Spatial arrangement of several flagellins within bacterial flagella improves motility in different environments

Abstract

Bacterial flagella are helical proteinaceous fibers, composed of the protein flagellin, that confer motility to many bacterial species. The genomes of about half of all flagellated species include more than one flagellin gene, for reasons mostly unknown. Here we show that two flagellins (FlaA and FlaB) are spatially arranged in the polar flagellum of Shewanella putrefaciens, with FlaA being more abundant close to the motor and FlaB in the remainder of the flagellar filament. Observations of swimming trajectories and numerical simulations demonstrate that this segmentation improves motility in a range of environmental conditions, compared to mutants with single-flagellin filaments. In particular, it facilitates screw-like motility, which enhances cellular spreading through obstructed environments. Similar mechanisms may apply to other bacterial species and may explain the maintenance of multiple flagellins to form the flagellar filament.

Haloarchaea swim slowly for optimal chemotactic efficiency in low nutrient environments

“…Digital holographic microscopy. Our cell tracking experiments were performed using digital holographic microscopy, as described elsewhere 12,[46][47][48] . The samples were imaged on a Nikon Ti inverted microscope.…”

“…A separate software routine was used to identify which coordinates in subsequent frames correspond to the same cell, based on their proximity. These coordinates were arranged into tracks and smoothed using piecewise cubic splines in order to remove noise in the cell coordinates and improve estimates of cell velocity as described in previous work 12 . Examining the mean-squared displacement of the cells' smoothed trajectories allowed us to discriminate between swimming and diffusing cells, and to discard the latter.…”

Systematic functional analysis of Leishmania protein kinases identifies regulators of differentiation or survival

“…The corrected movies were then thresholded to highlight cells moving by either swimming or Brownian motion. The cell coordinates in each frame were extracted, and these coordinates were assembled into cell tracks using customwritten software routines 71 . To smooth short-time fluctuations associated with camera noise, the cell tracks were fitted using piecewise cubic splines.…”

High speed, three-dimensional imaging reveals chemotactic behavior specific to human-infectiveLeishmaniaparasites

“…The holographic microscopy setup was similar to that used previously [32,33], with a few modifications. The samples were imaged on a Nikon Eclipse E600 upright microscope.…”

“…A separate software routine was used to compare the putative cell coordinates extracted in each frame and associate those most likely to constitute cell tracks. The tracks were smoothed using piecewise cubic splines in order to remove noise in the cell coordinates and provide better estimates of cell velocity as described in previous work [33]. Examining the mean-squared displacement of the cells' smoothed trajectories allowed us to discriminate between swimming and diffusing cells, and to discard the latter.…”