An Adaptive Flagellar Photoresponse Determines the Dynamics of Accurate Phototactic Steering in<i>Chlamydomonas</i>

Leptos, Kyriacos C.; Chioccioli, Maurizio; Furlan, Silvano; Ai, Pesci; Goldstein, Raymond E.

doi:10.1101/254714

Cited by 14 publications

(24 citation statements)

References 24 publications

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“…We can discuss our findings in terms of what is known about the phototactic and photogyrotactic behaviour of microalgal suspensions. When the LED is switched on, the suspension responds visibly in seconds, similarly to what has been measured for populations responding to light from an optical fibre [23], and corresponding to the time scale for C. reinhardtii to perceive light and turn to swim towards it by controlling their flagellar beat [24]. Subsequent to this initial response, the suspension displays instabilities in cell concentration and flow.…”

Section: Discussionsupporting

confidence: 52%

“…In this study, we focus on how light can be used to control and concentrate a suspension of Chlamydomonas reinhardtii microalgae. The bias of swimming by light is known as phototaxis and is an adaptation that allows C. reinhardtii and other photosynthetic microorganisms to find optimal levels of light needed to grow [23,24]. Recent studies have demonstrated how exposing a suspension of microalgae to light can dramatically alter the patterns they form, and even generate new ones [25].…”

Section: Introductionmentioning

confidence: 99%

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Photogyrotactic Concentration of a Population of Swimming Microalgae Across a Porous Layer

Prakash

Croze

2021

Front. Phys.

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The light environment controls the swimming of microalgae through a light-seeking and avoiding behaviour, which is known as phototaxis. In this work, we exploit phototaxis to control the migration and concentration of populations of the soil microalga Chlamydomonas reinhardtii. By imaging a suspension of these microalgae in a cuvette illuminated from above by blue light, we study how phototaxis changes the stability of the suspension and demonstrate how a thin, porous layer at the top of the cuvette prevents phototaxing microalgae from sinking, leading to the up-concentration of the microalgae in the region above the porous layer. We discuss the potential implications of our findings for microalgae in biotechnological applications and the natural environment.

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Section: Discussionsupporting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Photogyrotactic Concentration of a Population of Swimming Microalgae Across a Porous Layer

Prakash

Croze

2021

Front. Phys.

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“…Chlamydomonas cells perform positive or negative phototaxis, depending on the nature of the stimulus [19,42]. Phototactic steering is associated with changes in both beat amplitude and frequency and is fine-tuned to the body rotation frequency [16,20,43]. In general, steering is accomplished by changing Ω [10,44], which in turn changes helix properties (radius, pitch, orientation).…”

Section: Figmentioning

confidence: 99%

Control of helical navigation by three-dimensional flagellar beating

Cortese

Wan

2020

Preprint

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Helical swimming is a ubiquitous strategy for motile cells to generate self-gradients for environmental sensing. The model biflagellate Chlamydomonas reinhardtii rotates at a constant 1 – 2 Hz as it swims, but the mechanism is unclear. Here, we show unequivocally that the rolling motion derives from a persistent, non-planar flagellar beat pattern. This is revealed by high-speed imaging and micromanipulation of live cells. We construct a fully-3D model to relate flagellar beating directly to the free-swimming trajectories. For realistic geometries, the model reproduces both the sense and magnitude of the axial rotation of live cells. We show that helical swimming requires further symmetry-breaking between the two flagella. These functional differences underlie all tactic responses, particularly phototaxis. We propose a control strategy by which cells steer towards or away from light by modulating the sign of biflagellar dominance.

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“…Most microorganisms respond to light by linking swimming speed to light intensity (photokinesis, [28]) and/or re-directing their motion towards or away from the light source (phototaxis, [29][30][31]). Although the physiological details underpinning these active re-sponses are often not completely understood [30][31][32][33], techniques employing light to precisely control the dynamics of swimming microorganisms are already emerging. Biological responses to light led to the development of genetically-engineered light-sensitive bacteria [34][35][36] used, for example, to power micron-size motors [23], and have even inspired the fabrication of light-reactive artificial swimmers [11,[37][38][39].…”

mentioning

confidence: 99%

“…2a). As the actinic light is switched on, phototactic cells start accumulating around the fibre, through a characteristic phototactic steering mechanism [33] based on an interplay between time-dependent stimulation of a light-sensitive organelle [53,54] and the ensuing flagellar response [55]. Phototaxis leads, within ∼ 10 s, to a ∼ 2 mm-wide region of high cell concentration [31].…”

mentioning

confidence: 99%