Not Just Going with the Flow: The Effects of Fluid Flow on Bacteria and Plankton

Wheeler, Jeanette D.; Secchi, Eleonora; Rusconi, Roberto; Stocker, Roman

doi:10.1146/annurev-cellbio-100818-125119

Cited by 102 publications

(69 citation statements)

References 122 publications

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“…Equating eqs. (30) and (31) therefore provides an implicit equation for θ * , which is dependent on the material viscosities through m(θ) and g(θ). This is an analytical result, and valid for any nematic-forming liquid.…”

Section: Analysis: Asymptotic Solutions For Large Pressure Gradient Omentioning

confidence: 99%

“…A number of authors have considered models of dilute suspension of active swimmers in a pressure gradient [25][26][27] and dense continuum models of channel flow, albeit in a tumbling nematic regime [28]. Others have reported experimental studies of similar systems [29], while there are also general reviews of the rheology of active fluids in [13,30,31]. In this paper we add to these previous investigations, considering a dense continuum model of an active fluid subjected to an external pressure gradient along a channel.…”

Section: Introductionmentioning

confidence: 99%

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Pressure-driven changes to spontaneous flow in active nematic liquid crystals

et al. 2020

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We consider the effects of a pressure gradient on the spontaneous flow of an active nematic liquid crystal in a channel, subject to planar anchoring and no-slip conditions on the boundaries of the channel. We employ a model based on the Ericksen-Leslie theory of nematics, with an additional active stress accounting for the activity of the fluid. By directly solving the flow equation, we consider an asymptotic solution for the director angle equation for large activity parameter values and predict the possible values of the director angle in the bulk of the channel. Through a numerical solution of the full nonlinear equations, we examine the effects of pressure on the branches of stable and unstable equilibria, some of which are disconnected from the no-flow state. In the absence of a pressure gradient, solutions are either symmetric or antisymmetric about the channel midpoint; these symmetries are changed by the pressure gradient. Considering the activity-pressure state space allows us to predict qualitatively the extent of each solution type and to show, for large enough pressure gradients, that a branch of non-trivial director angle solutions exists for all activity values.

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Section: Analysis: Asymptotic Solutions For Large Pressure Gradient Omentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pressure-driven changes to spontaneous flow in active nematic liquid crystals

et al. 2020

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“…An algal particle is surrounded by a sphere that is enriched in organic molecules leaked by the cell. This phycosphere is the important interface in which exchanges between phytoplankton and bacteria and their surroundings take place 41–43 . As the flow around the cell changes from laminar to turbulent, the phycosphere gets deformed until it turns into a web of filaments, see e.g.…”

Section: Discussionmentioning

confidence: 99%

Oscillations in the near-field feeding current of a calanoid copepod are useful for particle sensing

Giuffre

Hinow

Jiang

et al. 2019

Sci Rep

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Calanoid copepods are small crustaceans that constitute a major element of aquatic ecosystems. Key to their success is their feeding apparatus consisting of sensor-studded mouth appendages that are in constant motion. These appendages generate a feeding current to enhance the encounter probability with food items. Additionally, sensing enables the organism to determine the position and quality of food particles, and to alter the near-field flow to capture and manipulate the particles for ingestion or rejection. Here we observe a freely swimming copepod Leptodiaptomus sicilis in multiple perspectives together with suspended particles that allow us to analyse the flow field created by the animal. We observe a highly periodic motion of the mouth appendages that is mirrored in oscillations of nearby tracer particles. We propose that the phase shift between the fluid and the particle velocities is sufficient for mechanical detection of the particles entrained in the feeding current. Moreover, we propose that an immersed algal cell may benefit from the excitation by increased uptake of dissolved inorganic compounds.

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“…The oceanic flow fields and their interaction with phytoplankton entail a nearly continuous spectrum of motions and associated processes which range from global scale circulation to the smaller molecular adjustments and from ecosystems to individual cells (Figure 1). The appearance and effects of flow change dramatically as one moves from the human scale, at which our intuition is trained, to the microscale, at which microorganisms experience flow (Kiørboe, 2008;Wheeler et al, 2019). Because the majority of phytoplankton are smaller than the smallest eddy size by one or two orders in magnitude, processes affecting individual cells develop in the viscous non-inertial realm where they displace with no turbulent drag (Purcell, 1977).…”

Section: Upscaling Effects Of the Microscopic Worldmentioning

confidence: 99%

Phytoplankton Orientation in a Turbulent Ocean: A Microscale Perspective

2020

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Phytoplankton are by definition autotrophic microorganisms that passively drift with fluid motion. Accordingly, the traditional view of a turbulence-homogenized phytoplankton distribution in the ocean, where cells randomly organize and interact, is deeply rooted in biological oceanography studies. However, increasing understanding of microscopic processes in the ocean is revealing a world of microscale patterns resulting from cell behaviors and fluid-cell interactions that challenges this vision. Autotrophic cells have developed active (i.e., flagella) and passive (i.e., morphological structures and vesicles) motility mechanisms that allow them different degrees of spatial control. Their complex interaction with the ocean physicochemical landscape commonly results in small-scale spatial heterogeneities and non-isotropic orientations that can strongly influence ecosystem level processes. Cell orientation, in particular, is fundamental for key biological functions such as sensing, metabolism, locomotion, chain formation, or sexual reproduction. Moreover, preferential alignment of elongated cells can modulate the propagation of light through the ocean and is fundamental for accurate interpretation of remote sensing data. Innovative observational and experimental techniques (e.g., in situ holography, laser diffractometry, etc.) allowing the subtle analysis of cell-fluid interactions are revealing that, at the microscopic level, organisms present well defined orientation and interaction patterns under prevalent conditions in the sea. Thus, the interplay of biology, fluid dynamics, and optics may shape, by means of anisotropic cell distributions, pivotal cross-scale aspects of phytoplankton ecology.

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Not Just Going with the Flow: The Effects of Fluid Flow on Bacteria and Plankton

Cited by 102 publications

References 122 publications

Pressure-driven changes to spontaneous flow in active nematic liquid crystals

Pressure-driven changes to spontaneous flow in active nematic liquid crystals

Oscillations in the near-field feeding current of a calanoid copepod are useful for particle sensing

Phytoplankton Orientation in a Turbulent Ocean: A Microscale Perspective

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