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Emergence of complex behavior in pili-based motility in early stages of P. aeruginosa surface adaptation

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ABSTRACT

Pseudomonas aeruginosa move across surfaces by using multiple Type IV Pili (TFP), motorized appendages capable of force generation via linear extension/retraction cycles, to generate surface motions collectively known as twitching motility. Pseudomonas cells arrive at a surface with low levels of piliation and TFP activity, which both progressively increase as the cells sense the presence of a surface. At present, it is not clear how twitching motility emerges from these initial minimal conditions. Here, we build a simple model for TFP-driven surface motility without complications from viscous and solid friction on surfaces. We discover the unanticipated structural requirement that TFP motors need to have a minimal amount of effective angular rigidity in order for cells to perform the various classes of experimentally-observed motions. Moreover, a surprisingly small number of TFP are needed to recapitulate movement signatures associated with twitching: Two TFP can already produce movements reminiscent of recently observed slingshot type motion. Interestingly, jerky slingshot motions characteristic of twitching motility comprise the transition region between different types of observed crawling behavior in the dynamical phase diagram, such as self-trapped localized motion, 2-D diffusive exploration, and super-diffusive persistent motion.

No MeSH data available.


Slow and fast modes.(a) Part of a trajectory from computer simulations. Red dots indicate pilus-release events, blue arrows point on fast jumps, with above-threshold velocity of 0.07 μm/s. Jumps always occur after a release, however not all the release event result in a jump. (b) Time evolution of the x-coordinate and its time derivative. The parameters used here are KRel = 130 s−1, KAd = 5 s−1, ka = 10−14 and ν = π/8.
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f4: Slow and fast modes.(a) Part of a trajectory from computer simulations. Red dots indicate pilus-release events, blue arrows point on fast jumps, with above-threshold velocity of 0.07 μm/s. Jumps always occur after a release, however not all the release event result in a jump. (b) Time evolution of the x-coordinate and its time derivative. The parameters used here are KRel = 130 s−1, KAd = 5 s−1, ka = 10−14 and ν = π/8.

Mentions: Jin et al.37 showed that in the sling-shot motion bacteria change between slow and fast modes, and that while the slow motion is directional, the fast mode (jumps) is often associated with substantial rotation. After obtaining long-time spatially resolved trajectories from both, the experiments and the simulations, we decomposed the trajectories into slow and fast modes of motion in a similar manner as has been done in ref. 37. Jumps are rare events, however, due to the substantial change of the cell position and direction during a jump, they make an important impact on the overall motion. In the simulations we typically observe clearly distinguishable slow and fast modes with an order of magnitude difference in the speed (Fig. 4). As assumed in ref. 37, the fast modes are correlated with the release of a bound pilus. However, only the release events associated with high tension in the filaments lead to fast jumps.


Emergence of complex behavior in pili-based motility in early stages of P. aeruginosa surface adaptation
Slow and fast modes.(a) Part of a trajectory from computer simulations. Red dots indicate pilus-release events, blue arrows point on fast jumps, with above-threshold velocity of 0.07 μm/s. Jumps always occur after a release, however not all the release event result in a jump. (b) Time evolution of the x-coordinate and its time derivative. The parameters used here are KRel = 130 s−1, KAd = 5 s−1, ka = 10−14 and ν = π/8.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385500&req=5

f4: Slow and fast modes.(a) Part of a trajectory from computer simulations. Red dots indicate pilus-release events, blue arrows point on fast jumps, with above-threshold velocity of 0.07 μm/s. Jumps always occur after a release, however not all the release event result in a jump. (b) Time evolution of the x-coordinate and its time derivative. The parameters used here are KRel = 130 s−1, KAd = 5 s−1, ka = 10−14 and ν = π/8.
Mentions: Jin et al.37 showed that in the sling-shot motion bacteria change between slow and fast modes, and that while the slow motion is directional, the fast mode (jumps) is often associated with substantial rotation. After obtaining long-time spatially resolved trajectories from both, the experiments and the simulations, we decomposed the trajectories into slow and fast modes of motion in a similar manner as has been done in ref. 37. Jumps are rare events, however, due to the substantial change of the cell position and direction during a jump, they make an important impact on the overall motion. In the simulations we typically observe clearly distinguishable slow and fast modes with an order of magnitude difference in the speed (Fig. 4). As assumed in ref. 37, the fast modes are correlated with the release of a bound pilus. However, only the release events associated with high tension in the filaments lead to fast jumps.

View Article: PubMed Central - PubMed

ABSTRACT

Pseudomonas aeruginosa move across surfaces by using multiple Type IV Pili (TFP), motorized appendages capable of force generation via linear extension/retraction cycles, to generate surface motions collectively known as twitching motility. Pseudomonas cells arrive at a surface with low levels of piliation and TFP activity, which both progressively increase as the cells sense the presence of a surface. At present, it is not clear how twitching motility emerges from these initial minimal conditions. Here, we build a simple model for TFP-driven surface motility without complications from viscous and solid friction on surfaces. We discover the unanticipated structural requirement that TFP motors need to have a minimal amount of effective angular rigidity in order for cells to perform the various classes of experimentally-observed motions. Moreover, a surprisingly small number of TFP are needed to recapitulate movement signatures associated with twitching: Two TFP can already produce movements reminiscent of recently observed slingshot type motion. Interestingly, jerky slingshot motions characteristic of twitching motility comprise the transition region between different types of observed crawling behavior in the dynamical phase diagram, such as self-trapped localized motion, 2-D diffusive exploration, and super-diffusive persistent motion.

No MeSH data available.