DOCSLIB.ORG

Phototactic Purple Bacteria Extinction Or Miscalculation?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Phototactic Purple Bacteria Extinction Or Miscalculation? SCIENTIFIC CORRESPONDENCE the light source through the gradient of Phototactic purple decreasing light intensity; on the other Extinction or hand, if their movement is scotophobic, bacteria the colony should move in the opposite miscalculation? direction. R. centenum swarm colonies SIR - In 1883 T. Engelmann! discovered irradiated laterally with infrared light in SIR - Heywood et al. I have discussed that purple photosynthetic bacteria re­ fact moved rapidly towards the light uncertainties in modelling rates. One way verse their swimming direction when the source, as for positive phototaxis. to check a predictive model's validity is to light intensity is suddenly reduced. He Anoxygenic photosynthetic bacteria see how well it predicts past events. In this described this photosensory effect as and the oxygenic cyanobacteria and algae case, the species-area relation model does "Schreckbewegung" ('movement of share several similar physiological re­ fairly well in predicting the number of fright'), but it is more properly designated quirements, so it is not surprising that bird and mammal extinctions during the as a scotophobic response, past 500 years in the United States and that is, a fear of darkness. a Canada .. Scotophobic behaviour is Time (min) Infrared Here I consider species extirpated fol­ typical of motile purple bac­ lowing habitat destruction initiated by 2 teria, is independent of the o Europeans in North America , combined direction of illumination, with currently endangered or threatened 3 and does not occur if the 30 species , to check if species loss is con­ light intensity is reduced ..'Q" gruent with habitat loss. Although exact only gradually. By contrast, 60 figures are difficult to come by, I take as oxygenic cyanobacteria and 20% the amount of land removed from algae exhibit phototactic re- 120 native North American mammal and bird 4 sponses, that is, oriented habitats . Applying the species-area rela­ movement towards or away tion, So=kA z, gives the number of species from a light source, b originally present, and Sl=k(0.8AY irrespective of its intensity. Time (min) Visible gives the number remaining today (for We show here that the non­ non-isolates 0.12 :::; z :::; 0.17; for true sulphur purple bacterium o island isolates z = 0.25; ref. 5). Thus Rhodospirillum centenum2 1-(S/So)=1-(0.8Y is the fraction of can also move with respect 30 original species lost. to the direction of illumina- ..'Q"- The values of z usually observed for tion and that this photo­ 60 non-isolates indicate species loss is in the tactic behaviour is observ­ range 2.65-3.72%. The number of terrest­ able macroscopically. rial bird species threatened, endangered 120 When grown photo­ or extinct in North America is 18. The trophically in a liquid question is, then, does 18 correspond to medium, R. centenum cells 2.65-3.72% of the original bird fauna? bear a single polar Phototactic behaviour of R. centenum swarm colonies by Working backwards to deduce T, the total flagellum, but when grown time-lapse photography. a. An R. centenum swarm colony number of bird species originally present, exposed to 575 flW of infrared light of wavelength above 650 aerobically in darkness on gives 679 :::; T:::; 484, which does bound nm; b, swarm colony exposed to 2.500 flW of visible light of 0.8% agar containing 0.3% wavelength below 650 nm. Scale bar, 10 mm. the roughly 600 known breeding species in peptone they produce many North America, plus extinctions. peritrichous flagella. Such cells contain representatives of these three groups I used the non-isolate z because birds the normal complement of photosynthetic of phototrophs are phototactic. Photo­ are good dispersers and 'habitat islands' pigments3 and form phototactic 'swarm taxis is believed to help motile photo­ are less likely to be truly isolated for birds colonies'; the figure shows that lateral synthetic organisms move towards zones than for mammals. For mammals, which illumination of such a colony with infrared where conditions are better for growth; do not disperse as readily as birds, I chose light causes positive phototaxis (a) or for example, it is well known that cyano­ an isolate value for z of 0.25 (ref. 5). negative phototaxis with visible light (b). bacteria and anoxygenic photosynthetic This indicates a species loss of 5.4% for Action spectra and details of the re­ bacteria accumulate in discrete bands mammals. Using 19, the number of sponses of swarm colonies to simul­ in stratified lakes and laminated micro­ terrestrial mammal species threatened, 5 taneous illumination with perpendicular bial mats . endangered or extinct in North America, beams of light will be published elsewhere Lisa Ragatz and again working backwards, the orig­ (manuscript in preparation). Ze-YuJiang inal number of mammal species is around Several ad hoc assumptions would be Carl Bauer 352. This is in reasonable agreement necessary to explain the movement of R. Howard Gest with the roughly 300 extant species plus centenum swarm colonies towards or away Indiana University, extinctions. from light sources on the basis of sco­ Department of Biology, This thumbnail analysis supports the tophobic responses of randomly moving Bloomington, use of species-area curves to predict spe­ cells. Nevertheless, we also tcsted for Indiana 47405, USA cies extinctions due to habitat loss, at least authentic phototaxis using a technique 4 previously applied to phototactic algae . 1. Engelmann. Th. W. Arch. gesam. Physiol. Mensch. u. Thiere30. 95-124 (1883). 1. Heywood, V. H. etal. Nature 368. 105 (1994) Infrared light was passed through a con­ 2. Favinger.J" Stadtwald. R. & Gest. H. Ant. 2. Williams. J. D. & Nowak, R. M. in The Last Extinction (eds verging lens to focus on a swarm colony. v. Leeuwenhoek. J. Microbiol. 55. 291-296 Kaufman. L. &Mallory, K.) 115-148 (MIT, Cambridge. At the edge of the colony, the light (1989). Massachusetts. 1993). 3. Yildiz. F. H .. Gest. H. & Bauer. C. E.J. 8act.173. 3. Endangered and Threatened Wildlife and Plants Code of intensity was relatively high and the in­ 5502-5506 (1991). Federal Regulations 50: 17.11 & 17 .12 (US Dept of tensity gradient decreased in the direction 4. BUder.J.Jb. wiss. 80t. 58.105-220 Interior, Washington DC, 1992). (1917) 4. Ray. D. L. & Guzzo. L. Environmental Overkill (Regnery of the light source. A positive phototactic 5. Madigan, M. T. in Biology ofAnaerobic Microorganisms Gateway. Washington DC. 1993). organism or colony should move towards (ed. Zehnder. A. J. B.) 39-111 (Wiley. New York, 1988). 5. Preston. F. W. Ecology 43. 185 (1962). 104 NATURE· VOL 370 . 14 JULY 1994 .
Load more

Recommended publications
  • Phototaxis and Membrane Potential in the Photosynthetic Bacterium Rhodospirillum Rubrum
    JOURNAL OF BACTEIUOLOGY, July 1977, p. 34-41 Vol. 131, No. 1 Copyright © 1977 American Society for Microbiology Printed in U.S.A. Phototaxis and Membrane Potential in the Photosynthetic Bacterium Rhodospirillum rubrum SHIGEAKI HARAYAMA* AND TETSUO IINO Laboratory of Genetics, Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan Received for publication 23 February 1977 Cells of the photosynthetic bacterium Rhodospirillum rubrum cultivated anaerobically in light show phototaxis. The behavior of individual cells in response to the phenomenon is reversal(s) of the swimming direction when the intensity of the light available to them abruptly decreases. The tactic response was inhibited by antimycin, an inhibitor of the photosynthetic electron transfer system. The inhibitory effect of antimycin was overcome by phenazine metho- sulfate. Motility of the cells was not impaired by antimycin under aerobic conditions. Valinomycin plus potassium also inhibited their phototactic re- sponse; however, valinomycin or potassium alone had no effect. A change in membrane potential of the cells was measured as an absorbance change of carotenoid. Changes in the membrane potential caused by "on-off' light were prevented by antimycin and by valinomycin plus potassium, but not by antimy- cin plus phenazine methosulfate nor valinomycin or potassium alone. The results indicated that the phototactic response of R. rubrum is mediated by a sudden change in electron flow in the photosynthetic electron transfer system, and that the membrane potential plays an important role in manifestation of the re- sponse. Bacterial phototaxis has been observed in systems. The chemotactic behavior of individ- photosynthetic bacteria (6, 22) and in Halobac- ual cells ofE.
    [Show full text]
  • Schmitt-2011-Thalassas.Pdf
    Thalassas, 27 (2): 225-238 An International Journal of Marine Sciences BEHAVIORAL ADAPTATIONS IN RELATION TO LONG-TERM RETENTION OF ENDOSYMBIOTIC CHLOROPLASTS IN THE SEA SLUG Elysia timida (OPISTHOBRANCHIA, SACOGLOSSA) VALÉRIE SCHMITT (1, 2) & HEIKE WÄGELE (1) Key words: Sacoglossa, endosymbiosis, chloroplasts, retention, phototaxis, photobehavior. ABSTRACT in basins with running seawater and natural light through a glass window. Behavioral observations A comparative study was performed to analyze and PAM-measurements were performed in 4 time differences in evolutionary adaptations in two sea intervals in the course of an observation day in slug species, Elysia timida with long-term retention of daylight and dark-adapted conditions. Phototactic endosymbiotic chloroplasts and Thuridilla hopei with behavior was found to be present in both compared short-term retention of endosymbiotic chloroplasts. species, although the phototactic reaction was Both sacoglossan species stem from the same habitat more pronounced in E. timida. Phototaxis was also and show similar body sizes and structures with observed in juvenile E. timida before sequestration parapodial lobes whose position can be actively of first Acetabularia-chloroplasts, which indicates varied by the slugs. Ethological analyses were carried no direct current influence of the endosymbiotic out concerning the positioning of parapodia and chloroplasts. Other parameters, however, like the other photobehavioral parameters like phototaxis. In positioning of the parapodia, were observed to parallel, photosynthetic activity was measured with be significantly different between the long-term a Pulse Amplitude Modulated Fluorometer (PAM). and short-term storing species. While an adapted In total, 252 E. timida individuals and 63 T. hopei changing of the parapodia’s position in reaction to individuals were included in the analysis.
    [Show full text]
  • Ontogeny of Orientation During the Early Life History of the Pelagic Teleost Mahi-Mahi, Coryphaena Hippurus Linnaeus, 1758
    Article Ontogeny of Orientation during the Early Life History of the Pelagic Teleost Mahi-Mahi, Coryphaena hippurus Linnaeus, 1758 Robin Faillettaz 1,2,* , Eve Johnson 1, Patrick Dahlmann 1, Alexandra Syunkova 1, John Stieglitz 3, Daniel Benetti 3, Martin Grosell 1 and Claire B. Paris 1,* 1 Department of Marine Biology and Ecology, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA; [email protected] (E.J.); [email protected] (P.D.); [email protected] (A.S.); [email protected] (M.G.) 2 Ifremer, STH, Station de Lorient, 8 rue François Toullec, F-56100 Lorient, France 3 Department of Marine Ecosystems and Society, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA; [email protected] (J.S.); [email protected] (D.B.) * Correspondence: [email protected] (R.F.); [email protected] (C.B.P.) Received: 6 July 2020; Accepted: 29 September 2020; Published: 8 October 2020 Abstract: Understanding the orientation behavior and capabilities in early life history (ELH) of fishes is critical for studying their dispersal but has, surprisingly, never been tested in any pelagic species. We here investigate the ontogeny of orientation and swimming abilities of the pelagic Coryphaena hippurus Linnaeus, 1758 larvae, hereafter mahi-mahi, through their ELH stages using the Drifting In Situ Chamber (DISC) in a laboratory setup. The DISC was deployed in a large (3 m3) circular aquarium in order to control the stimulus perceived by the fish and to identify behavioral response at the individual, developmental stage, and population levels.
    [Show full text]
  • Planarian Behavior: a Student-Designed Laboratory Exercise
    Planarian Behavior: A Student-Designed Laboratory Exercise Linda T. Collins and Brent W. Harker Department of Biological and Environmental Sciences University of Tennessee at Chattanooga Chattanooga, TN 37403 [email protected] Reprinted From: Collins, L. T. and B. W. Harker. 1999. Planarian behavior: A student-designed laboratory exercise. Pages 375-379, in Tested studies for laboratory teaching, Volume 20 (S. J. Karcher, Editor). Proceedings of the 20th Workshop/Conference of the Association for Biology Laboratory Education (ABLE), 399 pages. - Copyright policy: http://www.zoo.utoronto.ca/able/volumes/copyright.htm Although the laboratory exercises in ABLE proceedings volumes have been tested and due consideration has been given to safety, individuals performing these exercises must assume all responsibility for risk. The Association for Biology Laboratory Education (ABLE) disclaims any liability with regards to safety in connection with the use of the exercises in its proceedings volumes. © Linda T. Collins and Brent W. Harker Objectives 1. Know that different types of stimuli can affect planarian movement. 2. Distinguish between kinesis and taxis. 3. After preliminary observations, state a hypothesis to predict or explain planarian movement in response to an external stimulus. Test the hypothesis and reach a conclusion. Introduction Planarians are in the flatworm phylum, Platyhelminthes. Most planarians are free-living and are common in freshwater habitats. They are also found in marine and terrestrial environments. Planarians display bilateral symmetry, meaning the right and left halves are approximately mirror images of each other. The nervous system of planarians consists of an anterior “brain” consisting of large ganglia. Two ventral nerve cords run the length of the body from the ganglia.
    [Show full text]
  • Characterization of Chlamydomonas Reinhardtii Mutants That Exhibit Strong Positive Phototaxis
    plants Article Characterization of Chlamydomonas reinhardtii Mutants That Exhibit Strong Positive Phototaxis Jun Morishita 1,2, Ryutaro Tokutsu 3,4,†, Jun Minagawa 3,4 , Toru Hisabori 1,2 and Ken-ichi Wakabayashi 1,2,* 1 Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan; [email protected] (J.M.); [email protected] (T.H.) 2 School of Life Science and Technology, Tokyo Institute of Technology, Yokohama 226-8503, Japan 3 Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan; [email protected] (R.T.); [email protected] (J.M.) 4 Department of Basic Biology, Faculty of Life Science, The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan * Correspondence: [email protected] † Current address: Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. Abstract: The most motile phototrophic organisms exhibit photo-induced behavioral responses (photobehavior) to inhabit better light conditions for photosynthesis. The unicellular green alga Chlamydomonas reinhardtii is an excellent model organism to study photobehavior. Several years ago, we found that C. reinhardtii cells reverse their phototactic signs (i.e., positive and negative phototaxis) depending on the amount of reactive oxygen species (ROS) accumulated in the cell. However, its molecular mechanism is unclear. In this study, we isolated seven mutants showing positive Citation: Morishita, J.; Tokutsu, R.; phototaxis, even after the induction of negative phototaxis (ap1~7: always positive) to understand the Minagawa, J.; Hisabori, T.; ROS-dependent regulatory mechanism for the phototactic sign.
    [Show full text]
  • How Chlamydomonas Keeps Track of the Light Once It Has Reached the Right Phototactic Orientation
    1562 Biophysical Journal Volume 73 September 1997 1562-1562 How Chiamydomonas Keeps Track of the Light Once It Has Reached the Right Phototactic Orientation Klaus Schaller, Ruth David, and Rainer Uhl Abteilung Physikalische Biologie der Ludwig Maximilians Universitat, D-80638 Munchen, Germany ABSTRACT By using a real-time assay that allows measurement of the phototactic orientation of the unicellular alga Chlamydomonas with millisecond time resolution, it can be shown that single photons not only induce transient direction changes but that fluence rates as low as 1 photon cell-1 s-1 can already lead to a persistent orientation. Orientation is a binary variable, i.e., in a partially oriented population some organisms are fully oriented while the rest are still at random. Action spectra reveal that the response to a pulsed stimulus follows the Dartnall-nomogram for a rhodopsin while the response to a persistent stimulus falls off more rapidly toward the red end of the spectrum. Thus light of 540 nm, for which ch/amy-rhodopsin is equally sensitive as for 440-nm light, induces no measurable persistent orientation while 440-nm light does. A model is presented which explains not only this behavior, but also how Chlamydomonas can track the light direction and switches between a positive and negative phototaxis. According to the model the ability to detect the direction of light, to make the right turn and to stay oriented, is a direct consequence of the helical path of the organism, the orientation of its eyespot relative to the helix-axis, and the special shielding properties of eyespot and cell body.
    [Show full text]
  • Phototaxis During the Slug Stage of Dictyostelium Discoideum: a Model Study
    Phototaxis during the slug stage of Dictyostelium discoideum: a model study Athanasius F. M. Mare¨ e*, Alexander V. Pan¢lov and Paulien Hogeweg Theoretical Biology and Bioinformatics, University of Utrecht, Padualaan 8, 3584 CH Utrecht,The Netherlands During the slug stage, the cellular slime mould Dictyostelium discoideum moves towards light sources. We have modelled this phototactic behaviour using a hybrid cellular automata/partial di¡erential equation model. In our model, individual amoebae are not able to measure the direction from which the light comes, and di¡erences in light intensity do not lead to di¡erentiation in motion velocity among the amoebae. Nevertheless, the whole slug orientates itself towards the light. This behaviour is mediated by a modi¢cation of the cyclic AMP (cAMP) waves. As an explanation for phototaxis we propose the following mechanism, which is basically characterized by four processes: (i) light is focused on the distal side of the slug as a result of the so-called `lens-e¡ect'; (ii) di¡erences in luminous intensity cause di¡erences in NH3 concentration; (iii) NH3 alters the excitability of the cell, and thereby the shape of the cAMP wave; and (iv) chemotaxis towards cAMP causes the slug to turn. We show that this mechanism can account for a number of other behaviours that have been observed in experiments, such as bidirec- tional phototaxis and the cancellation of bidirectionality by a decrease in the light intensity or the addition of charcoal to the medium. Keywords: Dictyostelium; phototaxis; biological models; movement; ammonia; cyclic AMP slug (Francis 1964), placing the slug in mineral oil 1.
    [Show full text]
  • The Bardet–Biedl Syndrome Protein Complex Is an Adapter Expanding
    The Bardet–Biedl syndrome protein complex is an PNAS PLUS adapter expanding the cargo range of intraflagellar transport trains for ciliary export Peiwei Liua and Karl F. Lechtrecka,1 aDepartment of Cellular Biology, University of Georgia, Athens, GA 30602 Edited by Jennifer Lippincott-Schwartz, Howard Hughes Medical Institute and Janelia Research Campus, Ashburn, VA, and approved December 22, 2017 (received for review July 25, 2017) Bardet–Biedl syndrome (BBS) is a ciliopathy resulting from defects in proteins have been implicated in vesicular traffic to and from the the BBSome, a conserved protein complex. BBSome mutations af- plasma membrane (2, 19–21). Understanding BBSome function fect ciliary membrane composition, impairing cilia-based signaling. could profit from direct monitoring of BBSome-dependent The mechanism by which the BBSome regulates ciliary membrane intracellular transport. content remains unknown. Chlamydomonas bbs mutants lack pho- In Chlamydomonas reinhardtii, mutations in the BBSome impair totaxis and accumulate phospholipase D (PLD) in the ciliary mem- phototaxis and cause biochemical defects of the ciliary membrane brane. Single particle imaging revealed that PLD comigrates with (4, 22). Phospholipase D (PLD) and an AMP-regulated kinase BBS4 by intraflagellar transport (IFT) while IFT of PLD is abolished in (AMPK) (XP_001697837, referred to as STPK in ref. 4) accu- bbs mutants. BBSome deficiency did not alter the rate of PLD entry mulate in bbs cilia while the amount of carbonic anhydrase 6 into cilia. Membrane association and the N-terminal 58 residues of (CAH6) is reduced (5). All three proteins are predicted to be dual PLD are sufficient and necessary for BBSome-dependent transport fatty acid modified at the N terminus.
    [Show full text]
  • Phototaxis Beyond Turning: Persistent Accumulation and Response
    www.nature.com/scientificreports OPEN Phototaxis beyond turning: persistent accumulation and response acclimation of the Received: 29 December 2016 Accepted: 2 May 2017 microalga Chlamydomonas Published: xx xx xxxx reinhardtii Jorge Arrieta1, Ana Barreira1, Maurizio Chioccioli2, Marco Polin3 & Idan Tuval1 Phototaxis is an important reaction to light displayed by a wide range of motile microorganisms. Flagellated eukaryotic microalgae in particular, like the model organism Chlamydomonas reinhardtii, steer either towards or away from light by a rapid and precisely timed modulation of their flagellar activity. Cell steering, however, is only the beginning of a much longer process which ultimately allows cells to determine their light exposure history. This process is not well understood. Here we present a first quantitative study of the long timescale phototactic motility ofChlamydomonas at both single cell and population levels. Our results reveal that the phototactic strategy adopted by these microorganisms leads to an efficient exposure to light, and that the phototactic response is modulated over typical timescales of tens of seconds. The adaptation dynamics for phototaxis and chlorophyll fluorescence show a striking quantitative agreement, suggesting that photosynthesis controls quantitatively how cells navigate a light field. The fitness of microorganisms depends critically on their ability to sense dynamic physico-chemical clues from the environment, elaborate the information and respond effectively. Environmental responses range from changes in gene expression1 (typical timescale ~10 min); to the activation/deactivation of biochemical processes like chloroplast photoprotection2 (~1 min); to fast movement regulation (~1 s), either active3, 4 or passive5. The best characterised motile response is currently chemotaxis of run-and-tumble bacteria like E.
    [Show full text]
  • Regulation of Movement Speed by Intracellular Ph During Dictyostelium Discoideum Chemotaxis (Amoeboid Movement/Random Movement/Camp/Signal Transduction/Ph Change) B
    Proc. Nati. Acad. Sci. USA Vol. 88, pp. 4951-4955, June 1991 Cell Biology Regulation of movement speed by intracellular pH during Dictyostelium discoideum chemotaxis (amoeboid movement/random movement/cAMP/signal transduction/pH change) B. VAN DUUN*t§ AND K. INOUYE* *Department of Botany, Faculty of Science, Kyoto University, Kyoto 606, Japan; tDepartment of Physiology and Physiological Physics, Leiden University, P.O. Box 9604, NL-2300 RC Leiden, The Netherlands; and tCell Biology and Genetics Unit, Zoological Laboratories, Leiden University, Kaiserstraat 63, NL-2311 GP Leiden, The Netherlands Communicated by J. T. Bonner, February 22, 1991 ABSTRACT Evidence is presented that the chemoattrac- aerogenes or Escherichia coli 281 on modified SM medium tant-induced cytoplasmic alklinization in the cellular slime (4.4 g of KH2PO4, 2.0 g of Na2HPO4, 1.0 g of MgSO4-7 H20, mold Dictyostelium discoideum is essential in regulating loco- 7.5 g of glucose, 10.0 g of Bacto-peptone (Difco), 1.0 g of motion speed during chemotaxis. Intracellular pH was manip- yeast extract (Difco), 15 g of agar, 1 liter of H20) at 220C. ulated with weak bases, weak acids, and proton-pump inhibi- Vegetative cells were harvested with cold 20 mM sodium/ tion. Speed of locomotion of individual cells was measured potassium phosphate buffer, pH 6.0 (PB), and washed free of during random and chemotactic movement. We found that (i) bacteria by repeated washes and centrifugation. Starved cells an increase of cytoplasmic pH increases the speed of randomly were obtained by incubating cells on nonnutrient agar (1.5% moving cells and (ii) the chemoattractant-induced rise in agar in H20) at a density of 1.5 x 106 cells per cm2 for -4 hr intracellular pH is essential for the increase in directed loco- at 22°C, after which cells were shaken in suspension in PB for motion speed upon chemotactic stimulation.
    [Show full text]
  • Motility and Phototaxis of Gonium, the Simplest Differentiated
    bioRxiv preprint doi: https://doi.org/10.1101/845891; this version posted November 20, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. Motility and Phototaxis of Gonium, the Simplest Differentiated Colonial Alga H´el`enede Maleprade1, Fr´ed´ericMoisy2, Takuji Ishikawa3, and Raymond E. Goldstein1∗ 1Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom 2Laboratoire FAST, Universit´eParis-Sud, CNRS, Universti´eParis-Saclay - Paris, France 3Department of Finemechanics, Graduate School of Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan (Dated: November 19, 2019) Green algae of the Volvocine lineage, spanning from unicellular Chlamydomonas to vastly larger Volvox, are models for the study of the evolution of multicellularity, flagellar dynamics, and develop- mental processes. Phototactic steering in these organisms occurs without a central nervous system, driven solely by the response of individual cells. All such algae spin about a body-fixed axis as they swim; directional photosensors on each cell thus receive periodic signals when that axis is not aligned with the light. The flagella of Chlamydomonas and Volvox both exhibit an adaptive response to such signals in a manner that allows for accurate phototaxis, but in the former the two flagella have distinct responses, while the thousands of flagella on the surface of spherical Volvox colonies have essentially identical behaviour.
    [Show full text]
  • Chlamydomonas Reinhardtii
    Syracuse University SURFACE Physics - Dissertations College of Arts and Sciences 2011 Bioenergetics and dynamics of ciliary responses and systems biology of phototaxis in Chlamydomonas reinhardtii Suphatra Adulrattananuwat Syracuse University Follow this and additional works at: https://surface.syr.edu/phy_etd Part of the Physics Commons Recommended Citation Adulrattananuwat, Suphatra, "Bioenergetics and dynamics of ciliary responses and systems biology of phototaxis in Chlamydomonas reinhardtii" (2011). Physics - Dissertations. 111. https://surface.syr.edu/phy_etd/111 This Dissertation is brought to you for free and open access by the College of Arts and Sciences at SURFACE. It has been accepted for inclusion in Physics - Dissertations by an authorized administrator of SURFACE. For more information, please contact [email protected]. Abstract The goal of this dissertation is to understand how a eukaryotic cell makes decisions. Chlamydomonas reinhardtii, a biciliated unicellular green alga, is used as our model organism. This organism has the ability to track the light using its photoreceptor called rhodopsin, which overlays the eyespot. The organism makes decisions to swim toward, away from, perpendicular to or to ignore the light using its slender arm-like structures called cilia. It can integrate several external inputs such as ion concentration and light intensity, and then process this information to adjust the steering of its cilia corresponding to its environment. We investigated how red light (670 nm) influences cell behavior. Most studies were done with a single cell held on a micropipette making it possible to observe the cilia behavior over a long time. The cell is illuminated with near-infrared light (peak at 870 nm) to avoid photoreceptor excitation.
    [Show full text]