title: Cyanobacteria use micro-optics to sense light direction.
abstract: Bacterial phototaxis was first recognized over a century ago, but the method by which such small cells can sense the direction of illumination has remained puzzling. The unicellular cyanobacterium Synechocystis sp. PCC 6803 moves with Type IV pili and measures light intensity and color with a range of photoreceptors. Here, we show that individual Synechocystis cells do not respond to a spatiotemporal gradient in light intensity, but rather they directly and accurately sense the position of a light source. We show that directional light sensing is possible because Synechocystis cells act as spherical microlenses, allowing the cell to see a light source and move towards it. A high-resolution image of the light source is focused on the edge of the cell opposite to the source, triggering movement away from the focused spot. Spherical cyanobacteria are probably the world's smallest and oldest example of a camera eye.
authors: Institute of Biology III, University of Freiburg, Freiburg, Germany.
authors: Nils
authors: N
authors: Schuergers
authors: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
authors: Tchern
authors: T
authors: Lenn
authors: Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors: Ronald
authors: R
authors: Kampmann
authors: Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors: Markus V
authors: MV
authors: Meissner
authors: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.|INEB- Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal.|Faculdade de Engenharia da Universidade do Porto, Portugal.
authors: Tiago
authors: T
authors: Esteves
authors: Freiburg Institute for Advanced Studies, University of Freiburg, Freiburg, Germany.
authors: Maja
authors: M
authors: Temerinac-Ott
authors: Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors: Jan G
authors: http://orcid.org/0000-0003-4354-7295
authors: JG
authors: Korvink
authors: London Centre for Nanotechnology, London, United Kingdom.|Institute for Structural and Molecular Biology, University College London and Birkbeck College London, London, United Kingdom.
authors: Alan R
authors: http://orcid.org/0000-0002-0558-3597
authors: AR
authors: Lowe
authors: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.|Freiburg Institute for Advanced Studies, University of Freiburg, Freiburg, Germany.
authors: Conrad W
authors: CW
authors: Mullineaux
authors: Institute of Biology III, University of Freiburg, Freiburg, Germany.|BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany.
authors: Annegret
authors: A
authors: Wilde
mesh_terms: D008027:Light; D008124:Locomotion; D046939:Synechocystis / Q000502:physiology* / Q000528:radiation effects*
keywords: Cyanobacteria; Micro-optics; Phototaxis; Signal transduction; Synechocystis sp PCC6803; Thermosynechococcus elongatus; biophysics; infectious disease; microbiology; structural biology