Transformation of straight flagella and recovery of motility in a mutant Escherichia coli

The flagellar filament enables bacteria to swim by functioning as a helical propeller. The filament is a supercoiled assembly of a single protein, flagellin, and is formed by 11 protofilaments arranged in a circle. Bacterial swimming and tumbling correlate with changes of the various helical structures, called polymorphic transformation, that are determined by the ratios of two distinct forms of protofilaments, the L and R types. The polymorphic transformation is caused by transition of the protofilament between L and R types. Elucidation of this transition mechanism has been addressed by comparing the atomic structures of L-and R-type straight filaments or using massive molecular dynamic simulation. Here, we found amino acid residues required for the transition of the protofilament using fliC-intragenic suppressor analysis. We isolated a number of revertants producing supercoiled filaments from mutants with straight filaments and identified the second-site mutations in all of the revertants. The results suggest that Asp107, Gly426, and Ser448 and Ser106, Ala416, Ala427, and Arg431 are the key residues involved in inducing supercoiled filaments from the R-and the L-type straight filaments, respectively. Considering the structures of the R-and L-type protofilaments and the relationship between the rotation of the flagellar motor and the polymorphic transformation, we propose that Gly426, Ala427, and Arg431 contribute to the first stage of the transition and that Ser106, Asp107, and Ala416 play a role in propagating the transitions along the flagellar filament.

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“…1). These properties are consistent with those of the straightfilament mutants described previously (36).…”

Section: Resultssupporting

confidence: 91%

Key Amino Acid Residues Involved in the Transitions of L- to R-Type Protofilaments of the Salmonella Flagellar Filament

et al. 2013

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“…Direct evidence was obtained that the S-shaped end is left-handed and gyrates CCW. In cells swimming parallel to the cover glass, the sense of winding of a helix-right-handed or left-handed-can be surmised from the direction of slant of portions of the cell in photographs focused above or below the helix axis (22,23). As shown in Fig.…”

Section: Resultsmentioning

confidence: 98%

“…Cells were illuminated stroboscopically for viewing and multipleexposure photography. Analyses of cell shapes and motions were facilitated by focusing above and below the axis of the cells (22,23) and by slowing the motions of the cells by suspending them in Ficoll (24).…”

mentioning

confidence: 99%

Multiple-exposure photographic analysis of a motile spirochete.

Goldstein

Charon

1990

Proc. Natl. Acad. Sci. U.S.A.

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The Leptospiraceae are thin spirochetes with a unique mode of motility. These spiral-shaped bacteria have internal periplasmic flagella that propel the cells in lowviscosity and gel-like high-viscosity media. A model of Leptospiraceae motility has been previously proposed that states that the subterminally attached periplasmic flagella rotate between the outer sheath and the helical protoplasmic cylinder. The shape of the cell ends and the direction of gyration of these ends are determined by the direction of rotation of the internal periplasmic flagella. Rotation of the periplasmic flagella in one direction causes that end to be spiral-shaped, and rotation in the other direction causes that end to be hook-shaped. One prediction of the model is that these right-handed spirochetes roll clockwise when swimming away from an observer. For maximum swimming efficiency, the model predicts that the sense of the spiral-shaped end is left-handed and gyrates counterclockwise. The present study presents direct evidence that the cell rolls clockwise (protoplasmic cylinder helix diameter = 0.24 ,jm; pitch = 0.69 jam), the ends gyrate counterclockwise, and the spiral-shaped end is left-handed (helix diameter = 0.6 jam; pitch = 2.7 ,jm)-as predicted by the model. The hook-shaped end appears approximately planar. The approach used was to illuminate stroboscopically cells slowed by Ficoll and analyze the resultant multiple-exposure photographs focused above and below the axis of the cell. The methodology used should be helpful in analyzing the motility of the larger and more complex spirochetes.

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“…Since the flagellar filaments of E. coli and S. typhimurium are relatively stiff, a helical shape is necessary to escape the constraints of the scallop theorem, since a straight rod rotating about its axis generates no propulsion. Indeed, mutant E. coli with straight flagella do not swim [125]. If the rate of rotation of a straight but flexible rod is high enough for the hydrodynamic torque to twist the rod through about one turn, then the rod will buckle into a gently helical shape that can generate thrust [126][127][128].…”

Section: Boundary Actuationmentioning

confidence: 99%

The hydrodynamics of swimming microorganisms

2009

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Cell motility in viscous fluids is ubiquitous and affects many biological processes, including reproduction, infection and the marine life ecosystem. Here we review the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming, tens of micrometers and below. At this scale, inertia is unimportant and the Reynolds number is small. Our emphasis is on the simple physical picture and fundamental flow physics phenomena in this regime. We first give a brief overview of the mechanisms for swimming motility, and of the basic properties of flows at low Reynolds number, paying special attention to aspects most relevant for swimming such as resistance matrices for solid bodies, flow singularities and kinematic requirements for net translation. Then we review classical theoretical work on cell motility, in particular early calculations of swimming kinematics with prescribed stroke and the application of resistive force theory and slender-body theory to flagellar locomotion. After examining the physical means by which flagella are actuated, we outline areas of active research, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers and the optimization of locomotion strategies.

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Transformation of straight flagella and recovery of motility in a mutant Escherichia coli

Cited by 13 publications

References 19 publications

Key Amino Acid Residues Involved in the Transitions of L- to R-Type Protofilaments of the Salmonella Flagellar Filament

Key Amino Acid Residues Involved in the Transitions of L- to R-Type Protofilaments of the Salmonella Flagellar Filament

Multiple-exposure photographic analysis of a motile spirochete.

The hydrodynamics of swimming microorganisms

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