Bacterial symbiont diversity in Arctic seep Oligobrachia siboglinids

Animal Microbiome

Research

Arunima Sen¹  Gwenn Tanguy²  Ann C. Andersen³  Stéphane Hourdez⁴  Pierre E. Galand⁴ 

[1] Department of Arctic Biology, The University Centre in Svalbard (UNIS), Longyearbyen, Norway;Faculty of Bioscience and Aquaculture, Nord University, Bodø, Norway;FR2424 Sorbonne Université-CNRS, Genomer, Station Biologique de Roscoff, Roscoff, France;UMR7144 Laboratoire Adaptation et Diversité en Milieu Marin (AD2M), Sorbonne Université-CNRS, Station Biologique de Roscoff, Roscoff, France;UMR8222 Laboratoire d’Ecogéochimie des Environnements Benthiques (LECOB), CNRS-Sorbonne Université, Observatoire Océanologique, Banyuls-Sur-Mer, France;

关键词: Frenulates;    Chemosynthesis;    Methane;    Sulfur oxidation;    Metabarcoding;    Cold seeps;   

DOI  :  10.1186/s42523-023-00251-x

 received in 2022-04-11, accepted in 2023-05-15,  发布年份 2023

来源: Springer

【 摘 要 】

BackgroundHigh latitude seeps are dominated by Oligobrachia siboglinid worms. Since these worms are often the sole chemosymbiotrophic taxon present (they host chemosynthetic bacteria within the trophosome organ in their trunk region), a key question in the study of high latitude seep ecology has been whether they harbor methanotrophic symbionts. This debate has manifested due to the mismatch between stable carbon isotope signatures of the worms (lower than -50‰ and usually indicative of methanotrophic symbioses) and the lack of molecular or microscopic evidence for methanotrophic symbionts. Two hypotheses have circulated to explain this paradox: (1) the uptake of sediment carbon compounds with depleted δC13 values from the seep environment, and (2) a small, but significant and difficult to detect population of methanotrophic symbionts. We conducted 16S rRNA amplicon sequencing of the V3-V4 regions on two species of northern seep Oligobrachia (Oligobrachia webbi and Oligobrachia sp. CPL-clade), from four different high latitude sites, to investigate the latter hypothesis. We also visually checked the worms’ symbiotic bacteria within the symbiont-hosting organ, the trophosome, through transmission electron microscopy.ResultsThe vast majority of the obtained reads corresponded to sulfide-oxidizers and only a very small proportion of the reads pertained to methane-oxidizers, which suggests a lack of methanotrophic symbionts. A number of sulfur oxidizing bacterial strains were recovered from the different worms, however, host individuals tended to possess a single strain, or sometimes two closely-related strains. However, strains did not correspond specifically with either of the two Oligobrachia species we investigated. Water depth could play a role in determining local sediment bacterial communities that were opportunistically taken up by the worms. Bacteria were abundant in non-trophosome (and thereby symbiont-free) tissue and are likely epibiotic or tube bacterial communities.ConclusionsThe absence of methanotrophic bacterial sequences in the trophosome of Arctic and north Atlantic seep Oligobrachia likely indicates a lack of methanotrophic symbionts in these worms, which suggests that nutrition is sulfur-based. This is turn implies that sediment carbon uptake is responsible for the low δ13C values of these animals. Furthermore, endosymbiotic partners could be locally determined, and possibly only represent a fraction of all bacterial sequences obtained from tissues of these (and other) species of frenulates.

【 授权许可】

CC BY   
© The Author(s) 2023

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Fig. 3