Characterization of a Neochlamydia-like bacterium associated with epitheliocystis in cultured Arctic charr Salvelinus alpinus

Andrew Draghi, Julie Bebak, Vsevolod Popov, Alicia C. Noble, Steven J. Geary, A. Brian West, Philip Byrne, Salvatore Frasca

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Infections of branchial epithelium by intracellular gram-negative bacteria, termed epitheliocystis, have limited culture of Arctic charr Salvelinus alpinus. To characterize a bacterium associated with epitheliocystis in cultured charr, gills were sampled for histopathologic examination, conventional and immunoelectron microscopy, in situ hybridization, 16S ribosomal DNA (rDNA) amplification, sequence analysis and phylogenetic inference. Sampling was conducted at the Freshwater Institute (Shepherdstown, West Virginia, USA) during outbreaks of epitheliocystis in April and May 2002. Granular, basophilic, cytoplasmic inclusions in charr gill were shown to stain with Macchiavello, Lendrum's phloxine-tartrazine and Gimenez histochemical techniques. Ultrastructurally, inclusions were membrane-bound and contained round to elongate reticulate bodies that were immunoreactive to an antibody against chlamydial lipopolysaccharide, suggesting the presence of similar epitopes. DNA extracted from gills supported amplification of the most polymorphic and phylogenetically relevant region of the 16S rRNA gene, which had 97 to 100% identity with several uncultured clinical Neochlamydia spp. (order Chlamydiales) Clones WB13 (AY225593.1) and WB258 (AY225594.1). Sequence-specific riboprobes localized to inclusions during in situ hybridization experiments. Taxonomic affiliation was inferred by distance- and parsimony-based phylogenetic analyses of the 16S sequence, which branched with Neochlamydia hartmannellae in the order Chlamydiales with high confidence. This is the first molecular characterization of a chlamydia associated with epitheliocystis in Arctic charr and the fourth Neochlamydia spp. sequence to be associated with epitheliocystis. Presence of a clinical neochlamydial sequence, first identified from a cat, in Arctic charr suggests a possible mammalian and piscine host range for some environmental chlamydiae.

Original languageEnglish (US)
Pages (from-to)27-38
Number of pages12
JournalDiseases of Aquatic Organisms
Volume76
Issue number1
StatePublished - Jun 7 2007

Fingerprint

Neochlamydia
Salvelinus alpinus
amplification
Chlamydiales
phylogenetics
DNA
gills
bacterium
host range
bacteria
in situ hybridization
antibody
microscopy
clone
membrane
cytoplasmic inclusions
Chlamydia
gene
phylogeny
sampling

Keywords

  • 16S ribosomal RNA gene
  • Arctic charr
  • Environmental chlamydiae
  • Epitheliocystis
  • In situ hybridization
  • Neochlamydia
  • Salvelinus
  • Ultrastructure

ASJC Scopus subject areas

  • Aquatic Science
  • Ecology

Cite this

Characterization of a Neochlamydia-like bacterium associated with epitheliocystis in cultured Arctic charr Salvelinus alpinus. / Draghi, Andrew; Bebak, Julie; Popov, Vsevolod; Noble, Alicia C.; Geary, Steven J.; West, A. Brian; Byrne, Philip; Frasca, Salvatore.

In: Diseases of Aquatic Organisms, Vol. 76, No. 1, 07.06.2007, p. 27-38.

Research output: Contribution to journalArticle

Draghi, A, Bebak, J, Popov, V, Noble, AC, Geary, SJ, West, AB, Byrne, P & Frasca, S 2007, 'Characterization of a Neochlamydia-like bacterium associated with epitheliocystis in cultured Arctic charr Salvelinus alpinus', Diseases of Aquatic Organisms, vol. 76, no. 1, pp. 27-38.
Draghi, Andrew ; Bebak, Julie ; Popov, Vsevolod ; Noble, Alicia C. ; Geary, Steven J. ; West, A. Brian ; Byrne, Philip ; Frasca, Salvatore. / Characterization of a Neochlamydia-like bacterium associated with epitheliocystis in cultured Arctic charr Salvelinus alpinus. In: Diseases of Aquatic Organisms. 2007 ; Vol. 76, No. 1. pp. 27-38.
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abstract = "Infections of branchial epithelium by intracellular gram-negative bacteria, termed epitheliocystis, have limited culture of Arctic charr Salvelinus alpinus. To characterize a bacterium associated with epitheliocystis in cultured charr, gills were sampled for histopathologic examination, conventional and immunoelectron microscopy, in situ hybridization, 16S ribosomal DNA (rDNA) amplification, sequence analysis and phylogenetic inference. Sampling was conducted at the Freshwater Institute (Shepherdstown, West Virginia, USA) during outbreaks of epitheliocystis in April and May 2002. Granular, basophilic, cytoplasmic inclusions in charr gill were shown to stain with Macchiavello, Lendrum's phloxine-tartrazine and Gimenez histochemical techniques. Ultrastructurally, inclusions were membrane-bound and contained round to elongate reticulate bodies that were immunoreactive to an antibody against chlamydial lipopolysaccharide, suggesting the presence of similar epitopes. DNA extracted from gills supported amplification of the most polymorphic and phylogenetically relevant region of the 16S rRNA gene, which had 97 to 100{\%} identity with several uncultured clinical Neochlamydia spp. (order Chlamydiales) Clones WB13 (AY225593.1) and WB258 (AY225594.1). Sequence-specific riboprobes localized to inclusions during in situ hybridization experiments. Taxonomic affiliation was inferred by distance- and parsimony-based phylogenetic analyses of the 16S sequence, which branched with Neochlamydia hartmannellae in the order Chlamydiales with high confidence. This is the first molecular characterization of a chlamydia associated with epitheliocystis in Arctic charr and the fourth Neochlamydia spp. sequence to be associated with epitheliocystis. Presence of a clinical neochlamydial sequence, first identified from a cat, in Arctic charr suggests a possible mammalian and piscine host range for some environmental chlamydiae.",
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