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Journal of Bacteriology, August 2008, p. 5607-5615, Vol. 190, No. 16
0021-9193/08/$08.00+0     doi:10.1128/JB.00319-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Genetic Analysis of Spirochete Flagellin Proteins and Their Involvement in Motility, Filament Assembly, and Flagellar Morphology{triangledown}

Chunhao Li,1 Charles W. Wolgemuth,2 Michael Marko,3 David G. Morgan,4 and Nyles W. Charon5*

Department of Oral Biology, State University of New York at Buffalo, Buffalo, New York 14214,1 Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut 06030-3505,2 Resource for Visualization of Biological Complexity, Wadsworth Center, Albany, New York 12201-0509,3 Department of Chemistry, Indiana University, 800 E. Kirkland Ave, Bloomington, Indiana 47405,4 Department of Microbiology, Immunology and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506-91775

Received 4 March 2008/ Accepted 3 June 2008

The filaments of spirochete periplasmic flagella (PFs) have a unique structure and protein composition. In most spirochetes, the PFs consist of a core of at least three related proteins (FlaB1, FlaB2, and FlaB3) and a sheath of FlaA protein. The functions of these filament proteins remain unknown. In this study, we used a multidisciplinary approach to examine the role of these proteins in determining the composition, shape, and stiffness of the PFs and how these proteins impact motility by using the spirochete Brachyspira (formerly Treponema, Serpulina) hyodysenteriae as a genetic model. A series of double mutants lacking combinations of these PF proteins was constructed and analyzed. The results show the following. First, the diameters of PFs are primarily determined by the sheath protein FlaA, and that FlaA can form a sheath in the absence of an intact PF core. Although the sheath is important to the PF structure and motility, it is not essential. Second, the three core proteins play unequal roles in determining PF structure and swimming speed. The functions of the core proteins FlaB1 and FlaB2 overlap such that either one of these proteins is essential for the spirochete to maintain the intact PF structure and for cell motility. Finally, linear elasticity theory indicates that flagellar stiffness directly affects the spirochete's swimming speed.

* Corresponding author. Mailing address: Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506-9177. Phone: (304) 293-4170. Fax: (304) 293-7823. E-mail: ncharon{at}hsc.wvu.edu

{triangledown} Published ahead of print on 13 June 2008.

Journal of Bacteriology, August 2008, p. 5607-5615, Vol. 190, No. 16
0021-9193/08/$08.00+0     doi:10.1128/JB.00319-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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