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Tick-Bacteria Mutualism Depends on B Vitamin Synthesis Pathways

Abstract : Mutualistic interactions with microbes have facilitated the radiation of major eukaryotic lineages [1, 2]. Microbes can notably provide biochemical abilities, allowing eukaryotes to adapt to novel habitats or to specialize on particular feeding niches [2-4]. To investigate the importance of mutualisms for the exclusive blood feeding habits of ticks, we focused on a bacterial genus of medical interest, Francisella, which is known to include both virulent intracellular pathogens of vertebrates [5, 6] and maternally inherited symbionts of ticks [7-9]. Through a series of physiological experiments, we identified a Francisella type, F-Om, as an obligate nutritional mutualist in the life cycle of the African soft tick Ornithodoros moubata. Francisella F-Om mutualism synthesizes B vitamins that are deficient in the blood meal of ticks. Indeed, experimental elimination of Francisella F-Omresulted in alteration of tick life history traits and physical abnormalities, deficiencies which were fully restored with an oral supplement of B vitamins. We also show that Francisella F-Om is maternally transmitted to all maturing tick oocytes, suggesting that this heritable symbiont is an essential adaptive element in the life cycle of O. moubata. The Francisella F-Om genome further revealed a recent origin from a Francisella pathogenic life style, as observed in other Francisella symbionts [6, 7, 10]. Though half of its protein-coding sequences are now pseudogenized or lost, Francisella F-Om has kept several B vitamin synthesis pathways intact, confirming the importance of these genes in evolution of its nutritional mutualism with ticks.
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https://hal.archives-ouvertes.fr/hal-01933362
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Submitted on : Friday, November 23, 2018 - 4:35:06 PM
Last modification on : Tuesday, May 26, 2020 - 2:59:00 PM

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Olivier Duron, Olivier Morel, Valérie Noël, Marie Buysse, Florian Binetruy, et al.. Tick-Bacteria Mutualism Depends on B Vitamin Synthesis Pathways. Current Biology - CB, Elsevier, 2018, 28 (12), pp.1896 - 1902.e5. ⟨10.1016/j.cub.2018.04.038⟩. ⟨hal-01933362⟩

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