Replicating phages in the epidermal mucosa of the eel (Anguilla anguilla).

Miguel Carda-Diã©Guez,Carolina Megumi Mizuno,Francisco Rodriguez-Valera,Carmen Amaro,Rohit Ghai

doi:10.3389/fmicb.2015.00003

Miguel Carda-Diã©Guez, Carolina Megumi Mizuno + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2015.00003

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Abstract

In this work, we used the eel (Anguilla anguilla) as an animal model to test the hypothesis of Barr et al. (2013a,b) about the putative role of the epidermal mucosa as a phage enrichment layer. To this end, we analyzed the microbial content of the skin mucus of wild and farmed eels by using a metagenomic approach. We found a great abundance of replicating phage genomes (concatemers) in all the samples. They were assembled in four complete genomes of three Myovirus and one Podovirus. We also found evidences that ΦKZ and Podovirus phages could be part of the resident microbiota associated to the eel mucosal surface and persist on them over the time. Moreover, the viral abundance estimated by epiflorescent counts and by metagenomic recruitment from eel mucosa was higher than that of the surrounding water. Taken together, our results support the hypothesis that claims a possible role of phages in the animal mucus as agents controlling bacterial populations, including pathogenic species, providing a kind of innate immunity.

Highlights

Animals, including humans, protect their mucous membranes by covering them with a mucus layer that contains microcidal and microstatic compounds produced by epidermis-associated immune cells
The assembly of the Illumina datasets yielded a total of 17 viral contigs >10 kb and 23 contigs 98% nucleotide identity) to the longer contigs (Figure S2)
In order to check if any of the assembled phages represented complete genomes, we performed all vs all comparisons of these viral contigs

Summary

Introduction

Animals, including humans, protect their mucous membranes by covering them with a mucus layer that contains microcidal and microstatic compounds produced by epidermis-associated immune cells. Fish mucus attracts aquatic bacteria, including pathogens, some of which have chemotactic systems that “sense” mucin, glucids, and other nutrients present in mucus (Valiente et al, 2008). For this reason, fish exposed surfaces are covered by a dense mucus layer enriched in antimicrobial compounds, most of them uncharacterized (Ellis, 2001). The attraction of virus to mucus surfaces has been corroborated in coral mucus using enumeration techniques (Nguyen-Kim et al, 2014) If this hypothesis is true, phages could play a significant role in defense against aquatic pathogens. Caudovirales lytic phages replicate forming genome concatamers that can be larger than the cell genome and provide an ideal subject for direct sequencing and assembly (Mizuno et al, 2013; Rodriguez-Valera et al, 2014)

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