Journal of Bacteriology, April 2002, p . 1817, Vol . 184, No . 7

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 .

FOOTNOTES

The views expressed in this Commentary do not necessarily reflect the views of the journal or of ASM .

REFERENCES

1. 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
2. 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.
3. Miyata, M., W . S . Ryu, and H . C . Berg. 2001 . Force and velocity of Mycoplasma mobile gliding . J . Bacteriol . 184:1827-1831.
4. Scheffers, D., and A . J . Driessen. 2001 . The polymerization mechanism of the bacterial cell division protein FtsZ . FEBS Lett . 506:6-10.
5. 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.

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