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Crockett WW, Shaw JO, Simpson C, Kempes CP. Physical constraints during Snowball Earth drive the evolution of multicellularity. Proc Biol Sci 2024; 291:20232767. [PMID: 38924758 PMCID: PMC11271684 DOI: 10.1098/rspb.2023.2767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 05/09/2024] [Indexed: 06/28/2024] Open
Abstract
Molecular and fossil evidence suggests that complex eukaryotic multicellularity evolved during the late Neoproterozoic era, coincident with Snowball Earth glaciations, where ice sheets covered most of the globe. During this period, environmental conditions-such as seawater temperature and the availability of photosynthetically active light in the oceans-likely changed dramatically. Such changes would have had significant effects on both resource availability and optimal phenotypes. Here, we construct and apply mechanistic models to explore (i) how environmental changes during Snowball Earth and biophysical constraints generated selective pressures, and (ii) how these pressures may have had differential effects on organisms with different forms of biological organization. By testing a series of alternative-and commonly debated-hypotheses, we demonstrate how multicellularity was likely acquired differently in eukaryotes and prokaryotes owing to selective differences on their size due to the biophysical and metabolic regimes they inhabit: decreasing temperatures and resource availability instigated by the onset of glaciations generated selective pressures towards smaller sizes in organisms in the diffusive regime and towards larger sizes in motile heterotrophs. These results suggest that changing environmental conditions during Snowball Earth glaciations gave multicellular eukaryotes an evolutionary advantage, paving the way for the complex multicellular lineages that followed.
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Affiliation(s)
- William W. Crockett
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Santa Fe Institute, Santa Fe, NM 87501, USA
| | | | - Carl Simpson
- Department of Geological Sciences and University of Colorado Museum of Natural History, University of Colorado, Boulder, CO 80309, USA
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2
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Ling F, Essock-Burns T, McFall-Ngai M, Katija K, Nawroth JC, Kanso E. Flow Physics Explains Morphological Diversity of Ciliated Organs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.02.12.528181. [PMID: 38168341 PMCID: PMC10760039 DOI: 10.1101/2023.02.12.528181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Organs that pump fluids by the coordinated beat of motile cilia through the lumen are integral to animal physiology. Such organs include the human airways, brain ventricles, and reproductive tracts. Although cilia organization and duct morphology vary drastically in the animal kingdom, ducts are typically classified as either carpet or flame designs. The reason behind this dichotomy and how duct design relates to fluid pumping remain unclear. Here, we demonstrate that two structural parameters -- lumen diameter and cilia-to-lumen ratio -- organize the observed duct diversity into a continuous spectrum that connects carpets to flames across all animal phyla. Using a unified fluid model, we show that carpet and flame designs maximize flow rate and pressure generation, respectively. We propose that convergence of ciliated organ designs follows functional constraints rather than phylogenetic distance, along with universal design rules for ciliary pumps.
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3
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Larson BT. Perspectives on Principles of Cellular Behavior from the Biophysics of Protists. Integr Comp Biol 2023; 63:1405-1421. [PMID: 37496203 PMCID: PMC10755178 DOI: 10.1093/icb/icad106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 07/14/2023] [Accepted: 07/17/2023] [Indexed: 07/28/2023] Open
Abstract
Cells are the fundamental unit of biological organization. Although it may be easy to think of them as little more than the simple building blocks of complex organisms such as animals, single cells are capable of behaviors of remarkable apparent sophistication. This is abundantly clear when considering the diversity of form and function among the microbial eukaryotes, the protists. How might we navigate this diversity in the search for general principles of cellular behavior? Here, we review cases in which the intensive study of protists from the perspective of cellular biophysics has driven insight into broad biological questions of morphogenesis, navigation and motility, and decision making. We argue that applying such approaches to questions of evolutionary cell biology presents rich, emerging opportunities. Integrating and expanding biophysical studies across protist diversity, exploiting the unique characteristics of each organism, will enrich our understanding of general underlying principles.
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Affiliation(s)
- Ben T Larson
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA
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4
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Cornwallis CK, Svensson-Coelho M, Lindh M, Li Q, Stábile F, Hansson LA, Rengefors K. Single-cell adaptations shape evolutionary transitions to multicellularity in green algae. Nat Ecol Evol 2023; 7:889-902. [PMID: 37081145 PMCID: PMC10250200 DOI: 10.1038/s41559-023-02044-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 03/22/2023] [Indexed: 04/22/2023]
Abstract
The evolution of multicellular life has played a pivotal role in shaping biological diversity. However, we know surprisingly little about the natural environmental conditions that favour the formation of multicellular groups. Here we experimentally examine how key environmental factors (predation, nitrogen and water turbulence) combine to influence multicellular group formation in 35 wild unicellular green algae strains (19 Chlorophyta species). All environmental factors induced the formation of multicellular groups (more than four cells), but there was no evidence this was adaptive, as multicellularity (% cells in groups) was not related to population growth rate under any condition. Instead, population growth was related to extracellular matrix (ECM) around single cells and palmelloid formation, a unicellular life-cycle stage where two to four cells are retained within a mother-cell wall after mitosis. ECM production increased with nitrogen levels resulting in more cells being in palmelloids and higher rates of multicellular group formation. Examining the distribution of 332 algae species across 478 lakes monitored over 55 years, showed that ECM and nitrogen availability also predicted patterns of obligate multicellularity in nature. Our results highlight that adaptations of unicellular organisms to cope with environmental challenges may be key to understanding evolutionary routes to multicellular life.
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Affiliation(s)
| | | | - Markus Lindh
- Swedish Meteorological and Hydrological Institute, Västra Frölunda, Sweden
| | - Qinyang Li
- Department of Biology, Lund University, Lund, Sweden
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Shekhar S, Guo H, Colin SP, Marshall W, Kanso E, Costello JH. Cooperative hydrodynamics accompany multicellular-like colonial organization in the unicellular ciliate Stentor. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.10.523506. [PMID: 36711609 PMCID: PMC9882025 DOI: 10.1101/2023.01.10.523506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Evolution of multicellularity from early unicellular ancestors is arguably one of the most important transitions since the origin of life1,2. Multicellularity is often associated with higher nutrient uptake3, better defense against predation, cell specialization and better division of labor4. While many single-celled organisms exhibit both solitary and colonial existence3,5,6, the organizing principles governing the transition and the benefits endowed are less clear. Using the suspension-feeding unicellular protist Stentor coeruleus, we show that hydrodynamic coupling between proximal neighbors results in faster feeding flows that depend on the separation between individuals. Moreover, we find that the accrued benefits in feeding current enhancement are typically asymmetric- individuals with slower solitary currents gain more from partnering than those with faster currents. We find that colony-formation is ephemeral in Stentor and individuals in colonies are highly dynamic unlike other colony-forming organisms like Volvox carteri 3. Our results demonstrate benefits endowed by the colonial organization in a simple unicellular organism and can potentially provide fundamental insights into the selective forces favoring early evolution of multicellular organization.
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Affiliation(s)
- Shashank Shekhar
- Department of Physics, Emory University, Atlanta, USA
- Whitman Center, Marine Biological Laboratory, Woods Hole, USA
- Department of Cell Biology, Emory University, Atlanta, USA
| | - Hanliang Guo
- Department of Mathematics and Computer Science, Ohio Wesleyan University, Delaware, USA
| | - Sean P. Colin
- Whitman Center, Marine Biological Laboratory, Woods Hole, USA
- Department of Marine Biology and Environmental Science, Roger Williams University, Bristol, USA
| | - Wallace Marshall
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, USA
| | - Eva Kanso
- Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, USA
| | - John H. Costello
- Whitman Center, Marine Biological Laboratory, Woods Hole, USA
- Department of Biology, Providence College, Providence, USA
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6
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Selective drivers of simple multicellularity. Curr Opin Microbiol 2022; 67:102141. [PMID: 35247708 DOI: 10.1016/j.mib.2022.102141] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 12/21/2022]
Abstract
In order to understand the evolution of multicellularity, we must understand how and why selection favors the first steps in this process: the evolution of simple multicellular groups. Multicellularity has evolved many times in independent lineages with fundamentally different ecologies, yet no work has yet systematically examined these diverse selective drivers. Here we review recent developments in systematics, comparative biology, paleontology, synthetic biology, theory, and experimental evolution, highlighting ten selective drivers of simple multicellularity. Our survey highlights the many ecological opportunities available for simple multicellularity, and stresses the need for additional work examining how these first steps impact the subsequent evolution of complex multicellularity.
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Genome sequencing of the multicellular alga Astrephomene provides insights into convergent evolution of germ-soma differentiation. Sci Rep 2021; 11:22231. [PMID: 34811380 PMCID: PMC8608804 DOI: 10.1038/s41598-021-01521-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 10/29/2021] [Indexed: 01/27/2023] Open
Abstract
Germ-soma differentiation evolved independently in many eukaryotic lineages and contributed to complex multicellular organizations. However, the molecular genetic bases of such convergent evolution remain unresolved. Two multicellular volvocine green algae, Volvox and Astrephomene, exhibit convergent evolution of germ-soma differentiation. The complete genome sequence is now available for Volvox, while genome information is scarce for Astrephomene. Here, we generated the de novo whole genome sequence of Astrephomene gubernaculifera and conducted RNA-seq analysis of isolated somatic and reproductive cells. In Volvox, tandem duplication and neofunctionalization of the ancestral transcription factor gene (RLS1/rlsD) might have led to the evolution of regA, the master regulator for Volvox germ-soma differentiation. However, our genome data demonstrated that Astrephomene has not undergone tandem duplication of the RLS1/rlsD homolog or acquisition of a regA-like gene. Our RNA-seq analysis revealed the downregulation of photosynthetic and anabolic gene expression in Astrephomene somatic cells, as in Volvox. Among genes with high expression in somatic cells of Astrephomene, we identified three genes encoding putative transcription factors, which may regulate somatic cell differentiation. Thus, the convergent evolution of germ-soma differentiation in the volvocine algae may have occurred by the acquisition of different regulatory circuits that generate a similar division of labor.
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Abstract
Nutrient acquisition is a challenge that often favors small individual phytoplanktors because they are superior competitors at low nutrient levels. An alternative to these individual solutions is the union of different species into consortia that rely upon division of labor for competitive advantage. Although planktonic epibionts are well documented, the advantages of consortia for the larger host cells have remained unclear. Here, we demonstrate that attached ciliates dramatically increase the flux of dissolved nutrients to host phytoplankton cells, providing the necessary conditions for large diatoms to thrive in oligotrophic ecosystems. This demonstrates that unions between different species can substantially increase rates of nutrient flow to host cells and provides an alternative to sinking for protists living in low-nutrient conditions. Nutrient acquisition is crucial for oceanic microbes, and competitive solutions to solve this challenge have evolved among a range of unicellular protists. However, solitary solutions are not the only approach found in natural populations. A diverse array of oceanic protists form temporary or even long-lasting attachments to other protists and marine aggregates. Do these planktonic consortia provide benefits to their members? Here, we use empirical and modeling approaches to evaluate whether the relationship between a large centric diatom, Coscinodiscus wailesii, and a ciliate epibiont, Pseudovorticella coscinodisci, provides nutrient flux benefits to the host diatom. We find that fluid flows generated by ciliary beating can increase nutrient flux to a diatom cell surface four to 10 times that of a still cell without ciliate epibionts. This cosmopolitan species of diatom does not form consortia in all environments but frequently joins such consortia in nutrient-depleted waters. Our results demonstrate that symbiotic consortia provide a cooperative alternative of comparable or greater magnitude to sinking for enhancement of nutrient acquisition in challenging environments.
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The evolution of convex trade-offs enables the transition towards multicellularity. Nat Commun 2021; 12:4222. [PMID: 34244514 PMCID: PMC8270964 DOI: 10.1038/s41467-021-24503-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 06/17/2021] [Indexed: 11/13/2022] Open
Abstract
The evolutionary transition towards multicellular life often involves growth in groups of undifferentiated cells followed by differentiation into soma and germ-like cells. Theory predicts that germ soma differentiation is facilitated by a convex trade-off between survival and reproduction. However, this has never been tested and these transitions remain poorly understood at the ecological and genetic level. Here, we study the evolution of cell groups in ten isogenic lines of the unicellular green algae Chlamydomonas reinhardtii with prolonged exposure to a rotifer predator. We confirm that growth in cell groups is heritable and characterized by a convex trade-off curve between reproduction and survival. Identical mutations evolve in all cell group isolates; these are linked to survival and reducing associated cell costs. Overall, we show that just 500 generations of predator selection were sufficient to lead to a convex trade-off and incorporate evolved changes into the prey genome. Multicellularity is a major evolutionary transition that remains poorly characterized at the ecological and genetic level. Exposing unicellular green algae to a rotifer predator showed that just 500 generations of predator selection were sufficient to lead to a convex trade-off and incorporate evolved changes into the prey genome.
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10
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Swimming microorganisms acquire optimal efficiency with multiple cilia. Proc Natl Acad Sci U S A 2020; 117:30201-30207. [PMID: 33199601 DOI: 10.1073/pnas.2011146117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Planktonic microorganisms are ubiquitous in water, and their population dynamics are essential for forecasting the behavior of global aquatic ecosystems. Their population dynamics are strongly affected by these organisms' motility, which is generated by their hair-like organelles, called cilia or flagella. However, because of the complexity of ciliary dynamics, the precise role of ciliary flow in microbial life remains unclear. Here, we have used ciliary hydrodynamics to show that ciliates acquire the optimal propulsion efficiency. We found that ciliary flow highly resists an organism's propulsion and that the swimming velocity rapidly decreases with body size, proportional to the power of minus two. Accordingly, the propulsion efficiency decreases as the cube of body length. By increasing the number of cilia, however, efficiency can be significantly improved, up to 100-fold. We found that there exists an optimal number density of cilia, which provides the maximum propulsion efficiency for all ciliates. The propulsion efficiency in this case decreases inversely proportionally to body length. Our estimated optimal density of cilia corresponds to those of actual microorganisms, including species of ciliates and microalgae, which suggests that now-existing motile ciliates and microalgae have survived by acquiring the optimal propulsion efficiency. These conclusions are helpful for better understanding the ecology of microorganisms, such as the energetic costs and benefits of multicellularity in Volvocaceae, as well as for the optimal design of artificial microswimmers.
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11
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Olejarz J, Kaveh K, Veller C, Nowak MA. Selection for synchronized cell division in simple multicellular organisms. J Theor Biol 2018; 457:170-179. [PMID: 30172691 PMCID: PMC6169303 DOI: 10.1016/j.jtbi.2018.08.038] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 07/30/2018] [Accepted: 08/29/2018] [Indexed: 02/08/2023]
Abstract
The evolution of multicellularity was a major transition in the history of life on earth. Conditions under which multicellularity is favored have been studied theoretically and experimentally. But since the construction of a multicellular organism requires multiple rounds of cell division, a natural question is whether these cell divisions should be synchronous or not. We study a population model in which there compete simple multicellular organisms that grow by either synchronous or asynchronous cell divisions. We demonstrate that natural selection can act differently on synchronous and asynchronous cell division, and we offer intuition for why these phenotypes are generally not neutral variants of each other.
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Affiliation(s)
- Jason Olejarz
- Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA.
| | - Kamran Kaveh
- Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA.
| | - Carl Veller
- Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
| | - Martin A Nowak
- Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA; Department of Mathematics, Harvard University, Cambridge, MA 02138, USA.
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12
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Rebolleda-Gómez M, Travisano M. The Cost of Being Big: Local Competition, Importance of Dispersal, and Experimental Evolution of Reversal to Unicellularity. Am Nat 2018; 192:731-744. [PMID: 30444659 DOI: 10.1086/700095] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Multicellularity provides multiple benefits. Nonetheless, unicellularity is ubiquitous, and there have been multiple cases of evolutionary reversal to a unicellular organization. In this article, we explore some of the costs of multicellularity as well as the possibility and dynamics of evolutionary reversals to unicellularity. We hypothesize that recently evolved multicellular organisms would face a high cost of increased competition for local resources in spatially structured environments because of larger size and increased cell densities. To test this hypothesis we conducted competition assays, computer simulations, and selection experiments using isolates of Saccharomyces cerevisiae that recently evolved multicellularity. In well-mixed environments, multicellular isolates had lower growth rates relative to their unicellular ancestor because of limitations of space and resource acquisition. In structured environments with localized resources, cells in both multicellular and unicellular isolates grew at a similar rate. Despite similar growth, higher local density of cells in multicellular groups led to increased competition and higher fitness costs in spatially structured environments. In structured environments all of the multicellular isolates rapidly evolved a predominantly unicellular life cycle, while in well-mixed environments reversal was more gradual. Taken together, these results suggest that a lack of dispersal, leading to higher local competition, might have been one of the main constraints in the evolution of early multicellular forms.
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13
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Bornens M. Cell polarity: having and making sense of direction-on the evolutionary significance of the primary cilium/centrosome organ in Metazoa. Open Biol 2018; 8:180052. [PMID: 30068565 PMCID: PMC6119866 DOI: 10.1098/rsob.180052] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/05/2018] [Indexed: 12/13/2022] Open
Abstract
Cell-autonomous polarity in Metazoans is evolutionarily conserved. I assume that permanent polarity in unicellular eukaryotes is required for cell motion and sensory reception, integration of these two activities being an evolutionarily constrained function. Metazoans are unique in making cohesive multicellular organisms through complete cell divisions. They evolved a primary cilium/centrosome (PC/C) organ, ensuring similar functions to the basal body/flagellum of unicellular eukaryotes, but in different cells, or in the same cell at different moments. The possibility that this innovation contributed to the evolution of individuality, in being instrumental in the early specification of the germ line during development, is further discussed. Then, using the example of highly regenerative organisms like planarians, which have lost PC/C organ in dividing cells, I discuss the possibility that part of the remodelling necessary to reach a new higher-level unit of selection in multi-cellular organisms has been triggered by conflicts among individual cell polarities to reach an organismic polarity. Finally, I briefly consider organisms with a sensorimotor organ like the brain that requires exceedingly elongated polarized cells for its activity. I conclude that beyond critical consequences for embryo development, the conservation of cell-autonomous polarity in Metazoans had far-reaching implications for the evolution of individuality.
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Affiliation(s)
- Michel Bornens
- Institut Curie, PSL Research University, CNRS - UMR 144, 75005 Paris, France
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14
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The effects of marine eukaryote evolution on phosphorus, carbon and oxygen cycling across the Proterozoic-Phanerozoic transition. Emerg Top Life Sci 2018; 2:267-278. [PMID: 32412617 PMCID: PMC7289021 DOI: 10.1042/etls20170156] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 04/27/2018] [Accepted: 05/01/2018] [Indexed: 12/03/2022]
Abstract
A ‘Neoproterozoic oxygenation event’ is widely invoked as a causal factor in animal evolution, and often attributed to abiotic causes such as post-glacial pulses of phosphorus weathering. However, recent evidence suggests a series of transient ocean oxygenation events ∼660–520 Ma, which do not fit the simple model of a monotonic rise in atmospheric oxygen (pO2). Hence, we consider mechanisms by which the evolution of marine eukaryotes, coupled with biogeochemical and ecological feedbacks, potentially between alternate stable states, could have caused changes in ocean carbon cycling and redox state, phosphorus cycling and atmospheric pO2. We argue that the late Tonian ocean ∼750 Ma was dominated by rapid microbial cycling of dissolved organic matter (DOM) with elevated nutrient (P) levels due to inefficient removal of organic matter to sediments. We suggest the abrupt onset of the eukaryotic algal biomarker record ∼660–640 Ma was linked to an escalation of protozoan predation, which created a ‘biological pump’ of sinking particulate organic matter (POM). The resultant transfer of organic carbon (Corg) and phosphorus to sediments was strengthened by subsequent eukaryotic innovations, including the advent of sessile benthic animals and mobile burrowing animals. Thus, each phase of eukaryote evolution tended to lower P levels and oxygenate the ocean on ∼104 year timescales, but by decreasing Corg/P burial ratios, tended to lower atmospheric pO2 and deoxygenate the ocean again on ∼106 year timescales. This can help explain the transient nature and ∼106 year duration of oceanic oxygenation events through the Cryogenian–Ediacaran–Cambrian.
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16
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Pedley TJ, Brumley DR, Goldstein RE. Squirmers with swirl: a model for Volvox swimming. JOURNAL OF FLUID MECHANICS 2016; 798:165-186. [PMID: 27795576 PMCID: PMC5070036 DOI: 10.1017/jfm.2016.306] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 04/13/2016] [Accepted: 04/24/2016] [Indexed: 05/08/2023]
Abstract
Colonies of the green alga Volvox are spheres that swim through the beating of pairs of flagella on their surface somatic cells. The somatic cells themselves are mounted rigidly in a polymeric extracellular matrix, fixing the orientation of the flagella so that they beat approximately in a meridional plane, with axis of symmetry in the swimming direction, but with a roughly [Formula: see text] azimuthal offset which results in the eponymous rotation of the colonies about a body-fixed axis. Experiments on colonies of Volvox carteri held stationary on a micropipette show that the beating pattern takes the form of a symplectic metachronal wave (Brumley et al. Phys. Rev. Lett., vol. 109, 2012, 268102). Here we extend the Lighthill/Blake axisymmetric, Stokes-flow model of a free-swimming spherical squirmer (Lighthill Commun. Pure Appl. Maths, vol. 5, 1952, pp. 109-118; Blake J. Fluid Mech., vol. 46, 1971b, pp. 199-208) to include azimuthal swirl. The measured kinematics of the metachronal wave for 60 different colonies are used to calculate the coefficients in the eigenfunction expansions and hence predict the mean swimming speeds and rotation rates, proportional to the square of the beating amplitude, as functions of colony radius. As a test of the squirmer model, the results are compared with measurements (Drescher et al. Phys. Rev. Lett., vol. 102, 2009, 168101) of the mean swimming speeds and angular velocities of a different set of 220 colonies, also given as functions of colony radius. The predicted variation with radius is qualitatively correct, but the model underestimates both the mean swimming speed and the mean angular velocity unless the amplitude of the flagellar beat is taken to be larger than previously thought. The reasons for this discrepancy are discussed.
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Affiliation(s)
- T. J. Pedley
- Department of Applied Mathematics and Theoretical Physics,
University of Cambridge, Centre for Mathematical
Sciences, Wilberforce Road, Cambridge CB3
0WA, UK
| | - D. R. Brumley
- Ralph M. Parsons Laboratory, Department of Civil and
Environmental Engineering, Massachusetts Institute of
Technology, Cambridge, MA 02139,
USA
- Department of Civil, Environmental and Geomatic Engineering,
ETH Zurich, 8093 Zurich,
Switzerland
| | - R. E. Goldstein
- Department of Applied Mathematics and Theoretical Physics,
University of Cambridge, Centre for Mathematical
Sciences, Wilberforce Road, Cambridge CB3
0WA, UK
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17
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Barsanti L, Coltelli P, Evangelista V, Frassanito AM, Gualtieri P. Swimming patterns of the quadriflagellate Tetraflagellochloris mauritanica (Chlamydomonadales, Chlorophyceae). JOURNAL OF PHYCOLOGY 2016; 52:209-218. [PMID: 27037586 DOI: 10.1111/jpy.12384] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 12/04/2015] [Indexed: 06/05/2023]
Abstract
Chlamydomonadales are elective subjects for the investigation of the problems related to locomotion and transport in biological fluid dynamics, whose resolution could enhance searching efficiency and assist in the avoidance of dangerous environments. In this paper, we elucidate the swimming behavior of Tetraflagellochloris mauritanica, a unicellular-multicellular alga belonging to the order Chlamydomonadales. This quadriflagellate alga has a complex swimming motion consisting of alternating swimming phases connected by in-place random reorientations and resting phases. It is capable of both forward and backward swimming, both being normal modes of swimming. The complex swimming behavior resembles the run-and-tumble motion of peritrichous bacteria, with in-place reorientation taking the place of tumbles. In the forward swimming, T. mauritanica shows a very efficient flagellar beat, with undulatory retrograde waves that run along the flagella to their tip. In the backward swimming, the flagella show a nonstereotypical synchronization mode, with a pattern that does not fit any of the modes present in the other Chlamydomonadales so far investigated.
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Affiliation(s)
- Laura Barsanti
- Istituto di Biofisica, CNR, Via Moruzzi 1, Pisa, 56124, Italy
| | - Primo Coltelli
- Istituto di Scienza e Tecnologia Informazione, CNR, Via Moruzzi 1, Pisa, 56124, Italy
| | | | | | - Paolo Gualtieri
- Istituto di Biofisica, CNR, Via Moruzzi 1, Pisa, 56124, Italy
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18
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Brumley DR, Polin M, Pedley TJ, Goldstein RE. Metachronal waves in the flagellar beating of Volvox and their hydrodynamic origin. J R Soc Interface 2016; 12:20141358. [PMID: 26040592 PMCID: PMC4528573 DOI: 10.1098/rsif.2014.1358] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Groups of eukaryotic cilia and flagella are capable of coordinating their beating over large scales, routinely exhibiting collective dynamics in the form of metachronal waves. The origin of this behaviour—possibly influenced by both mechanical interactions and direct biological regulation—is poorly understood, in large part due to a lack of quantitative experimental studies. Here we characterize in detail flagellar coordination on the surface of the multicellular alga Volvox carteri, an emerging model organism for flagellar dynamics. Our studies reveal for the first time that the average metachronal coordination observed is punctuated by periodic phase defects during which synchrony is partial and limited to specific groups of cells. A minimal model of hydrodynamically coupled oscillators can reproduce semi-quantitatively the characteristics of the average metachronal dynamics, and the emergence of defects. We systematically study the model's behaviour by assessing the effect of changing intrinsic rotor characteristics, including oscillator stiffness and the nature of their internal driving force, as well as their geometric properties and spatial arrangement. Our results suggest that metachronal coordination follows from deformations in the oscillators' limit cycles induced by hydrodynamic stresses, and that defects result from sufficiently steep local biases in the oscillators' intrinsic frequencies. Additionally, we find that random variations in the intrinsic rotor frequencies increase the robustness of the average properties of the emergent metachronal waves.
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Affiliation(s)
- Douglas R Brumley
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Marco Polin
- Physics Department, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Timothy J Pedley
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
| | - Raymond E Goldstein
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
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Watson RA, Mills R, Buckley CL, Kouvaris K, Jackson A, Powers ST, Cox C, Tudge S, Davies A, Kounios L, Power D. Evolutionary Connectionism: Algorithmic Principles Underlying the Evolution of Biological Organisation in Evo-Devo, Evo-Eco and Evolutionary Transitions. Evol Biol 2015; 43:553-581. [PMID: 27932852 PMCID: PMC5119841 DOI: 10.1007/s11692-015-9358-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 10/31/2015] [Indexed: 12/16/2022]
Abstract
The mechanisms of variation, selection and inheritance, on which evolution by natural selection depends, are not fixed over evolutionary time. Current evolutionary biology is increasingly focussed on understanding how the evolution of developmental organisations modifies the distribution of phenotypic variation, the evolution of ecological relationships modifies the selective environment, and the evolution of reproductive relationships modifies the heritability of the evolutionary unit. The major transitions in evolution, in particular, involve radical changes in developmental, ecological and reproductive organisations that instantiate variation, selection and inheritance at a higher level of biological organisation. However, current evolutionary theory is poorly equipped to describe how these organisations change over evolutionary time and especially how that results in adaptive complexes at successive scales of organisation (the key problem is that evolution is self-referential, i.e. the products of evolution change the parameters of the evolutionary process). Here we first reinterpret the central open questions in these domains from a perspective that emphasises the common underlying themes. We then synthesise the findings from a developing body of work that is building a new theoretical approach to these questions by converting well-understood theory and results from models of cognitive learning. Specifically, connectionist models of memory and learning demonstrate how simple incremental mechanisms, adjusting the relationships between individually-simple components, can produce organisations that exhibit complex system-level behaviours and improve the adaptive capabilities of the system. We use the term "evolutionary connectionism" to recognise that, by functionally equivalent processes, natural selection acting on the relationships within and between evolutionary entities can result in organisations that produce complex system-level behaviours in evolutionary systems and modify the adaptive capabilities of natural selection over time. We review the evidence supporting the functional equivalences between the domains of learning and of evolution, and discuss the potential for this to resolve conceptual problems in our understanding of the evolution of developmental, ecological and reproductive organisations and, in particular, the major evolutionary transitions.
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Affiliation(s)
- Richard A. Watson
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Rob Mills
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisbon, Lisbon, Portugal
| | - C. L. Buckley
- School of Engineering and Informatics, University of Sussex, Falmer, UK
| | - Kostas Kouvaris
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
| | - Adam Jackson
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
| | | | - Chris Cox
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
| | - Simon Tudge
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
| | - Adam Davies
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
| | - Loizos Kounios
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
| | - Daniel Power
- Agents, Interactions and Complexity, ECS, University of Southampton, Southampton, UK
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20
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Abstract
Organisms show a remarkable range of sizes, yet the dimensions of a single cell rarely exceed 100 µm. While the physical and biological origins of this constraint remain poorly understood, exceptions to this rule give valuable insights. A well-known counterexample is the aquatic plant Chara, whose cells can exceed 10 cm in length and 1 mm in diameter. Two spiralling bands of molecular motors at the cell periphery drive the cellular fluid up and down at speeds up to 100 µm s(-1), motion that has been hypothesized to mitigate the slowness of metabolite transport on these scales and to aid in homeostasis. This is the most organized instance of a broad class of continuous motions known as 'cytoplasmic streaming', found in a wide range of eukaryotic organisms-algae, plants, amoebae, nematodes and flies-often in unusually large cells. In this overview of the physics of this phenomenon, we examine the interplay between streaming, transport and cell size and discuss the possible role of self-organization phenomena in establishing the observed patterns of streaming.
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Affiliation(s)
- Raymond E. Goldstein
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
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21
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Goldstein RE. Green Algae as Model Organisms for Biological Fluid Dynamics. ANNUAL REVIEW OF FLUID MECHANICS 2015; 47:343-375. [PMID: 26594068 PMCID: PMC4650200 DOI: 10.1146/annurev-fluid-010313-141426] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In the past decade the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimetres), their geometric regularity, the ease with which they can be cultured and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms.
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Affiliation(s)
- Raymond E. Goldstein
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
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Hayashi Y, Sugawara K. Simultaneous coupling of phototaxis and electrotaxis in Volvox algae. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:042714. [PMID: 24827285 DOI: 10.1103/physreve.89.042714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Indexed: 06/03/2023]
Abstract
In nature, living creatures are affected by several stimuli simultaneously. The response of living creatures to stimuli is called taxis. In order to reveal the principles of taxis behavior in response to complex stimuli, we simultaneously applied photostimulation and electric stimulation perpendicularly to a Volvox algae solution. The probability distribution of the swimming direction showed that a large population of swimming cells moved in a direction that was the result of the composition of phototaxis and electrotaxis. More surprisingly, we uncovered the coupling of signs of taxis, i.e., coupling of phototaxis and electrotaxis induced positive electrotaxis, which did not emerge in the single stimulation experiments. We qualitatively explained the coupling of taxis based on the polarization of the swimming cells induced by the simultaneous photo- and electric stimulation.
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Affiliation(s)
- Yoshikatsu Hayashi
- Brain Embodiment Laboratory, School of Systems Engineering, University of Reading, PO Box 225, Whiteknights, Reading RG6 6AY, United Kingdom
| | - Ken Sugawara
- Department of Information Science, College of Liberal Arts, Tohoku Gakuin University, 2-1-1 Tenjinzawa, Izumi-ku, Sendai, Miyagi 981-3193, Japan
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23
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Ghisalberti M, Gold DA, Laflamme M, Clapham ME, Narbonne GM, Summons RE, Johnston DT, Jacobs DK. Canopy flow analysis reveals the advantage of size in the oldest communities of multicellular eukaryotes. Curr Biol 2014; 24:305-9. [PMID: 24462003 DOI: 10.1016/j.cub.2013.12.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 11/28/2013] [Accepted: 12/09/2013] [Indexed: 11/27/2022]
Abstract
VIDEO ABSTRACT At Mistaken Point, Newfoundland, Canada, rangeomorph "fronds" dominate the earliest (579-565 million years ago) fossil communities of large (0.1 to 2 m height) multicellular benthic eukaryotes. They lived in low-flow environments, fueled by uptake [1-3] of dissolved reactants (osmotrophy). However, prokaryotes are effective osmotrophs, and the advantage of taller eukaryotic osmotrophs in this deep-water community context has not been addressed. We reconstructed flow-velocity profiles and vertical mixing using canopy flow models appropriate to the densities of the observed communities. Further modeling of processes at organismal surfaces documents increasing uptake with height in the community as a function of thinning of the diffusive boundary layer with increased velocity. The velocity profile, produced by canopy flow in the community, generates this advantage of upward growth. Alternative models of upward growth advantage based on redox/resource gradients fail, given the efficiency of vertical mixing. In benthic communities of osmotrophs of sufficient density, access to flow in low-flow settings provides an advantage to taller architecture, providing a selectional driver for communities of tall eukaryotes in contexts where phototropism cannot contribute to upward growth. These Ediacaran deep-sea fossils were preserved during the increasing oxygenation prior to the Cambrian radiation of animals and likely represent an important phase in the ecological and evolutionary transition to more complex eukaryotic forms.
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Affiliation(s)
- Marco Ghisalberti
- School of Civil, Environmental and Mining Engineering, University of Western Australia, Crawley, WA 6009, Australia
| | - David A Gold
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Matthew E Clapham
- Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Guy M Narbonne
- Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Roger E Summons
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - David T Johnston
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA
| | - David K Jacobs
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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24
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Helliwell KE, Wheeler GL, Smith AG. Widespread decay of vitamin-related pathways: coincidence or consequence? Trends Genet 2013; 29:469-78. [DOI: 10.1016/j.tig.2013.03.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 03/09/2013] [Accepted: 03/25/2013] [Indexed: 02/03/2023]
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25
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Solari CA, Kessler JO, Goldstein RE. A general allometric and life-history model for cellular differentiation in the transition to multicellularity. Am Nat 2013; 181:369-80. [PMID: 23448886 DOI: 10.1086/669151] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The transition from unicellular, to colonial, to larger multicellular organisms has benefits, costs, and requirements. Here we present a model inspired by the volvocine green algae that explains the dynamics involved in the unicellular-multicellular transition using life-history theory and allometry. We model the two fitness components (fecundity and viability) and compare the fitness of hypothetical colonies of different sizes with varying degrees of cellular differentiation to understand the general principles that underlie the evolution of multicellularity. We argue that germ-soma separation may have evolved to counteract the increasing costs and requirements of larger multicellular colonies. The model shows that the cost of investing in soma decreases with size. For lineages such as the Volvocales, as reproduction costs increase with size for undifferentiated colonies, soma specialization benefits the colony indirectly by decreasing such costs and directly by helping reproductive cells acquire resources for their metabolic needs. Germ specialization is favored once soma evolves and takes care of vegetative functions. To illustrate the model, we use some allometric relationships measured in Volvocales. Our analysis shows that the cost of reproducing an increasingly larger group has likely played an important role in the transition to multicellularity and cellular differentiation.
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Affiliation(s)
- Cristian A Solari
- Consejo Nacional de Investigaciones Científicas y Técnicas Researcher, Laboratorio de Biología Comparada de Protistas, Departamento de Biodiversidad y Biología Experimental (Facultad de Ciencias Exactas y Naturales), Universidad de Buenos Aires, Buenos Aires, Argentina C1428EHA.
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26
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Abstract
This review covers essentially all aspects of the organisms in the green algal family Volvocaceae and suggests the genetic history of the various steps in their evolution from their unicellular ancestors.
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Affiliation(s)
- A W Coleman
- Department of Molecular and Cell Biology, Brown University, Providence, Rhode Island 02912, USA
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27
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Nedelcu AM. The evolution of self during the transition to multicellularity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 738:14-30. [PMID: 22399371 DOI: 10.1007/978-1-4614-1680-7_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The notion of ' self' is intrinsically linked to the concepts of identity and individuality. During evolutionary transitions in individuality-such as, for instance, during the origin of the first cell, the origin of the eukaryotic cell and the origin of multicellular individuals-new kinds of individuals emerged from the interaction of previously independent entities. The question discussed here is: How can new types of individuals with qualities that cannot be reduced to the properties of their parts be created at a higher level? This question is addressed in the context of the transition to multicellularity and using the volvocine green algae-a group of closely related unicellular and multicellular species with various degrees of physiological and reproductive unity-as a model system. In this chapter, we review our framework to addressing the evolution of individuality during the transition to multicellularity, focusing on the reorganization of general life-traits and cellular processes and the cooption of environmentally-induced responses.
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Affiliation(s)
- Aurora M Nedelcu
- Biology Department, University of New Brunswick, Fredericton, New Brunswick, Canada.
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28
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High-speed microscopic imaging of flagella motility and swimming in Giardia lamblia trophozoites. Proc Natl Acad Sci U S A 2011; 108:E550-8. [PMID: 21808023 DOI: 10.1073/pnas.1106904108] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report, in this paper, several findings about the swimming and attachment mechanisms of Giardia lamblia trophozoites. These data were collected using a combination of a high-contrast CytoViva imaging system and a particle image velocimetry camera, which can capture images at speeds greater than 800 frames/s. Using this system, we discovered that, during rapid swimming of Giardia trophozoites, undulations of the caudal region contributed to forward propulsion combined with the beating of the flagella pairs. It was also discovered, in contrast to previous studies with 10 times slower image sampling technique, that the anterior and posterolateral flagella beat with a clearly defined power stroke and not symmetrical undulations. During the transition from free swimming to attachment, trophozoites modified their swimming behavior from a rapid rotating motion to a more stable planar swimming. While using this planar swimming motion, the trophozoites used the flagella for propulsion and directional control. In addition to examination of the posterolateral and anterior flagella, a model to describe the motion of the ventral flagella was derived, indicating that the ventral flagella beat in an expanding sine wave. In addition, the structure of the ventrocaudal groove creates boundary conditions that determine the form of beating of the ventral flagella. The results from this study indicate that Giardia is able to simultaneously generate both ciliary beating and typical eukaryotic flagellar beating using different pairs of flagella.
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29
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Solari CA, Drescher K, Goldstein RE. THE FLAGELLAR PHOTORESPONSE IN VOLVOX SPECIES (VOLVOCACEAE, CHLOROPHYCEAE) 1. JOURNAL OF PHYCOLOGY 2011; 47:580-583. [PMID: 27021987 DOI: 10.1111/j.1529-8817.2011.00983.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Steering their swimming direction toward the light is crucial for the viability of Volvox colonies, the larger members of the volvocine algae. While it is known that this phototactic steering is achieved by a difference in behavior of the flagella on the illuminated and shaded sides, conflicting reports suggest that this asymmetry arises either from a change in beating direction or a change in beating frequency. Here, we report direct observations of the flagellar behavior of various Volvox species with different phyletic origin in response to light intensity changes and thereby resolve this controversy: Volvox barberi W. Shaw from the section Volvox sensu Nozaki (2003) changes the direction of the flagellar beating plane, while species encompassed in the group Eudorina (Volvox carteri F. Stein, Volvox aureus Ehrenb., and Volvox tertius Art. Mey.) decrease the flagellar beating frequency, sometimes down to flagellar arrest.
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Affiliation(s)
- Cristian A Solari
- CONICET, Departamento de Biodiversidad y Biología Experimental (FCEyN), Laboratorio de Biología Comparada de Protistas, Universidad de Buenos Aires, Buenos Aires C1428EHA, ArgentinaDepartment of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK
| | - Knut Drescher
- CONICET, Departamento de Biodiversidad y Biología Experimental (FCEyN), Laboratorio de Biología Comparada de Protistas, Universidad de Buenos Aires, Buenos Aires C1428EHA, ArgentinaDepartment of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK
| | - Raymond E Goldstein
- CONICET, Departamento de Biodiversidad y Biología Experimental (FCEyN), Laboratorio de Biología Comparada de Protistas, Universidad de Buenos Aires, Buenos Aires C1428EHA, ArgentinaDepartment of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK
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Rossetti V, Filippini M, Svercel M, Barbour AD, Bagheri HC. Emergent multicellular life cycles in filamentous bacteria owing to density-dependent population dynamics. J R Soc Interface 2011; 8:1772-84. [PMID: 21593029 PMCID: PMC3203479 DOI: 10.1098/rsif.2011.0102] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Filamentous bacteria are the oldest and simplest known multicellular life forms. By using computer simulations and experiments that address cell division in a filamentous context, we investigate some of the ecological factors that can lead to the emergence of a multicellular life cycle in filamentous life forms. The model predicts that if cell division and death rates are dependent on the density of cells in a population, a predictable cycle between short and long filament lengths is produced. During exponential growth, there will be a predominance of multicellular filaments, while at carrying capacity, the population converges to a predominance of short filaments and single cells. Model predictions are experimentally tested and confirmed in cultures of heterotrophic and phototrophic bacterial species. Furthermore, by developing a formulation of generation time in bacterial populations, it is shown that changes in generation time can alter length distributions. The theory predicts that given the same population growth curve and fitness, species with longer generation times have longer filaments during comparable population growth phases. Characterization of the environmental dependence of morphological properties such as length, and the number of cells per filament, helps in understanding the pre-existing conditions for the evolution of developmental cycles in simple multicellular organisms. Moreover, the theoretical prediction that strains with the same fitness can exhibit different lengths at comparable growth phases has important implications. It demonstrates that differences in fitness attributed to morphology are not the sole explanation for the evolution of life cycles dominated by multicellularity.
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Affiliation(s)
- Valentina Rossetti
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Switzerland
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31
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Wu D, Freund JB, Fraser SE, Vermot J. Mechanistic basis of otolith formation during teleost inner ear development. Dev Cell 2011; 20:271-8. [PMID: 21316594 DOI: 10.1016/j.devcel.2010.12.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 10/13/2010] [Accepted: 11/27/2010] [Indexed: 11/26/2022]
Abstract
Otoliths, which are connected to stereociliary bundles in the inner ear, serve as inertial sensors for balance. In teleostei, otolith development is critically dependent on flow forces generated by beating cilia; however, the mechanism by which flow controls otolith formation remains unclear. Here, we have developed a noninvasive flow probe using optical tweezers and a viscous flow model in order to demonstrate how the observed hydrodynamics influence otolith assembly. We show that rotational flow stirs and suppresses precursor agglomeration in the core of the cilia-driven vortex. The velocity field correlates with the shape of the otolith and we provide evidence that hydrodynamics is actively involved in controlling otolith morphogenesis. An implication of this hydrodynamic effect is that otolith self-assembly is mediated by the balance between Brownian motion and cilia-driven flow. More generally, this flow feature highlights an alternative biological strategy for controlling particle localization in solution.
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Affiliation(s)
- David Wu
- Biological Imaging Center, Beckman Institute, Option in Bioengineering, Caltech, Pasadena, CA 91125, USA
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32
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Solari CA, Drescher K, Ganguly S, Kessler JO, Michod RE, Goldstein RE. Flagellar phenotypic plasticity in volvocalean algae correlates with Péclet number. J R Soc Interface 2011; 8:1409-17. [PMID: 21367778 DOI: 10.1098/rsif.2011.0023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Flagella-generated fluid stirring has been suggested to enhance nutrient uptake for sufficiently large micro-organisms, and to have played a role in evolutionary transitions to multicellularity. A corollary to this predicted size-dependent benefit is a propensity for phenotypic plasticity in the flow-generating mechanism to appear in large species under nutrient deprivation. We examined four species of volvocalean algae whose radii and flow speeds differ greatly, with Péclet numbers (Pe) separated by several orders of magnitude. Populations of unicellular Chlamydomonas reinhardtii and one- to eight-celled Gonium pectorale (Pe ∼ 0.1-1) and multicellular Volvox carteri and Volvox barberi (Pe ∼ 100) were grown in diluted and undiluted media. For C. reinhardtii and G. pectorale, decreasing the nutrient concentration resulted in smaller cells, but had no effect on flagellar length and propulsion force. In contrast, these conditions induced Volvox colonies to grow larger and increase their flagellar length, separating the somatic cells further. Detailed studies on V. carteri found that the opposing effects of increasing beating force and flagellar spacing balance, so the fluid speed across the colony surface remains unchanged between nutrient conditions. These results lend further support to the hypothesized link between the Péclet number, nutrient uptake and the evolution of biological complexity in the Volvocales.
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Affiliation(s)
- Cristian A Solari
- CONICET, Laboratorio de Biología Comparada de Protistas, Departamento de Biodiversidad y Biología Experimental (FCEN), Universidad de Buenos Aires, C1428EHA Buenos Aires, Argentina
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Hallmann A. Evolution of reproductive development in the volvocine algae. ACTA ACUST UNITED AC 2010; 24:97-112. [PMID: 21174128 PMCID: PMC3098969 DOI: 10.1007/s00497-010-0158-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 11/27/2010] [Indexed: 11/26/2022]
Abstract
The evolution of multicellularity, the separation of germline cells from sterile somatic cells, and the generation of a male-female dichotomy are certainly among the greatest innovations of eukaryotes. Remarkably, phylogenetic analysis suggests that the shift from simple to complex, differentiated multicellularity was not a unique progression in the evolution of life, but in fact a quite frequent event. The spheroidal green alga Volvox and its close relatives, the volvocine algae, span the full range of organizational complexity, from unicellular and colonial genera to multicellular genera with a full germ-soma division of labor and male-female dichotomy; thus, these algae are ideal model organisms for addressing fundamental issues related to the transition to multicellularity and for discovering universal rules that characterize this transition. Of all living species, Volvox carteri represents the simplest version of an immortal germline producing specialized somatic cells. This cellular specialization involved the emergence of mortality and the production of the first dead ancestors in the evolution of this lineage. Volvocine algae therefore exemplify the evolution of cellular cooperation from cellular autonomy. They also serve as a prime example of the evolution of complex traits by a few successive, small steps. Thus, we learn from volvocine algae that the evolutionary transition to complex, multicellular life is probably much easier to achieve than is commonly believed.
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Affiliation(s)
- Armin Hallmann
- Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany.
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35
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Rushkin I, Kantsler V, Goldstein RE. Fluid velocity fluctuations in a suspension of swimming protists. PHYSICAL REVIEW LETTERS 2010; 105:188101. [PMID: 21231140 DOI: 10.1103/physrevlett.105.188101] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Indexed: 05/30/2023]
Abstract
In dilute suspensions of swimming microorganisms the local fluid velocity is a random superposition of the flow fields set up by the individual organisms, which in turn have multipole contributions decaying as inverse powers of distance from the organism. Here we show that the conditions under which the central limit theorem guarantees a Gaussian probability distribution function of velocities are satisfied when the leading force singularity is a Stokeslet, but are not when it is any higher multipole. These results are confirmed by numerical studies and by experiments on suspensions of the alga Volvox carteri, which show that deviations from Gaussianity arise from near-field effects.
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Affiliation(s)
- Ilia Rushkin
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Raod, Cambridge CB3 0WA, United Kingdom
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Biomimetic cilia arrays generate simultaneous pumping and mixing regimes. Proc Natl Acad Sci U S A 2010; 107:15670-5. [PMID: 20798342 DOI: 10.1073/pnas.1005127107] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Living systems employ cilia to control and to sense the flow of fluids for many purposes, such as pumping, locomotion, feeding, and tissue morphogenesis. Beyond their use in biology, functional arrays of artificial cilia have been envisaged as a potential biomimetic strategy for inducing fluid flow and mixing in lab-on-a-chip devices. Here we report on fluid transport produced by magnetically actuated arrays of biomimetic cilia whose size approaches that of their biological counterparts, a scale at which advection and diffusion compete to determine mass transport. Our biomimetic cilia recreate the beat shape of embryonic nodal cilia, simultaneously generating two sharply segregated regimes of fluid flow: Above the cilia tips their motion causes directed, long-range fluid transport, whereas below the tips we show that the cilia beat generates an enhanced diffusivity capable of producing increased mixing rates. These two distinct types of flow occur simultaneously and are separated in space by less than 5 microm, approximately 20% of the biomimetic cilium length. While this suggests that our system may have applications as a versatile microfluidics device, we also focus on the biological implications of our findings. Our statistical analysis of particle transport identifying an enhanced diffusion regime provides novel evidence for the existence of mixing in ciliated systems, and we demonstrate that the directed transport regime is Poiseuille-Couette flow, the first analytical model consistent with biological measurements of fluid flow in the embryonic node.
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Ueki N, Matsunaga S, Inouye I, Hallmann A. How 5000 independent rowers coordinate their strokes in order to row into the sunlight: phototaxis in the multicellular green alga Volvox. BMC Biol 2010; 8:103. [PMID: 20663212 PMCID: PMC2920248 DOI: 10.1186/1741-7007-8-103] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 07/27/2010] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND The evolution of multicellular motile organisms from unicellular ancestors required the utilization of previously evolved tactic behavior in a multicellular context. Volvocine green algae are uniquely suited for studying tactic responses during the transition to multicellularity because they range in complexity from unicellular to multicellular genera. Phototactic responses are essential for these flagellates because they need to orientate themselves to receive sufficient light for photosynthesis, but how does a multicellular organism accomplish phototaxis without any known direct communication among cells? Several aspects of the photoresponse have previously been analyzed in volvocine algae, particularly in the unicellular alga Chlamydomonas. RESULTS In this study, the phototactic behavior in the spheroidal, multicellular volvocine green alga Volvox rousseletii (Volvocales, Chlorophyta) was analyzed. In response to light stimuli, not only did the flagella waveform and beat frequency change, but the effective stroke was reversed. Moreover, there was a photoresponse gradient from the anterior to the posterior pole of the spheroid, and only cells of the anterior hemisphere showed an effective response. The latter caused a reverse of the fluid flow that was confined to the anterior hemisphere. The responsiveness to light is consistent with an anterior-to-posterior size gradient of eyespots. At the posterior pole, the eyespots are tiny or absent, making the corresponding cells appear to be blind. Pulsed light stimulation of an immobilized spheroid was used to simulate the light fluctuation experienced by a rotating spheroid during phototaxis. The results demonstrated that in free-swimming spheroids, only those cells of the anterior hemisphere that face toward the light source reverse the beating direction in the presence of illumination; this behavior results in phototactic turning. Moreover, positive phototaxis is facilitated by gravitational forces. Under our conditions, V. rousseletii spheroids showed no negative phototaxis. CONCLUSIONS On the basis of our results, we developed a mechanistic model that predicts the phototactic behavior in V. rousseletii. The model involves photoresponses, periodically changing light conditions, morphological polarity, rotation of the spheroid, two modes of flagellar beating, and the impact of gravity. Our results also indicate how recently evolved multicellular organisms adapted the phototactic capabilities of their unicellular ancestors to multicellular life.
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Affiliation(s)
- Noriko Ueki
- Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany
- Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577 Japan
| | - Shigeru Matsunaga
- Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577 Japan
- The Promotion Center for Research and Education, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, 240-0193 Japan
| | - Isao Inouye
- Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8577 Japan
| | - Armin Hallmann
- Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany
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Abstract
Along the evolutionary path from single cells to multicellular organisms with a central nervous system are species of intermediate complexity that move in ways suggesting high-level coordination, yet have none. Instead, organisms of this type possess many autonomous cells endowed with programs that have evolved to achieve concerted responses to environmental stimuli. Here experiment and theory are used to develop a quantitative understanding of how cells of such organisms coordinate to achieve phototaxis, by using the colonial alga Volvox carteri as a model. It is shown that the surface somatic cells act as individuals but are orchestrated by their relative position in the spherical extracellular matrix and their common photoresponse function to achieve colony-level coordination. Analysis of models that range from the minimal to the biologically faithful shows that, because the flagellar beating displays an adaptive down-regulation in response to light, the colony needs to spin around its swimming direction and that the response kinetics and natural spinning frequency of the colony appear to be mutually tuned to give the maximum photoresponse. These models further predict that the phototactic ability decreases dramatically when the colony does not spin at its natural frequency, a result confirmed by phototaxis assays in which colony rotation was slowed by increasing the fluid viscosity.
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Valeriani C, Allen RJ, Marenduzzo D. Non-equilibrium dynamics of an active colloidal “chucker”. J Chem Phys 2010; 132:204904. [DOI: 10.1063/1.3428663] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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40
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Guérin T, Prost J, Martin P, Joanny JF. Coordination and collective properties of molecular motors: theory. Curr Opin Cell Biol 2010; 22:14-20. [PMID: 20074926 DOI: 10.1016/j.ceb.2009.12.012] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 11/25/2009] [Accepted: 12/15/2009] [Indexed: 10/20/2022]
Abstract
Many cellular processes require molecular motors to produce motion and forces. Single molecule experiments have led to a precise description of how a motor works. Under most physiological conditions, however, molecular motors operate in groups. Interactions between motors yield collective behaviors that cannot be explained only from single molecule properties. The aim of this paper is to review the various theoretical descriptions that explain the emergence of collective effects in molecular motor assemblies. These include bidirectional motion, hysteretic behavior, spontaneous oscillations, and self-organization into dynamical structures. We discuss motors acting on the cytoskeleton both in a prescribed geometry such as in muscles or flagella and in the cytoplasm.
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Affiliation(s)
- Thomas Guérin
- Laboratoire Physico-Chimie Curie, CNRS, Institut Curie, UPMC, 26 rue d'Ulm, F-75248 Paris Cedex 05, France
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Polin M, Tuval I, Drescher K, Gollub JP, Goldstein RE. Chlamydomonas swims with two "gears" in a eukaryotic version of run-and-tumble locomotion. Science 2009; 325:487-90. [PMID: 19628868 DOI: 10.1126/science.1172667] [Citation(s) in RCA: 230] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The coordination of eukaryotic flagella is essential for many of the most basic processes of life (motility, sensing, and development), yet its emergence and regulation and its connection to locomotion are poorly understood. Previous studies show that the unicellular alga Chlamydomonas, widely regarded as an ideal system in which to study flagellar biology, swims forward by the synchronous action of its two flagella. Using high-speed imaging over long intervals, we found a richer behavior: A cell swimming in the dark stochastically switches between synchronous and asynchronous flagellar beating. Three-dimensional tracking shows that these regimes lead, respectively, to nearly straight swimming and to abrupt large reorientations, which yield a eukaryotic version of the "run-and-tumble" motion of peritrichously flagellated bacteria.
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Affiliation(s)
- Marco Polin
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
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42
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Drescher K, Leptos KC, Tuval I, Ishikawa T, Pedley TJ, Goldstein RE. Dancing volvox: hydrodynamic bound states of swimming algae. PHYSICAL REVIEW LETTERS 2009; 102:168101. [PMID: 19518757 PMCID: PMC4833199 DOI: 10.1103/physrevlett.102.168101] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Indexed: 05/19/2023]
Abstract
The spherical alga Volvox swims by means of flagella on thousands of surface somatic cells. This geometry and its large size make it a model organism for studying the fluid dynamics of multicellularity. Remarkably, when two nearby Volvox colonies swim close to a solid surface, they attract one another and can form stable bound states in which they "waltz" or "minuet" around each other. A surface-mediated hydrodynamic attraction combined with lubrication forces between spinning, bottom-heavy Volvox explains the formation, stability, and dynamics of the bound states. These phenomena are suggested to underlie observed clustering of Volvox at surfaces.
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Affiliation(s)
- Knut Drescher
- Department of Applied Mathematics, University of Cambridge, Cambridge CB3 0WA, United Kingdom
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Beardall J, Allen D, Bragg J, Finkel ZV, Flynn KJ, Quigg A, Rees TAV, Richardson A, Raven JA. Allometry and stoichiometry of unicellular, colonial and multicellular phytoplankton. THE NEW PHYTOLOGIST 2009; 181:295-309. [PMID: 19121029 DOI: 10.1111/j.1469-8137.2008.02660.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Phytoplankton life forms, including unicells, colonies, pseudocolonies, and multicellular organisms, span a huge size range. The smallest unicells are less than 1 microm3 (e.g. cyanobacteria), while large unicellular diatoms may attain 10(9) microm3, being visible to the naked eye. Phytoplankton includes chemo-organotrophic unicells, colonies and multicellular organisms that depend on symbionts or kleptoplastids for their capacity to photosynthesize. Analyses of physical (transport within cells, diffusion boundary layers, package effect, turgor, and vertical movements) and biotic (grazing, viruses and other parasitoids) factors indicate potential ecological constraints and opportunities that differ among the life forms. There are also variations among life forms in elemental stoichiometry and in allometric relations between biovolume and specific growth. While many of these factors probably have ecological and evolutionary significance, work is needed to establish those that are most important, warranting explicit description in models. Other factors setting limitations on growth rate (selecting slow-growing species) await elucidation.
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Affiliation(s)
- John Beardall
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Drew Allen
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Jason Bragg
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Zoe V Finkel
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Kevin J Flynn
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Antonietta Quigg
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - T Alwyn V Rees
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Anthony Richardson
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - John A Raven
- School of Biological Sciences, PO Box 18, Monash University, Clayton, Vic 3800, Australia;National Center for Ecological Analysis and Synthesis, 735 State St, Suite 300, Santa Barbara, CA 93101, USA;Civil and Environmental Engineering, MIT 48-208, 18 Vassar St, Cambridge, MA 02139, USA;Environmental Science Program, Mount Allison University, Avard-Dixon, 144 Main Street, Sackville, Canada E4L 1A7;Institute of Environmental Sustainability, Wallace Building, University of Swansea, Swansea SA2 8PP, UK;Department of Oceanography, Texas A&M University, 5007 Avenue U, TX 77551, USA;Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth, New Zealand;Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, Qld 4163, Australia;University of Queensland, School of Physical Sciences, St Lucia, Qld 4072, Australia;Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
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44
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Drescher K, Leptos KC, Goldstein RE. How to track protists in three dimensions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2009; 80:014301. [PMID: 19191449 DOI: 10.1063/1.3053242] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We present an apparatus optimized for tracking swimming micro-organisms in the size range of 10-1000 microm, in three dimensions (3Ds), far from surfaces, and with negligible background convective fluid motion. Charge coupled device cameras attached to two long working distance microscopes synchronously image the sample from two perpendicular directions, with narrow band dark-field or bright-field illumination chosen to avoid triggering a phototactic response. The images from the two cameras can be combined to yield 3D tracks of the organism. Using additional, highly directional broad-spectrum illumination with millisecond timing control the phototactic trajectories in 3D of organisms ranging from Chlamydomonas to Volvox can be studied in detail. Surface-mediated hydrodynamic interactions can also be investigated without convective interference. Minimal modifications to the apparatus allow for studies of chemotaxis and other taxes.
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Affiliation(s)
- Knut Drescher
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
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45
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Benoit MR, Brown RB, Todd P, Nelson ES, Klaus DM. Buoyant plumes from solute gradients generated by non-motile Escherichia coli. Phys Biol 2008; 5:046007. [PMID: 19075355 DOI: 10.1088/1478-3975/5/4/046007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The effect of hydrodynamic mixing in bacterial populations due to bacterial chemotaxis is a well-described phenomenon known as bioconvection. Here we report the observation of buoyant plumes that result in hydrodynamic mixing, but in contrast to bioconvection the plumes form in the absence of bacterial motility. We propose that the buoyant flow originates from solute gradients created by bacterial metabolism, similar to solute-induced buoyant flow around growing protein crystals. In our experiments, metabolically-active non-motile Escherichia coli were layered along the bottom of flat-bottomed containers. The E. coli consumed glucose in the medium creating a lighter fluid beneath a heavier fluid. The situation is an example of Rayleigh-Taylor instability, in which a lighter fluid pushes on a heavier one. We developed a numerical model to study the effect of E. coli nutrient consumption and by-product excretion on extracellular solute gradients. The model solutions showed reduced-density fluid along the bottom of the fluid domain leading to buoyant plumes, which were qualitatively similar to the experimental plumes. We also used scaling analyses to study the dependence of plume formation on container size and cell size, and to investigate the effect of reduced gravity, such as the microgravity conditions encountered during spaceflight.
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Affiliation(s)
- M R Benoit
- BioServe Space Technologies, Aerospace Engineering Sciences Department, University of Colorado, USA
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46
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Solari CA, Michod RE, Goldstein RE. VOLVOX BARBERI, THE FASTEST SWIMMER OF THE VOLVOCALES (CHLOROPHYCEAE)(1). JOURNAL OF PHYCOLOGY 2008; 44:1395-1398. [PMID: 27039854 DOI: 10.1111/j.1529-8817.2008.00603.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Volvox barberi W. Shaw is a volvocalean green alga composed of biflagellated cells. Vovocales with 16 cells or more form spherical colonies, and their largest members have germ-soma separation (all species in the genus Volvox). V. barberi is the largest Volvox species recorded in terms of cell number (10,000-50,000 cells) and has the highest somatic to reproductive cell ratio (S/R). Since they are negatively buoyant, Volvocales need flagellar beating to avoid sinking and to reach light and nutrients. We measured V. barberi swimming speed and total swimming force. V. barberi swimming speeds are the highest recorded so far for volvocine algae (∼600 μm · s(-1) ). With this speed, V. barberi colonies have the potential to perform daily vertical migrations in the water column at speeds of 2-3 m · h(-1) , consistent with what has been reported about Volvox populations in the wild. Moreover, V. barberi data fit well in the scaling relationships derived with the other smaller Volvox species, namely, that the upward swimming speed Vup ∝N(0.28) and the total swimming force FS ∝N(0.77) (N = colony cell number). These allometric relationships have been important supporting evidence for reaching the conclusion that as size increases, colonies have to invest in cell specialization and increase their S/R to increase their motility capabilities to stay afloat and motile.
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Affiliation(s)
- Cristian A Solari
- CONICET Researcher, Laboratorio de Biología Comparada de Protistas, Departamento de Biodiversidad y Biología Experimental (FCEyN), Universidad de Buenos Aires, Buenos Aires, Argentina C1428EHADepartment of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USADepartment of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, UK
| | - Richard E Michod
- CONICET Researcher, Laboratorio de Biología Comparada de Protistas, Departamento de Biodiversidad y Biología Experimental (FCEyN), Universidad de Buenos Aires, Buenos Aires, Argentina C1428EHADepartment of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USADepartment of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, UK
| | - Raymond E Goldstein
- CONICET Researcher, Laboratorio de Biología Comparada de Protistas, Departamento de Biodiversidad y Biología Experimental (FCEyN), Universidad de Buenos Aires, Buenos Aires, Argentina C1428EHADepartment of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USADepartment of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, UK
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47
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Abstract
Most conspicuous organisms are multicellular and most multicellular organisms develop somatic cells to perform specific, nonreproductive tasks. The ubiquity of this division of labor suggests that it is highly advantageous. In this article I present a model to study the evolution of specialized cells. The model allows for unicellular and multicellular organisms that may contain somatic (terminally differentiated) cells. Cells contribute additively to a quantitative trait. The fitness of the organism depends on this quantitative trait (via a benefit function), the size of the organism, and the number of somatic cells. The model allows one to determine when somatic cells are advantageous and to calculate the optimum number (or fraction) of reproductive cells. I show that the fraction of reproductive cells is always surprisingly high. If somatic cells are very small, they can outnumber reproductive cells but their biomass is still less than the biomass of reproductive cells. I discuss the biology of primitive multicellular organisms with respect to the model predictions. I find a good agreement and outline how this work can be used to guide further quantitative studies of multicellularity.
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Affiliation(s)
- Martin Willensdorfer
- Program for Evolutionary Dynamics, Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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48
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Yip EC, Powers KS, Avilés L. Cooperative capture of large prey solves scaling challenge faced by spider societies. Proc Natl Acad Sci U S A 2008; 105:11818-22. [PMID: 18689677 PMCID: PMC2575263 DOI: 10.1073/pnas.0710603105] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Indexed: 11/18/2022] Open
Abstract
A decrease in the surface area per unit volume is a well known constraint setting limits to the size of organisms at both the cellular and whole-organismal levels. Similar constraints may apply to social groups as they grow in size. The communal three-dimensional webs that social spiders build function ecologically as single units that intercept prey through their surface and should thus be subject to this constraint. Accordingly, we show that web prey capture area per spider, and thus number of insects captured per capita, decreases with colony size in a neotropical social spider. Prey biomass intake per capita, however, peaks at intermediate colony sizes because the spiders forage cooperatively and larger colonies capture increasingly large insects. A peaked prey biomass intake function would explain not only why these spiders live in groups and cooperate but also why they disperse only at large colony sizes, thus addressing both sociality and colony size range in this social spider. These findings may also explain the conspicuous absence of social spiders from higher latitudes and higher elevations, areas that we have previously shown to harbor considerably fewer insects of the largest size classes than the lowland tropical rainforests where social spiders thrive. Our findings thus illustrate the relevance of scaling laws to the size and functioning of levels of organization above the individual.
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Affiliation(s)
- Eric C. Yip
- *Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; and
| | - Kimberly S. Powers
- *Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; and
| | - Leticia Avilés
- *Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; and
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Llopis I, Pagonabarraga I. Hydrodynamic regimes of active rotators at fluid interfaces. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2008; 26:103-113. [PMID: 18398566 DOI: 10.1140/epje/i2007-10295-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 02/12/2008] [Indexed: 05/26/2023]
Abstract
We analyze the collective motion of suspensions of active rotators at low Reynolds numbers which interact hydrodynamically. We introduce a simple model for a rotator which allows us to classify the relevant dynamical regimes of the suspension. We characterize the collective velocity at which rotators displace and analyze its implications at long times, when these rotator suspensions diffuse. We analyze the differences with respect to diffusion in suspensions of passive particles, and assess the relevance of the Stokes-Einstein relation on rotators' diffusivity.
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Affiliation(s)
- I Llopis
- Departament de Fisica Fonamental, Universitat de Barcelona, C. Marti i Franqués 1, Barcelona, Spain
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Microfluidics of cytoplasmic streaming and its implications for intracellular transport. Proc Natl Acad Sci U S A 2008; 105:3663-7. [PMID: 18310326 DOI: 10.1073/pnas.0707223105] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Found in many large eukaryotic cells, particularly in plants, cytoplasmic streaming is the circulation of their contents driven by fluid entrainment from particles carried by molecular motors at the cell periphery. In the more than two centuries since its discovery, streaming has frequently been conjectured to aid in transport and mixing of molecular species in the cytoplasm and, by implication, in cellular homeostasis, yet no theoretical analysis has been presented to quantify these processes. We show by a solution to the coupled dynamics of fluid flow and diffusion appropriate to the archetypal "rotational streaming" of algal species such as Chara and Nitella that internal mixing and the transient dynamical response to changing external conditions can indeed be enhanced by streaming, but to an extent that depends strongly on the pitch of the helical flow. The possibility that this may have a developmental consequence is illustrated by the coincidence of the exponential growth phase of Nitella and the point of maximum enhancement of those processes.
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