Microbiome characterization of defensive tissues in the model anemone Exaiptasia diaphana

Abstract

Background Coral reefs are among the most diverse and productive ecosystems on Earth. This success relies on the coral’s association with a wide range of microorganisms, including dinoflagellates of the family Symbiodiniaceae that provide coral hosts with most of their organic carbon requirements. While bacterial associates have long been overlooked, research on these microorganisms is gaining traction, and deciphering bacterial identity and function is greatly enhancing our understanding of cnidarian biology. Here, we investigated bacterial communities in defensive tissues (acontia) of the coral model, the sea anemone Exaiptasia diaphana. Acontia are internal filaments that are ejected upon detection of an external threat and release toxins to repel predators. Results Using culturing techniques and 16S rRNA gene metabarcoding we identified bacterial communities associated with acontia of four Great Barrier Reef-sourced E. diaphana genotypes. We show that bacterial communities are similar across genotypes, and dominated by Alteromonadaceae, Vibrionaceae, Rhodobacteraceae, and Saprospiraceae. By analyzing abundant amplicon sequence variants (ASVs) from metabarcoding data from acontia and comparing these to data from whole anemones, we identified five potentially important bacterial genera of the acontia microbiome: Vibrio, Sulfitobacter, Marivita, Alteromonas, and Lewinella. The role of these bacteria within the acontia remains uninvestigated but could entail assistance in defense processes such as toxin production. Conclusions This study provides insight into potential bacterial involvement in cnidarian defense tissues and highlights the need to study bacterial communities in individual compartments within a holobiont.

Transcriptome Sequencing of the Pale Anemones (Exaiptasia diaphana) Revealed Functional Peptide Gene Resources of Sea Anemone

“…Transcriptome technology have recently been applied to explore protein and neuropeptide from several sea anemone species, such as Stichodactyla haddoni, Anemonia sulcata, Exaiptasia pallida, Anthopleura elegantissima, Anthopleura dowii, Heteractis crispa, Cnidopus japonicus, Oulactis sp., Nematostella vectensis, Megalactis griffithsi, and so on (Elran et al, 2014;Macrander et al, 2015;Macrander et al, 2016;Ayala-Sumuano et al, 2017;Madio et al, 2017;Grafskaia et al, 2018;Davey et al, 2019;Mitchell et al, 2020). Exaiptasia diaphana has been commonly used as coral symbiosis study models (Poole et al, 2016;Maire et al, 2021), but responses of its neuropeptide toxins for predation and defense have been barely explored. (Lehnert et al, 2012) encoding genes.…”

Endozoicomonas-chlamydiae interactions in cell-associated microbial aggregates of the coralPocillopora acuta

“…Following PCR, triplicates were pooled, resulting in 45 μL per sample. Metabarcoding library preparation was conducted as previously described ( 70 ) and sequencing was performed at the Walter and Eliza Hall Institute (WEHI) in Melbourne, Australia on one MiSeq V3 system (Illumina) with 2×300bp paired-end reads.…”

Bacterial microbiome variation across symbiotic states and clonal lines in a cnidarian model

“…Previous work has implicated symbiotic state as influential on the anemones' microbiome (Röthig et al, 2016). The acontia of anemones have also been shown to be associated with a unique microbial compared to the whole anemone (Maire et al, 2021). However, studies focusing on microbiome analysis including anemones from distinct genetic backgrounds are scarce.…”

“…Exaiptasia diaphana. Though other studies have previously examined the bacterial microbiome in E. diaphana (Röthig et al, 2016;Dungan et al, 2020;Costa et al, 2021;Maire et al, 2021), this study compares across clonal lines and body part, in addition to algal symbiotic state. Comparing microbiota across genets, which were reared in independent tanks but otherwise identical conditions for years, helps elucidate the role that host genetics may play in structuring bacterial communities.…”

“…Diversity analyses further confirmed microbiome clustering by genotype. While core microbiomes have been identified across genets previously in E. diaphana (Hartman et al, 2020;Maire et al, 2021), these studies sourced genets from similar geographic regions and therefore are likely less genetically distinct than the clonal lines used here, such as CC7 sourced from off the southeastern coast of the United States and H2 and VWB sourced from Hawaii (Sunagawa et al, 2009;Xiang et al, 2013). Previous work in another anemone, Nematostella vectensis, also found differences in bacterial communities across different source populations of animals despite years of laboratory rearing under identical conditions (Mortzfeld et al, 2016).…”