Short-Term Exposure to Sterile Seawater Reduces Bacterial Community Diversity in the Sea Anemone, Exaiptasia diaphana

Ashley M Dungan,Madeleine J H Van Oppen,Linda L Blackall

doi:10.3389/fmars.2020.599314

Ashley M Dungan, Madeleine J H Van Oppen + Show 1 more

Open Access

https://doi.org/10.3389/fmars.2020.599314

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Abstract

The global decline of coral reefs heightens the need to understand how corals may persist under changing environmental conditions. Restructuring of the coral-associated bacterial community, either through natural or assisted strategies, has been suggested as a means of adaptation to climate change. A low complexity microbial system would facilitate testing the efficacy of microbial restructuring strategies. We used the model organism for corals,Exaiptasia diaphana, and determined that short-term (3 weeks) exposure to filter-sterilized seawater conditions alone reduced the complexity of the microbiome. Metabarcoding of the V5–V6 region of the bacterial 16S rRNA gene revealed that alpha diversity was approximately halved in anemones reared in filter-sterilized seawater compared to controls reared in unfiltered seawater and that the composition (beta diversity) differed significantly between the two. By reducing the complexity of theE. diaphanamicrobiome, the development of a system for testing assisted strategies such as probiotics, is more feasible.

Highlights

Corals are colonized by microbes, including bacteria, eukaryotes, archaea, and viruses (Blackall et al, 2015; Ainsworth et al, 2017; Huggett and Apprill, 2019), that contribute to the overall health of this complex host-microbe association, or holobiont (Rohwer et al, 2002)
We found that the bacterial diversity and community structure for each of four anemone genotypes was significantly different with a reduction in alpha diversity when anemones were moved from RSS to fRSS and maintained in fRSS for 3 weeks
The taxa we identified as stably associated with E. diaphana can be divided into those that are frequently found in cnidarians or their algal symbionts, including Alteromonadaceae (Rothig et al, 2017; Ahmed et al, 2019; Damjanovic et al, 2019a; Epstein et al, 2019b), Labrenzia (Lawson et al, 2017), Fulvivirga (Glasl et al, 2016; Ziegler et al, 2017; Epstein et al, 2019b; Pootakham et al, 2019; Damjanovic et al, 2020) and Sphingobacteriales (Meron et al, 2012; Kellogg et al, 2013; Li et al, 2014; van de Water et al, 2017; Bonthond et al, 2018), and those that occur much more infrequently, including Terasakiellaceae, Coxiella, and Nannocystaceae

Summary

Introduction

Corals are colonized by microbes, including bacteria, eukaryotes, archaea, and viruses (Blackall et al, 2015; Ainsworth et al, 2017; Huggett and Apprill, 2019), that contribute to the overall health of this complex host-microbe association, or holobiont (Rohwer et al, 2002). Manipulation of the coral microbiome could be achieved through the addition of a bacterial consortium with specific purposes such as degradation of oil (dos Santos et al, 2015), nutrient cycling, disease prevention (Alagely et al, 2011), or mitigation of bleaching (Rosado et al, 2018). These consortia, known as probiotics, are developed to target specific

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