title: Emerging pathogens of gilthead seabream: characterisation and genomic analysis of novel intracellular β-proteobacteria.
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.
authors: Functional Genomics Center Zürich, University of Zürich, Zürich, Switzerland.|Institute for Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors: Helena M B
authors: HM
authors: Seth-Smith
authors: Selonda Aquaculture, Athens, Greece.
authors: Nancy
authors: N
authors: Dourala
authors: Institute for Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors: Alexander
authors: A
authors: Fehr
authors: Functional Genomics Center Zürich, University of Zürich, Zürich, Switzerland.
authors: Weihong
authors: W
authors: Qi
authors: Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Center for Marine Research, Heraklion, Crete, Greece.
authors: Pantelis
authors: P
authors: Katharios
authors: Institute for Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors: Maja
authors: M
authors: Ruetten
authors: Center for Microscopy and Image Analysis, University of Zürich, Zürich, Switzerland.
authors: José M
authors: JM
authors: Mateos
authors: Institute for Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors: Lisbeth
authors: L
authors: Nufer
authors: Institute for Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors: Roseline
authors: R
authors: Weilenmann
authors: Center for Microscopy and Image Analysis, University of Zürich, Zürich, Switzerland.
authors: Urs
authors: U
authors: Ziegler
authors: Pathogen Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK.
authors: Nicholas R
authors: NR
authors: Thomson
authors: Functional Genomics Center Zürich, University of Zürich, Zürich, Switzerland.
authors: Ralph
authors: R
authors: Schlapbach
authors: Institute for Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors: Lloyd
authors: L
authors: Vaughan
mesh_terms: D000818:Animals; D017756:Aquaculture; D020562:Betaproteobacteria / Q000145:classification* / Q000166:cytology / Q000235:genetics; D023281:Genomics; D005880:Gills / Q000382:microbiology; D010802:Phylogeny; D021541:Sea Bream / Q000382:microbiology*