Structure and temporal dynamics of the bacterial communities associated to microhabitats of the coral Oculina patagonica

Abstract

Originality-significance statement: Corals are known to contain a diverse microbiota that plays a paramount role in the physiology and health of holobiont. However, few studies have addressed the variability of bacterial communities within the coral host. This is precisely the central point of our work, which makes it different from previous characterizations of coral microbiotas. We have characterized the bacterial community composition from mucus, tissue and skeleton of the coral Oculina patagonica, seasonally and at two locations in the Western Mediterranean Sea, to further understand how environmental conditions and the coral microbiome structure are related.This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an 'Accepted Article', doi: 10.1111/1462-2920.13548This article is protected by copyright. All rights reserved. 2 AbstractCorals are known to contain a diverse microbiota that plays a paramount role in the physiology and health of holobiont. However, few studies have addressed the variability of bacterial communities within the coral host. In this study, bacterial community composition from the mucus, tissue and skeleton of the scleractinian coral Oculina patagonica were investigated seasonally at two locations in the Western Mediterranean Sea, to further understand how environmental conditions and the coral microbiome structure are related.We used denaturing gradient gel electrophoresis in combination with next-generation sequencing and electron microscopy to characterize the bacterial community. The bacterial communities were significantly different among coral compartments, and coral tissue displayed the greatest changes related to environmental conditions and coral health status.Species belonging to the Rhodobacteraceae and Vibrionaceae families form part of O.patagonica tissues core microbiome and may play significant roles in the nitrogen cycle.Furthermore, sequences related to the coral pathogens, Vibrio mediterranei and Vibrio coralliilyticus, were detected not only in bleached corals but also in healthy ones, even during cold months. This fact opens a new view onto unveiling the role of pathogens in the development of coral diseases in the future.

The low diverse gastric microbiome of the jellyfish Cotylorhiza tuberculata is dominated by four novel taxa

“…In addition, Tenacibaculum ‐like, Spiroplasma ‐like and Mycoplasma ‐like bins that had already been detected in our previous study (Cortés‐Lara et al ., ), were retrieved in the metagenomics analysis. It is not unusual that metagenomics retrieves phylotypes not detected by 16S rRNA gene amplicon sequencing, since this method is not submitted to specific primer amplification biases and the impact of high ribosomal operon copy numbers (Logares et al ., ; Rubio‐Portillo et al ., ).…”

Diazotrophic community and associated dinitrogen fixation within the temperate coral Oculina patagonica

“…The animal tissue and skeleton are hotspots for DDN assimilation and the relative high abundance of autotrophic Cyanobacteria and Chlorobia suggest that they may be key members of the diazotrophic community. This corroborates previous predictive metagenomic analysis showing that metabolic functions linked to the N cycle are highly abundant in the core microbiome of O. patagonica (Rubio‐Portillo et al ., ). We suggest that (i) autotrophic diazotrophs may provide a source of both C and N to the coral symbiosis and that (ii) DDN possibly supports the rapid proliferation of an endolithic algal community in bleached corals.…”

“…Here, we provide a first description of the diazotrophic community associated with the temperate coral O. patagonica from the Mediterranean Sea. The overall microbiota of O. patagonica showed a strong compartmentalization between the tissue and mucus microhabitats which is consistent with previous reports describing that the tissue‐associated bacterial communities are generally more abundant and diverse compared with the mucus (Koren and Rosenberg, ; Rubio‐Portillo et al ., ). Here, the most dominant bacterial groups within the tissue belonged to Cyanobacteria as well as Alphaproteobacteria of the orders Rhizobiales, Rhodospirillales and Rhodobacterales, which are known to contain putative diazotrophs associated with tropical corals (Lema et al ., ; Lesser et al ., ), and thus may also play a key role for N 2 fixation within O. patagonica .…”

“…Under the oligotrophic conditions of the Eastern south basin, it was demonstrated, using isotopically labelled bicarbonate, that bleached portions of O. patagonica colonies benefit from two alternative photosynthate sources, that are translocated (i) intracolonially from non‐bleached tissue portions (Fine et al ., ) and (ii) from the skeletal endolithic community (Fine and Loya, ). Both, the endolithic and the tissue‐associated bacterial communities of O. patagonica contain cyanobacteria (Ainsworth et al ., ; Rubio‐Portillo et al ., ) that may be able to transfer not only photosynthates as demonstrated, but also DDN and supply the coral host with beneficial carbon (C) and N sources during bleaching. While we have recently observed that coral‐associated diazotrophs may function as additional N source for tropical corals, particularly during oligotrophic conditions or bleaching, information on corals from temperate regions is lacking.…”

Biogeographic Comparison of Lophelia-Associated Bacterial Communities in the Western Atlantic Reveals Conserved Core Microbiome

“…This technique uses a reference phylogeny of completed bacterial genomes to predict the genomic copy number of each gene family, and those gene families have been linked with experimental evidence of functionality. While the quality of the predictions is directly related to how many relevant environmental bacterial genomes are available in the database, this technique has been increasingly applied to temperate and tropical coral systems (Ainsworth et al, 2015; Morrow et al, 2015; Rubio-Portillo et al, 2016; van de Water et al, 2016; Zaneveld et al, 2016). …”