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Emerging pathogens of gilthead seabream: characterisation and genomic analysis of novel intracellular β-proteobacteria


Seth-Smith, Helena M B; Dourala, Nancy; Fehr, Alexander; Qi, Weihong; Katharios, Pantelis; Ruetten, Maja; Mateos, José M; Nufer, Lisbeth; Weilenmann, Roseline; Ziegler, Urs; Thomson, Nicholas R; Schlapbach, Ralph; Vaughan, Lloyd (2016). Emerging pathogens of gilthead seabream: characterisation and genomic analysis of novel intracellular β-proteobacteria. The ISME journal, 10(7):1791-1803.

Abstract

New and emerging environmental pathogens pose some of the greatest threats to modern aquaculture, a critical source of food protein globally. As with other intensive farming practices, increasing our understanding of the biology of infections is important to improve animal welfare and husbandry. The gill infection epitheliocystis is increasingly problematic in gilthead seabream (Sparus aurata), a major Mediterranean aquaculture species. Epitheliocystis is generally associated with chlamydial bacteria, yet we were not able to localise chlamydial targets within the major gilthead seabream lesions. Two previously unidentified species within a novel β-proteobacterial genus were instead identified. These co-infecting intracellular bacteria have been characterised using high-resolution imaging and genomics, presenting the most comprehensive study on epitheliocystis agents to date. Draft genomes of the two uncultured species, Ca. Ichthyocystis hellenicum and Ca. Ichthyocystis sparus, have been de novo sequenced and annotated from preserved material. Analysis of the genomes shows a compact core indicating a metabolic dependency on the host, and an accessory genome with an unprecedented number of tandemly arrayed gene families. This study represents a critical insight into novel, emerging fish pathogens and will be used to underpin future investigations into the bacterial origins, and to develop diagnostic and treatment strategies.

Abstract

New and emerging environmental pathogens pose some of the greatest threats to modern aquaculture, a critical source of food protein globally. As with other intensive farming practices, increasing our understanding of the biology of infections is important to improve animal welfare and husbandry. The gill infection epitheliocystis is increasingly problematic in gilthead seabream (Sparus aurata), a major Mediterranean aquaculture species. Epitheliocystis is generally associated with chlamydial bacteria, yet we were not able to localise chlamydial targets within the major gilthead seabream lesions. Two previously unidentified species within a novel β-proteobacterial genus were instead identified. These co-infecting intracellular bacteria have been characterised using high-resolution imaging and genomics, presenting the most comprehensive study on epitheliocystis agents to date. Draft genomes of the two uncultured species, Ca. Ichthyocystis hellenicum and Ca. Ichthyocystis sparus, have been de novo sequenced and annotated from preserved material. Analysis of the genomes shows a compact core indicating a metabolic dependency on the host, and an accessory genome with an unprecedented number of tandemly arrayed gene families. This study represents a critical insight into novel, emerging fish pathogens and will be used to underpin future investigations into the bacterial origins, and to develop diagnostic and treatment strategies.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Center for Microscopy and Image Analysis
04 Faculty of Medicine > Functional Genomics Center Zurich
05 Vetsuisse Faculty > Institute of Veterinary Pathology
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
610 Medicine & health
Language:English
Date:July 2016
Deposited On:18 Jan 2017 16:29
Last Modified:28 Feb 2017 04:09
Publisher:Nature Publishing Group
ISSN:1751-7362
Funders:Marie Curie IEF grant number 332058 to HMBSS, FP7 Aquaexcel-TNA project 01-05-15-0004-B to LV and PK.
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1038/ismej.2015.223
PubMed ID:26849311

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