U-turn time and velocity dependence on the wavelength of light: multicellular magnetotactic prokaryotes of different siz
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ORIGINAL ARTICLE
U‑turn time and velocity dependence on the wavelength of light: multicellular magnetotactic prokaryotes of different sizes behave differently Marcos Venicio Gonçalves Sales1 · Beatriz Silva Lima1 · Daniel Acosta‑Avalos1 Received: 15 May 2020 / Revised: 17 August 2020 / Accepted: 19 October 2020 © European Biophysical Societies’ Association 2020
Abstract ‘Candidatus Magnetoglobus multicellularis’ is a multicellular magnetotactic prokaryote found in the Araruama lagoon in Rio de Janeiro, Brazil. This microorganism shows a photokinesis that depends on the incident light wavelength, but that dependence can be canceled by the presence of radio-frequency (RF) electromagnetic fields. The present manuscript has as its aim to study the effect of light wavelength and RF fields on the U-turn time of ‘Candidatus Magnetoglobus multicellularis’, a behavior more related to magnetotaxis. As the experiments were performed during the night, the microorganisms were greater in size than normal, indicating that they were in the process of division. Our results show that when normal in size, the microorganism’s U-turn time is modified by the light wavelength (lower for blue light than for green and red light), but RF fields do not affect that U-turn time dependence on the light wavelength. For the microorganism in the process of division, we describe for the first time how the photokinesis and U-turn time dependence on the light wavelength disappear. It is proposed that methyl-accepting chemotaxis proteins are involved in that light wavelength dependence for the U-turn time, but still more studies are necessary to understand how RF fields cancel the photokinesis light wavelength dependence, but do not affect the dependence of the U-turn time. Keywords Magnetotaxis · Multicellular magnetotactic prokaryote · Radical pair mechanism · U-turn · Monochromatic light · Photokinesis
Introduction Magnetotaxis is the passive response to magnetic fields observed in a group of bacteria known as magnetotactic bacteria (MTB). Among the known MTB, there are a group of multicellular organisms known as Multicellular Magnetotactic Prokaryotes (MMP). There are two types: the spherical (sMMP) and the ellipsoidal (eMMP) (Abreu and Acosta-Avalos 2018). sMMP microorganisms are well studied and are found in almost all continents. ‘Candidatus Magnetoglobus multicellularis’ (CMM) is a sMMP found in Rio de Janeiro, Brazil. It has a diameter of about 7 μm (between 5 μm and 9 μm) and is formed by an average number of 17 MTB, each one biomineralizing greigite * Daniel Acosta‑Avalos [email protected] 1
Centro Brasileiro de Pesquisas Físicas, CBPF, Rua Xavier Sigaud 150, Urca, Rio de Janeiro, RJ 22290‑180, Brazil
magnetosomes arranged in linear chains (Abreu et al. 2007). The MTB composing the CMM are Gram-negative cells distributed in a spherical helix, being the helix axis the CMM motion axis (Keim et al. 2006). Phylogenetic analyses based on 16S rRNA genes sequences have shown that CMM is related to sulfate-reducing bacteria from the Deltapr
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