of the DL2008 mutant with a plasmid containing lsr2 (pLSR2) reverts the strain to the mc²155 phenotype. Although these phenotypic differences allude to changes in cell surface lipids, no difference is observed in glycopeptidolipids, polar lipids, apolar lipids, or mycolic acids of the cell wall.

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* Corresponding author. Mailing address: Washington State University, School of Molecular Biosciences, Abelson Hall, Room 301, Pullman, WA 99164. Phone: (509) 335-7719. Fax: (509) 335-1907. E-mail: johndahl{at}wsu.edu

Published ahead of print on 11 April 2008.

Supplemental material for this article may be found at http://jb.asm.org/.

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Journal of Bacteriology, June 2008, p. 4291-4300, Vol. 190, No. 12
0021-9193/08/$08.00+0     doi:10.1128/JB.00023-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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