Journal of Bacteriology, April 2002, p. 1817, Vol. 184, No. 7
0021-9193/02/$04.00+0 DOI: 10.1128/JB.184.7.1817.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
| GUEST COMMENTARY |
Forcing Mycoplasma mobile into Line
Shahid Khan*
Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York
Mycoplasmas are parasitic bacteria lacking a cell wall but possessing an internal cytoskeletal structure. In this issue, Miyata and coworkers report measurements of the force-velocity relation of Mycoplasma mobile gliding on a glass substrate at different temperatures (3). Protein A-conjugated polystyrene beads coated with antibodies raised against M. mobile proteins were attached to the tail ends of gliding bacteria. The hydrodynamic drag of beads on cells gliding upstream against fluid flow was used to define the force-velocity relation. In addition, the beads were used as handles to stall bacteria by an optical laser trap, with displacement of the bead in the trap defining the stall force. The hydrodynamic drag to movement against fluid flow exerted by the beads could be precisely estimated. Miyata et al. found linear force velocity relations, a temperature-independent stall force of 26 pN, and speeds up to 3.3 µm/s at 27.5°C at zero force.
This study adds a new dimension to the existing literature on gliding motility. The Berg laboratory has pioneered the development of laser trap technology for analysis of molecular motor mechanics (1). Now, innovative application of this methodology to Mycoplasma gliding motility defines the force generation capability of this motility form with a precision not possible with simpler assays. The data set important constraints that should both spur attempts to discover the thus-far mysterious molecular machinery and provide criteria that candidate molecules, once identified, will ultimately need to satisfy. Interestingly, the bacteria orient in response to flow and move upstream in a second or so. When flow is turned off, they disorient on a similar time scale. Video documentation is available from the sixth BLAST meeting review (2) video link (http://stock.cabm.rutgers.edu/mem/stock/blast_19.html#A). Could stress-induced assembly and disassembly of cytoskeletal structure play a role here, as in actin-based amoeboid motility, coupled to force generation by a molecular motor? Members of the actin or microtubule-based cytoskeletal motor protein families have not been found in bacteria so far. However, particularly in pathogenic bacteria with long-standing associations with eukaryotic hosts, molecules are being uncovered that either interact with known cytoskeletal elements or behave as cytoskeletal analogs (4, 5). Miyata et al. note that the filamentous structure seen in Mycoplasma by electron microscopy is associated with the adhesion protein and, thus, may provide a possible scaffold for the substantial forces documented by their work. If so, the mechanisms that underlie prokaryotic gliding motility and eukaryotic amoeboid motility could turn out to be more similar than previously imagined.
* Mailing address: Department of Biochemistry & Molecular Biology, 4295 Weiskotten Hall Addition, SUNY Upstate Medical University, Syracuse, NY 13210. Phone: (315) 464-8729. Fax: (315) 464-8750. E-mail: KhanSM{at}mail.upstate.edu.
FOOTNOTES
The views expressed in this Commentary do not necessarily reflect the views of the journal or of ASM.
REFERENCES
- Berry, R. M., and H. C. Berg. 1997. Absence of a barrier to backwards rotation of the bacterial flagellar motor demonstrated with optical tweezers. Proc. Natl. Aca. Sci. USA 94:14433-14437
[Abstract/Free Full Text] - Bourret, R. B., N. W. Charon, A. M. Stock, and A. H. West. 2002. Bright Lights, Abundant Operons—Fluorescence and Genomic Technologies Advance Studies of Bacterial Locomotion and Signal Transduction: Review of the BLAST Meeting, Cuernavaca, Mexico, 14 to 19 January 2001. J. Bacteriol. 184:1-17.
- Miyata, M., W. S. Ryu, and H. C. Berg. 2001. Force and velocity of Mycoplasma mobile gliding. J. Bacteriol. 184:1827-1831.
- Scheffers, D., and A. J. Driessen. 2001. The polymerization mechanism of the bacterial cell division protein FtsZ. FEBS Lett. 506:6-10.[CrossRef][Medline]
- Zhou, D., M. S. Mooseker, and J. E. Galan. 1999. An invasion-associated Salmonella protein modulates the actin-bundling activity of plastin. Proc. Natl. Acad. Sci. USA 96:10176-10181.
[Abstract/Free Full Text]
Journal of Bacteriology, April 2002, p. 1817, Vol. 184, No. 7
0021-9193/02/$04.00+0 DOI: 10.1128/JB.184.7.1817.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
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