Collective magnetotaxis of microbial holobionts is optimized by the three-dimensional organization and magnetic properties of ectosymbionts.

Chevrier, Daniel M ORCID: 0000-0002-0914-6714, Juhin, Amélie ORCID: 0000-0003-0752-3034, Menguy, Nicolas ORCID: 0000-0003-4613-2490, Bolzoni, Romain ORCID: 0000-0002-5741-3856, Soto-Rodriguez, Paul ED ORCID: 0000-0002-2425-932X, Kojadinovic-Sirinelli, Mila ORCID: 0000-0001-8110-3113, Paterson, Greig A ORCID: 0000-0002-6864-7420, Belkhou, Rachid ORCID: 0000-0002-2218-7481, Williams, Wyn ORCID: 0000-0001-9210-7574, Skouri-Panet, Fériel ORCID: 0000-0002-2623-9058
et al (show 7 more authors) (2023) Collective magnetotaxis of microbial holobionts is optimized by the three-dimensional organization and magnetic properties of ectosymbionts. Proceedings of the National Academy of Sciences of the United States of America, 120 (10). e2216975120-.

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Over the last few decades, symbiosis and the concept of holobiont-a host entity with a population of symbionts-have gained a central role in our understanding of life functioning and diversification. Regardless of the type of partner interactions, understanding how the biophysical properties of each individual symbiont and their assembly may generate collective behaviors at the holobiont scale remains a fundamental challenge. This is particularly intriguing in the case of the newly discovered magnetotactic holobionts (MHB) whose motility relies on a collective magnetotaxis (i.e., a magnetic field-assisted motility guided by a chemoaerotaxis system). This complex behavior raises many questions regarding how magnetic properties of symbionts determine holobiont magnetism and motility. Here, a suite of light-, electron- and X-ray-based microscopy techniques [including X-ray magnetic circular dichroism (XMCD)] reveals that symbionts optimize the motility, the ultrastructure, and the magnetic properties of MHBs from the microscale to the nanoscale. In the case of these magnetic symbionts, the magnetic moment transferred to the host cell is in excess (10<sup>2</sup> to 10<sup>3</sup> times stronger than free-living magnetotactic bacteria), well above the threshold for the host cell to gain a magnetotactic advantage. The surface organization of symbionts is explicitly presented herein, depicting bacterial membrane structures that ensure longitudinal alignment of cells. Magnetic dipole and nanocrystalline orientations of magnetosomes were also shown to be consistently oriented in the longitudinal direction, maximizing the magnetic moment of each symbiont. With an excessive magnetic moment given to the host cell, the benefit provided by magnetosome biomineralization beyond magnetotaxis can be questioned.

Item Type: Article
Uncontrolled Keywords: Biophysics, Electrons, Physical Phenomena, Biomineralization
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 13 Mar 2023 11:23
Last Modified: 01 Sep 2023 05:04
DOI: 10.1073/pnas.2216975120
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