Figure 1.
Schematic representations of the digital in-line holographic microscopy setup.
(A) The holographic device used in this study consists of the laser source, adjustment mirrors, apertures, a beam expander, the objective, a pinhole and a CMOS camera. B) schematic geometry of the beam path behind the 500 nm pinhole with geometric dimensions relevant for the reconstruction process.
Figure 2.
Percentage of covered area on swimming agar for eight different strains of P. aeruginosa.
The strains were inoculated in the middle of semisolid swimming agar plates and incubated for 48°C in order to investigate the ability for flagellar-mediated swimming. Values represent the mean of three agar plates, error bars are the standard deviations.
Figure 3.
Representation of P.aeruginosa trajectories showing different swimming patterns.
(A) 3D representation of trajectories of P. aeruginosa. The optical path and thus the real space orientation of the 3D cubus is illustrated. (B) xy-projection of trajectories of P. aeruginosa as viewed along the optical path. In some trajectories loops can be observed which are marked with black arrows. (C) Schematical representation of 5 different swimming patterns observed for P. aeruginosa after tracking of 35 individual bacteria. The different patterns are termed (1) meander, (2) oscillation, (3) helix, (4) pseudohelix and (5) twisting. (D) Probability to observe the classified swimming patterns meander, oscillation, helix, pseudohelix and twisting within a trajectory. Values represent the average over 35 trajectories with the corresponding standard error.
Figure 4.
3D trajectories of P. aeruginosa with transitions between different motion patterns.
(A) Trajectory with a duration of 110 s with switching between the meander and the oscillation pattern. a) and b) illustrate extracted segments of the meander and the oscillation pattern in two different viewing directions indicated by the black arrows. (B) Trajectory with a duration of 130 s with switching between the three different patterns pseudohelix, helix and twisting. The individual segments of each pattern are illustrated in a), b) and c).
Table 1.
Ratio between straight line velocity (SLV) and curvilinear velocity (CLV) referred to as linearity.
Figure 5.
Segments of helical swimming patterns.
(A) and (B) 3D representation and view along the helical axis of a right-handed helical segment with 4 loops. (C) and (D) 3D representation and view along the helical axis of a left-handed helix with 3 loops. The start and the end points of the segments are labeled by triangles and rectangles respectively. The blue dots represent the unsmoothed data points, the red line shows the resulting trajectory after smoothing the data with local polynomial regression fitting.
Figure 6.
Transition of loop handedness.
(A) Percentage of right-handed and left-handed loops determined by analyzing 55 loops in the helical and pseudohelical swimming pattern segments. (B) Extracted segment showing a transition between left-handed (LH) and right-handed (RH) loops. The triangle and the rectangle label the start and the end point of the segment, respectively.
Figure 7.
Segments of trajectories showing oscillatory swimming patterns.
(A) and (B) Two different viewing direction of a hair-pin-like pattern with short run phases and sharp turning angles α1, α2 and α3. (C) and (D) Two different viewing directions of oscillatory segment with less sharp reversal points P1, P2 and P3.
Figure 8.
Turning angles of the hair-pin-like pattern.
(A) Illustration for the calculation of the turning angles α. The angle is calculated from three consecutive displacement vectors and describes the deviation from a linear motion. (B) Calculated turning angles α (blue) and z-coordinate of the positions (green) of the hair-pin-like pattern in Figures 7A–B.