<i>Pelomyxa doughnuta</i> sp. nov. (Archamoebea, Pelobiontida) with an unusual nucleus‐glycogen association

Pelomyxa is a genus of anaerobic amoebae that live in consortia with multiple prokaryotic endosymbionts. Although the symbionts represent a large fraction of the cellular biomass, their metabolic roles have not been investigated. Using single-cell genomics and transcriptomics, we have characterized the prokaryotic community associated with P. schiedti, which is composed of two bacteria, Candidatus Syntrophus pelomyxae (class Deltaproteobacteria) and Candidatus Vesiculincola pelomyxae (class Clostridia), and a methanogen, Candidatus Methanoregula pelomyxae. Fluorescence in situ hybridization and electron microscopy showed that Ca. Vesiculincola pelomyxae is localized inside vesicles, whereas the other endosymbionts occur freely in the cytosol, with Ca. Methanoregula pelomyxae enriched around the nucleus. Genome and transcriptome-based reconstructions of the metabolism suggests that the cellulolytic activity of P. schiedti produces simple sugars that fuel its own metabolism and the metabolism of a Ca. Vesiculincola pelomyxae, while Ca. Syntrophus pelomyxae energy metabolism relies on degradation of butyrate and isovalerate from the environment. Both species of bacteria and the ameba use hydrogenases to transfer the electrons from reduced equivalents to hydrogen, a process that requires a low hydrogen partial pressure. This is achieved by the third endosymbiont, Ca. Methanoregula pelomyxae, which consumes H2 and formate for methanogenesis. While the bacterial symbionts can be successfully eliminated by vancomycin treatment without affecting the viability of the amoebae, treatment with 2-bromoethanesulfonate, a specific inhibitor of methanogenesis, killed the amoebae, indicating the essentiality of the methanogenesis for this consortium.

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Unusual archamoeba Pelomyxa pilosa sp. nov. (Amoebozoa: Archamoebae: Pelobiontida): a light and electron microscopic study

Chistyakova,

Frolov,

Radaev

et al. 2024

Zoosystematica Rossica

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This paper presents the results of a study and describes a new species of pelobionts, Pelomyxa pilosa sp. nov. (Archamoebae: Pelobiontida). This species was found in the bottom sediments of a pond near St Petersburg (Russia) and was examined using light, immunofluorescence, and transmission electron microscopy. It is placed in the genus Pelomyxa Greeff, 1874 based on a combination of morphological features, including the mode of locomotion, the presence of numerous flagella, the organisation of the cytoplasm, and the presence of obligate prokaryotic endocytobionts. The new species can be easily distinguished from congeners by the specific presence of numerous prokaryotic ectobionts on the cell surface and the organisation of the nuclear apparatus. The nucleolar material in this species forms a hollow sphere consisting of tightly adjacent patches of various shapes and sizes, surrounded by granular material.

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Pelomyxa doughnuta sp. nov. (Archamoebea, Pelobiontida) with an unusual nucleus‐glycogen association

Cited by 3 publications

References 20 publications

Glomerulosomes: morphologically distinct nuclear organelles of unknown nature

Glomerulosomes: morphologically distinct nuclear organelles of unknown nature

Hydrogenotrophic methanogenesis is the key process in the obligately syntrophic consortium of the anaerobic ameba Pelomyxa schiedti

Unusual archamoeba Pelomyxa pilosa sp. nov. (Amoebozoa: Archamoebae: Pelobiontida): a light and electron microscopic study

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