The clockwise-rotating rhizobial flagellar motor
The bacterial flagellum is a complex self-assembling macromolecular machine that requires more than 50 proteins for formation, regulation, and function. As an adaptation to the viscous soil environment, Sinorhizobium meliloti and other plant-interacting rhizobial soil bacteria developed a unique flagellar motor. One major difference between the S. meliloti and the enterobacterial system is the presence of four flagellin subunits (Fla A-D), which form complex, more rigid filaments, which makes it more efficient in the viscous milieu of the soil. We have also shown that directional changes of a swimming cell are caused by the uni-directional clockwise (cw) rotation of several flagella at different speeds. Uni-directional rotation of the flagellar motor, paired with speed variation, required the evolution of additional proteins. This research aims towards an understanding of the role of unique motor proteins in rhizobial motility.
M.A.B. Kreutzberger, Sobe R., Sauder A.B., Chatterjee S., Pena A., Wang F., Giron J.A., Kiessling V., Costa T.R.D., Conticello V.P., Frankel G., Kendall M.M., Scharf B.E.* Egelman E.H.* (2022) Dimerization and tetramerization of flagellin outer domains modulate polymorphism and motility in pathogenic E. coli and soil bacteria. Nature Communications, 7;13(1):1422. *Co-corresponding authors.
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