Collective motion of micro-swimmers leads to the emergence of coherent macroscopic structures. In the case of diluted cultures of micro-organisms, a typical dotted pattern can spontaneously appear within a few minutes, even in the absence of external stimulus, a signature of bioconvection. However, we know little about the resilience of bioconvective plumes facing an environmental alteration. Here, we take advantage of the phototactic behaviour of the green micro-algae Chlamydomonas reinhardtii to perturb bioconvection with an asymmetric lightning. Our experiments demonstrate that plumes first disappear, leaving place for a new anisotropic structure at the illuminated wall. We characterise the dynamics of this rising pattern at various scales and propose a mechanism based on the physical properties of the micro-swimmers.
Le mouvement collectif de micro-nageurs peut générer des structures macroscopiques. Les plumes de bioconvection en sont un exemple : elles apparaissent spontanément dans les cultures diluées de micro-organismes. Cependant, l’impact de signaux extérieurs sur ces structures reste peu exploré. Dans cette étude, nous exploitons le comportement phototactique de micro-algues vertes, Chlamydomonas reinhardtii. Elles nagent préférentiellement vers l’une des parois, éclairée, ce qui introduit une asymétrie dans la dynamique. Nos expériences montrent tout d’abord que les plumes de bioconvection disparaissent. Puis, de nouvelles structures anisotropes émergent le long de la paroi. Nous analysons la dynamique de ces motifs à différentes échelles et proposons un mécanisme basé sur les propriétés physiques des micro-nageurs.
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Mots-clés : Hydrodynamique, instabilités, micro-nageur, matière active
Anaëlle Givaudan 1 ; Francesco Picella 1 ; Hélène de Maleprade 1
CC-BY 4.0
Anaëlle Givaudan; Francesco Picella; Hélène de Maleprade. Roll formation in a bio-active fluid. Comptes Rendus. Physique, Volume 27 (2026), pp. 7-16. doi: 10.5802/crphys.268
@article{CRPHYS_2026__27_G1_7_0,
author = {Ana\"elle Givaudan and Francesco Picella and H\'el\`ene de Maleprade},
title = {Roll formation in a bio-active fluid},
journal = {Comptes Rendus. Physique},
pages = {7--16},
year = {2026},
publisher = {Acad\'emie des sciences, Paris},
volume = {27},
doi = {10.5802/crphys.268},
language = {en},
}
[1] Light control of localized photobioconvection, Phys. Rev. Lett., Volume 123 (2019), 158101, 098103, 6 pages | DOI
[2] Advances in bioconvection, Ann. Rev. Fluid Mech., Volume 52 (2020) no. 1, pp. 449-476 | DOI
[3] Wavelengths of bioconvection patterns, J. Exp. Biol., Volume 200 (1997), pp. 1515-1526 | DOI
[4] Pattern formation in a suspension of swimming microorganisms: equations and stability theory, J. Fluid Mech., Volume 69 (1975), 043001, pp. 591-613 | DOI
[5] Multiphase flow handbook (Clayton T Crowe, ed.), CRC Press, 2005 | DOI
[6] Self-concentration and large-scale coherence in bacterial dynamics, Phys. Rev. Lett., Volume 93 (2004), 098103, 4 pages | Zbl | DOI
[7] Light-controlled flows in active fluids, Nat. Phys., Volume 13 (2017), pp. 306-312 | DOI
[8] Metabolic activity controls the emergence of coherent flows in microbial suspensions, Proc. Natl. Acad. Sci. USA, Volume 122 (2025) no. 4, e2413340122, 950, 8 pages | DOI
[9] Dynamically induced spatial segregation in multispecies bacterial bioconvection, Nat. Commun., Volume 16 (2025), 950, 13578, 13 pages | DOI
[10] Supplementary material to “Roll formation in a bio-active fluid”, 2026 | DOI | DOI
[11] Wavelength selection in gyrotactic bioconvection, Bull. Math. Biol., Volume 77 (2015), pp. 1166-1184 | DOI
[12] Reverse bioconvection of Chlamydomonas in the hyper-density medium, Biol. Sci. Space, Volume 24 (2010), pp. 145-152 | DOI
[13] Gravity-related behaviour in ciliates and flagellates, Cell biology and biotechnology in space (Augusto Cogoli, ed.) (Advances in Space Biology and Medicine), Elsevier, 2002 no. 8, pp. 59-75 | DOI
[14] Bioconvection, Fluid Dyn. Res., Volume 37 (2005) no. 1, jeb205989, pp. 1-20 | DOI
[15] Chlamydomonas in the Laboratory, The Chlamydomonas Sourcebook, Academic Press Inc. (2009), pp. 241-302 | DOI
[16] Evolution of bioconvection patterns in a culture of motile flagellates, Phys. Fluids, Volume 31 (1988) no. 4, pp. 764-775 | DOI
[17] Photo-bioconvection: towards light control of flows in active suspensions, Philos. Trans. R. Soc. Lond., Ser. A, Volume 378 (2020) no. 2179, 20190523 | DOI
[18] Co-operative and concentrative phenomena of swimming micro-organisms, Contemp. Phys., Volume 26 (1985) no. 2, pp. 147-166 | DOI
[19] Individual and collective fluid dynamics of swimming cells, J. Fluid Mech., Volume 173 (1986), e2413340122, pp. 191-205 | DOI
[20] Drastic reorganization of the bioconvection pattern of Chlamydomonas: quantitative analysis of the pattern transition response, J. Exp. Biol., Volume 216 (2013), pp. 4557-4566
[21] The shape effect of flagella is more important than bottom-heaviness on passive gravitactic orientation in Chlamydomonas reinhardtii, J. Exp. Biol., Volume 223 (2020) no. 5, jeb205989, 9 pages | DOI | MR
[22] Phototaxis of Chlamydomonas arises from a tuned adaptive photoresponse shared with multicellular Volvocine green algae, Phys. Rev. E, Volume 107 (2023), 014404, 25 pages | DOI
[23] A mathematical model of pattern formation by swimming microorganisms, J. Protozool., Volume 22 (1975), pp. 296-306 | DOI | MR
[24] Short-term memory effects in the phototactic behavior of microalgae, Soft Matter, Volume 20 (2024), 014404, pp. 3996-4006 | DOI
[25] Concerning pattern formation by free-swimming microorganisms, Am. Natur., Volume 86 (1952), pp. 325-329 | DOI
[26] “Bioconvection patterns” in cultures of free-swimming organisms, Science, Volume 133 (1961), 20190523, pp. 1766-1767 | DOI | MR
[27] Nonlinear phototaxis and instabilities in suspensions of light-seeking algae, Phys. Rev. Lett., Volume 128 (2022), 258101, 158101, 5 pages | DOI
[28] Localized bioconvection patterns and their initial state dependency in Euglena gracilis suspensions in an annular container, J. Phys. Soc. Japan, Volume 83 (2014) no. 4, 043001 | DOI
[29] Self-organisation and convection of confined magnetotactic bacteria, Sci. Rep., Volume 10 (2020), 13578, 258101, 9 pages | DOI
[30] Polygonal motion and adaptable phototaxis via flagellar beat switching in the microswimmer Euglena gracilis, Nat. Phys., Volume 14 (2018), pp. 1216-1222 | DOI
[31] VII. On the effect of gravity upon the movements and aggregation of Euglena viridis, Ehrb., and other micro-organisms, Philos. Trans. R. Soc. Lond., Ser. B, Volume 201 (1911), pp. 333-390 | DOI
[32] A tale of three taxes: photo-gyro-gravitactic bioconvection, J. Exp. Biol., Volume 214 (2011), pp. 2398-2408 | DOI
[33] Geotaxis in protozoa I. A propulsion-gravity model for tetrahymena (Ciliata), J. Theor. Biol., Volume 46 (1974), pp. 449-465 | DOI
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