Bacterial Communities in Tissues and Surficial Mucus of the Cold-Water Coral Paragorgia arborea

Abstract

Coral bacterial associates can play important functional roles for the holobiont, such as nitrogen cycling, nutrient processing, and supporting immunity. While bacteria found within the microbiome of corals may benefit the host, they can also be linked to pathogenesis. In the deep-sea, cold-water corals, like their warm shallowwater counterparts, host bacterial communities, but have received little attention due to logistical constraints in sampling. In particular, bacteria associated with surficial mucus of cold-water corals have not yet been investigated. Here, tissue and mucus samples of Paragorgia arborea were collected from three submarine canyons along the continental slope of the Gulf of Maine. Bacterial DNA was extracted from tissue and mucus samples and sequencing of the V6-V8 hypervariable region of the 16S rRNA gene was performed using Illumina MiSeq. The bacterial communities associated with P. arborea compartments (tissue and mucus) and sampling locations (canyon) differed significantly in composition. Proteobacteria, Tenericutes, and Spirochaetes were the dominant phyla across the majority of coral tissue samples, with Gammaproteobacteria and Alphaproteobacteria identified as the largest Proteobacteria contributors across all samples. Operational taxonomic units (OTUs) belonging to the taxa Spirochaeta, Mycoplasma, Flavobacteriaceae, Terasakiellaceae, Campylobacterales, and Rickettsiales were identified as biomarkers (bacterial taxa significantly more abundant in a specific coral microhabitat) of P. arborea tissues, while Paracoccus was a biomarker of P. arborea mucus. Many of the recovered biomarker taxa may be involved in nitrogen cycling. Representatives from several bacterial families (Vibrionaceae, Campylobacteraceae, Rhodobacteraceae, Flavobacteriaceae, and Burkholderiaceae) previously reported in diseased scleractinians, were present in P. arborea as rare bacterial taxa. Characterizing the bacterial associates present in visibly healthy coral colonies provides a benchmark of dominant and rare bacterial groups present in the cold-water coral holobiont. This is the first characterization of bacterial groups associated with P. arborea, examining both tissue-and mucus-specific communities.

Differential Patterns of Microbiota Recovery in Symbiotic and Aposymbiotic Corals following Antibiotic Disturbance

“…Because these are not common bacteria in seawater, they may be specific to the A. poculata mucus and require transfer from other A. poculata colonies or other hosts for recolonization. Consistent with this idea, Terasakiellaceae are commonly associated with the cold-water coral Paragorgia arborea (39). Future experiments in which disturbed A. poculata colonies are exposed to untreated A. poculata colonies are needed to address the hypothesis that disturbed colonies can recruit microbes from other neighboring, healthy colonies.…”

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

“…Terasakiellaceae (Rhodospirallales) were reported in the cold water coral Paragorgia arborea (Weiler et al, 2018) where they were implicated in nitrogen cycling, and they could have a similar role in the anemone holobiont. Coxiella are members of the order Legionellales, which are described as facultative or obligate intracellular parasites known to infect invertebrate and vertebrate species (Garrity and Brenner, 2005), including marine animals; their role in anemones should be determined.…”

Influence of temperature changes on symbiotic Symbiodiniaceae and bacterial communities’ structure: an experimental study on soft coral Sarcophyton trocheliophorum (Anthozoa: Alcyoniidae)

“…According to our results, Tenericutes and Firmicutes have been replaced with Proteobacteria and Bacteroidetes by cooling stress, while there was non-significant change in bacterial community's structure after cooling in Ig, statistically. Furthermore, bacterial families, including Rhodobacteraceae, Vibrionaceae, Flavobacteriaceae, Burkholderiaceae, and Campylobacteraceae were formerly reported in high abundance in diseased corals (Daniels et al 2015, Weiler et al 2018. Within this group, pathogenicity of Rhodobacteraceae is considerable (Roder et al 2014, Sunagaw et al 2009.…”

“…This evidenced that long-term temperature changes can provide suitable adaptation situations for bacterial communities to prevent the effect of short-term changes. Weiler et al (2018) proved the bacterial compositions of seawater were dissimilar with communities of host corals. We cautiously suggest that environmental alterations may cause primary symbiotic communities structure; and in this condition, bacteria in surrounding seawater cannot play an important role in new communities' composition.…”