Species-dependent hydrodynamics of flagellum-tethered bacteria in early biofilm development

Bennett, Rachel R.; Lee, Calvin K.; Anda, Jaime de; Nealson, Kenneth H.; Yildiz, Fitnat H.; O’Toole, George A.; Wong, Gerard C. L.; Golestanian, Ramin

doi:10.1098/rsif.2015.0966

Cited by 25 publications

(39 citation statements)

References 33 publications

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“…The flagellar hook, which is the flexible joint between the cell body and the flagellum, has a spring constant k that penalizes deviations from the preferred angle between the cell body axis and the flagellum axis. 18 The flagellar motor exerts a torque τ at the base of the cell body, causing the flagellum to rotate relative to the body. The cell body is attached to the surface by fixing a point along the central long axis of the body 0.35 μ m away from the nonflagellated pole, and the body does not counter-rotate in response to the flagellum rotation.…”

Section: Resultsmentioning

confidence: 99%

“…Examples of flagellum-mediated surface dynamics include “swarming” 20–24 motility and “spinning” motility, 25–28 first seen in classic experiments in which Escherichia coli are tethered to a surface by their flagellum. 27,29 Recent mathematical modeling has even revealed species-specific hydrodynamic behavior 18 as well as synergistic dynamics due to pili and flagella interacting with surfaces in Vibrio cholerae . 12 However, detailed characterization of flagellum- driven motility behavior is complicated by the inherently 3D nature of the movement, the speed of which is too fast for conventional confocal microscopy to capture effectively.…”

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confidence: 99%

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High-Speed “4D” Computational Microscopy of Bacterial Surface Motility

Anda

Lee

et al. 2017

ACS Nano

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Bacteria exhibit surface motility modes that play pivotal roles in early-stage biofilm community development, such as type IV pili-driven “twitching” motility and flagellum-driven “spinning” and “swarming” motility. Appendage-driven motility is controlled by molecular motors, and analysis of surface motility behavior is complicated by its inherently 3D nature, the speed of which is too fast for confocal microscopy to capture. Here, we combine electromagnetic field computation and statistical image analysis to generate 3D movies close to a surface at 5 ms time resolution using conventional inverted microscopes. We treat each bacterial cell as a spherocylindrical lens and use finite element modeling to solve Maxwell’s equations and compute the diffracted light intensities associated with different angular orientations of the bacterium relative to the surface. By performing cross-correlation calculations between measured 2D microscopy images and a library of computed light intensities, we demonstrate that near-surface 3D movies of Pseudomonas aeruginosa translational and rotational motion are possible at high temporal resolution. Comparison between computational reconstructions and detailed hydrodynamic calculations reveals that P. aeruginosa act like low Reynolds number spinning tops with unstable orbits, driven by a flagellum motor with a torque output of ~2 pN μm. Interestingly, our analysis reveals that P. aeruginosa can undergo complex flagellum-driven dynamical behavior, including precession, nutation, and an unexpected taxonomy of surface motility mechanisms, including upright-spinning bacteria that diffuse laterally across the surface, and horizontal bacteria that follow helicoidal trajectories and exhibit superdiffusive movements parallel to the surface.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

High-Speed “4D” Computational Microscopy of Bacterial Surface Motility

Anda

Lee

et al. 2017

ACS Nano

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“…Our data suggest that a cAMP signal is produced as a result of FlhF-FimV interaction, and that cAMP modulates reversal frequency and speed of the flagellar motor in a MotAB-dependent manner. We speculate that MotAB may be recruited back to the flagellum in this setting, leading to the observed changes in flagellar behavior which may help drive the bacteria toward the surface [47]. These events likely precede the cdG-dependent signaling cascade described by Jenal and colleagues, which requires MotAB for its initiation [14].…”

Section: Discussionmentioning

confidence: 64%

Modulation of Flagellar Rotation in Surface-Attached Bacteria: A Circuit for Rapid Surface-Sensing

Schniederberend

Johnston

Shine

et al. 2019

Preprint

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Attachment is a necessary first step in bacterial commitment to surface-associated behaviors that include colonization, biofilm formation, and host-directed virulence. The Gramnegative opportunistic pathogen Pseudomonas aeruginosa can initially attach to surfaces via its single polar flagellum. Although many bacteria quickly detach, some become irreversibly attached and express surface-associated structures, such as Type IV pili, and behaviors, including twitching motility and biofilm initiation. P. aeruginosa that lack the GTPase FlhF assemble a randomly placed flagellum that is motile; however, we observed that these mutant bacteria show defects in biofilm formation comparable to those seen for non-motile, aflagellate bacteria. This phenotype was associated with altered behavior of ∆flhF bacteria immediately following surfaceattachment. Forward and reverse genetic screens led to the discovery that FlhF interacts with FimV to control flagellar rotation at a surface, and implicated cAMP signaling in this pathway.Although cAMP controls many transcriptional programs in P. aeruginosa, the known targets of this second messenger were not required to modulate flagellar rotation in surface-attached bacteria. Instead, alterations in switching behavior of the motor appear to result from previously undescribed effects of cAMP on switch complex proteins and/or the motor-stators associated with them. Author SummaryAttachment to a surface often triggers programs of gene expression that alter the behavior, virulence and fitness of bacteria. Initial contact is usually mediated by surface exposed adhesins, such as flagella or pili/fimbriae, and there is much interest in how these structures might sense and respond to surface attachment. The human bacterial pathogen Pseudomonas aeruginosa usually contacts surfaces via its polar flagellum, the rotary motor that also powers bacterial swimming. We observed that wild-type bacteria quickly stopped rotating their flagellum after surface attachment, but that a mutant lacking the flagellar-associated protein FlhF did not. Using a combination of genetic approaches, we demonstrated that FlhF interacts with a component of the flagellar rotor (FliG) and with a polar scaffolding protein that positively regulates cAMP production (FimV) to stop flagellar rotation and thereby favor bacterial persistence at a surface. We provide evidence that the second messenger cAMP is the likely signal generated by flagellar-mediated surface attachment and show that cAMP is sufficient to alter the behavior of the flagellar motor.

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“…For the Δ pilA mutant (and to a much lesser extent in WT), we also observe detachment events with cells that did not have a labeled flagellum, which suggests that non-flagellum-mediated detachment events can also occur. To study how TFP can influence flagellum-mediated spinning and detachment, we adapt a previously developed hydrodynamic model (37). Simulations show that TFP activity (i.e., extension or retraction) can lead to changes in the cell body tilt angle relative to the surface.…”

Section: Resultsmentioning

confidence: 99%

“…If the bacterium does not spin, then the angle between the body and surface will stay at the (arbitrary) initial condition we have chosen in the model. We show time using units of seconds and a torque value of 2 pN μm (37).…”

Section: Resultsmentioning

confidence: 99%

Phenotypic differences in reversible attachment behavior reveal distinctP. aeruginosasurface colonization strategies

Lee

Vachier

Anda

et al. 2019

Preprint

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27Despite possessing the machinery to sense, adhere to, and proliferate on surfaces, it is commonly observed that bacteria 28initially have a difficult time attaching to a surface. Before forming a bacterial biofilm, planktonic bacteria exhibit a 29 random period of transient surface attachment known as "reversible attachment" which is poorly understood. Using 30 community tracking methods at single-cell resolution, we examine how reversible attachment progresses during initial 31 stages of surface sensing. Pseudomonas aeruginosa strains PAO1 and PA14, which exhibit similar exponential trends of 32 surface cell population increase, show unanticipated differences when the behavior of each cell was considered at the 33 full lineage level and interpreted using the unifying quantitative framework of an exactly solvable stochastic model. 34Reversible attachment comprises two regimes of behavior, processive and nonprocessive, corresponding to whether 35 cells of the lineage stay on the surface long enough to divide, or not, before detaching. Stark differences between PAO1 36 and PA14 in the processive regime of reversible attachment suggest the existence of two complementary surface 37 2 colonization strategies, which are roughly analogous to "immediate-" vs "deferred-gratification" in a prototypical 38 cognitive-affective processing system. PAO1 lineages commit relatively quickly to a surface compared to PA14 lineages. 39 PA14 lineages allow detaching cells to retain memory of the surface so that they are primed for improved subsequent 40 surface attachment. In fact, it is possible to identify motility suppression events in PA14 lineages in the process of 41 surface commitment. We hypothesize that these contrasting strategies are rooted in downstream differences between 42Wsp-based and Pil-Chp-based surface sensing systems. 43 Keywords 44Bacteria biofilms | Pseudomonas aeruginosa | Reversible attachment | Stochastic model | Surface sensing 45 Importance 46The initial pivotal phase of bacterial biofilm formation known as "reversible attachment," where cells undergo a period 47 of transient surface attachment, is at once universal and poorly understood. What is more, although we know that 48 reversible attachment culminates ultimately in irreversible attachment, it is not clear how reversible attachment 49 progresses phenotypically as bacterial surface sensing circuits fundamentally alters cellular behavior. We analyze diverse 50 observed bacterial behavior one family at a time (defined as a full lineage of cells related to one another by division) 51using a unifying stochastic model and show that it leads to new insights on the time evolution of reversible attachment. 52Our results unify apparently disparate findings in the literature regarding early events in biofilm formation by PAO1 and 53 PA14 strains. 54

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Species-dependent hydrodynamics of flagellum-tethered bacteria in early biofilm development

Cited by 25 publications

References 33 publications

High-Speed “4D” Computational Microscopy of Bacterial Surface Motility

High-Speed “4D” Computational Microscopy of Bacterial Surface Motility

Modulation of Flagellar Rotation in Surface-Attached Bacteria: A Circuit for Rapid Surface-Sensing

Phenotypic differences in reversible attachment behavior reveal distinctP. aeruginosasurface colonization strategies

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