Growth of Flagellar Filaments of Escherichia coli is Independent of Filament Length
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CitationTurner, Linda, Alan S. Stern, and Howard C. Berg. 2012. Growth of flagellar filaments of Escherichia coli is independent of filament length. Journal of Bacteriology 194(10): 2437-2442.
AbstractBacterial ﬂagellar ﬁlaments grow at their distal ends, from ﬂagellin that travels through a central channel \(\sim 2 nm\) in diameter. The ﬂagellin is extruded from the cytoplasm by a pump powered by a proton motive force (PMF). We measured ﬁlament growth in cells near the mid-exponential-phase with ﬂagellin bearing a speciﬁc cysteine-for-serine substitution, allowing ﬁlaments to be labeled with sulfhydryl-speciﬁc ﬂuorescent dyes. We labeled ﬁlaments ﬁrst with a green maleimide dye and then, following an additional period of growth, with a red maleimide dye. The contour lengths of the green and red segments were measured. The average lengths of red segments \((2.3 \mu m)\) were the same regardless of the lengths of the green segments from which they grew (ranging from less than 1 to more than \(9 \mu m\) in length). Thus, ﬂagellar ﬁlaments do not grow at a rate that decreases exponentially with length, as formerly supposed. If ﬂagellar ﬁlaments were broken by viscous shear, the broken ﬁlaments continued to grow. Identical results were obtained whether ﬂagellin was expressed from ﬂiC on the chromosome under the control of its native promoter or on a plasmid under the control of the arabinose promoter.
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