Team:SDU-Denmark/project-t

From 2010.igem.org

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Bacteria have evolved many modes of propulsion for the microscale environments they inhabit. At these scales materials behave very different than at macroscale, and of particular interest to us is the way liquids seem more viscous [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 1]]. One of the many ways bacteria move around in liquids, is by means of flagella. A single flagellum is a thin filament around 100-150 Å thick, that extends many cell lengths out from the cell [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 2]]. It consists mainly of flagellin subunits that assemble into a helical structure forming a long hollow cylindrical filament [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 3]]. In ''E. coli'' the mean number of flagella per cell is 4 [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], but there is a wide variance between strains, and even between individual cells of each strain. The environment around the cell also has a large influence on how many flagellae are present, or if they are present at all [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]]. Flagella rotate to generate force that allows bacterial cells to swim through fluids in characteristic patterns, more on which later, in search of better conditions for proliferation or survival [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 5]]. Normally flagellated strains of ''E. coli'' can achieve speeds up to 20µm/sec [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], and considering a cell length of only 1-2µm, this is an impressive feat indeed.<br><br>
Bacteria have evolved many modes of propulsion for the microscale environments they inhabit. At these scales materials behave very different than at macroscale, and of particular interest to us is the way liquids seem more viscous [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 1]]. One of the many ways bacteria move around in liquids, is by means of flagella. A single flagellum is a thin filament around 100-150 Å thick, that extends many cell lengths out from the cell [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 2]]. It consists mainly of flagellin subunits that assemble into a helical structure forming a long hollow cylindrical filament [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 3]]. In ''E. coli'' the mean number of flagella per cell is 4 [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], but there is a wide variance between strains, and even between individual cells of each strain. The environment around the cell also has a large influence on how many flagellae are present, or if they are present at all [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]]. Flagella rotate to generate force that allows bacterial cells to swim through fluids in characteristic patterns, more on which later, in search of better conditions for proliferation or survival [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 5]]. Normally flagellated strains of ''E. coli'' can achieve speeds up to 20µm/sec [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], and considering a cell length of only 1-2µm, this is an impressive feat indeed.<br><br>
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A flagellum  is anchored to the cell body by a large, wheel-like protein complex spanning both inner and outer membranes [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]]. Through this complex subunits are secreted to the tip of the flagellar tube[[https://2010.igem.org/Team:SDU-Denmark/project-t#References 3]], thus elongating the filament (This mechanism is slightly different in archaea, where the filament is assembled from the base of the flagellum). The membrane anchor also functions as a rotary engine, driven by the proton motive force [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]]. In ''E. coli'' the flagellar motor rotates at up to 300hz and can turn either clockwise or counter-clockwise [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], both resulting in a distinct movement pattern for the cell.<br><br>
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A flagellum  is anchored to the cell body by a large, wheel-like protein complex spanning both inner and outer membranes [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]]. Through this complex subunits are secreted to the tip of the flagellar tube [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 3]], thus elongating the filament (This mechanism is slightly different in archaea, where the filament is assembled from the base of the flagellum). The membrane anchor also functions as a rotary engine, driven by the proton motive force [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]]. In ''E. coli'' the flagellar motor rotates at up to 300hz and can turn either clockwise or counter-clockwise [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], both resulting in a distinct movement pattern for the cell.<br><br>
Spinning in the counter-clockwise direction, the flagella will twist into a bundle in the shape of a corkscrew, and create a linear driving force [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], propelling the cell in a straight line through the liquid. This form of movement is termed run. Spun in the clockwise direction one might then expect the cell to reverse, but this is not the case. Instead the flagellar bundle will unwind, thereby creating chaotic movement [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]] . This movement reorients the cell randomly and is termed tumbling. A cell will typically run for some time, then change it’s orientation by tumbling, and then run again [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 5]]. The direction of flagella rotation is controlled by the binding of a cytosolic protein CheY, more on which later [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]].<br><br>
Spinning in the counter-clockwise direction, the flagella will twist into a bundle in the shape of a corkscrew, and create a linear driving force [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]], propelling the cell in a straight line through the liquid. This form of movement is termed run. Spun in the clockwise direction one might then expect the cell to reverse, but this is not the case. Instead the flagellar bundle will unwind, thereby creating chaotic movement [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]] . This movement reorients the cell randomly and is termed tumbling. A cell will typically run for some time, then change it’s orientation by tumbling, and then run again [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 5]]. The direction of flagella rotation is controlled by the binding of a cytosolic protein CheY, more on which later [[https://2010.igem.org/Team:SDU-Denmark/project-t#References 4]].<br><br>

Revision as of 18:31, 27 October 2010