Abstract:
Many bacteria swim by rotating helical flagellar filaments. Waterbury et al. discovered an exception, strains of the cyanobacterium Synechococcus that swim without flagella or visible changes in shape. Other species of cyanobacteria glide on surfaces. The hypothesis that Synechococcus might swim using traveling surface waves prompted this investigation.
Results
Using quick-freeze electron microscopy, we have identified a crystalline surface layer that encloses the outer membrane of the motile strain Synechococcus sp. WH8113, the components of which are arranged in a rhomboid lattice. Spicules emerge in profusion from the layer and extend up to 150 nm into the surrounding fluid. These spicules also send extensions inwards to the inner cell membrane where motility is powered by an ion-motive force.
Conclusion
The envelope structure of Synechococcus sp. WH8113 provides new constraints on its motile mechanism. The spicules are well positioned to transduce energy at the cell membrane into mechanical work at the cell surface. One model is that an unidentified motor embedded in the cell membrane utilizes the spicules as oars to generate a traveling wave external to the surface layer in the manner of ciliated eukaryotes.
Description:
© 2001 Samuel et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. The definitive version was published in BMC Microbiology 1 (2001): 4, doi:10.1186/1471-2180-1-4.
Except where otherwise noted, this item's license is described as http://creativecommons.org/licenses/by/2.0