Microbiome characterization of defensive tissues in the model anemone Exaiptasia diaphana

Justin Maire,Linda L Blackall,Madeleine J H Van Oppen

doi:10.1186/s12866-021-02211-4

Justin Maire, Linda L Blackall + Show 1 more

Open Access

https://doi.org/10.1186/s12866-021-02211-4

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Abstract

BackgroundCoral 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.ResultsUsing 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.ConclusionsThis 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.

Highlights

Coral reefs are among the most diverse and productive ecosystems on Earth
E. diaphana’s acontia associate with Symbiodiniaceae and bacteria To evaluate the presence of microorganisms in E. diaphana, acontia ejection was triggered by poking anemones and acontia were subsequently dissected and observed with confocal laser scanning microscopy (CSLM)
A total of 150 bacteria colonies were isolated from agar culture plates on which the dissected and homogenized acontia of the four anemone genotypes were spread

Summary

Introduction

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. Coral reefs provide us with countless benefits by supporting fisheries, tourism and coastal development, and their value is estimated to 9.9 trillion USD/year [1] They are among the most diverse ecosystems in the world and are home to more than 25% of marine species, making them a hallmark of biodiversity [2, 3]. Only a handful of studies have compared community structure in the different body parts of the polyp [23, 28, 29], where a high variability across the different compartments was found

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