title: Selection and identification of autochthonous potential probiotic bacteria from turbot larvae (Scophthalmus maximus) rearing units.
abstract: The purpose of this study was to select, identify and characterise bacteria as a disease control measure in the rearing of marine fish larvae (turbot, Scophthalmus maximus). Thirty-four out of 400 marine bacterial strains exhibited in vitro anti-bacterial activity against three fish larval pathogens. Two strains originated from culture collections and thirty two strains were isolated directly from turbot larvae rearing units using a pre-selection procedure to facilitate detection of antagonists. Approximately 8,500 colonies from colony-count plates were replica-plated on agar seeded with Vibrio anguillarum, and 196 of them caused zones of clearing in the V. anguillarum agar layer. Of these, 32 strains exhibited reproducible antibacterial properties in vitro when tested against the fish pathogens V. anguillarum 90-11-287, V. splendidus DMC-1 and a Pseudoalteromonas HQ. Seventeen antagonists were identified as Vibrio spp. and four of twelve tested were lethal to yolk-sac larvae. The 15 remaining strains were identified as Roseobacter spp. based on phenotypic criteria and 16S rDNA gene sequence analysis of two strains representing the two major RAPD groups. Most of the remaining 164 strains selected in the initial replica plating were identified as Vibrionaceae or Pseudoalteromonas. Roseobacter spp. were not lethal to egg yolk sac turbot larvae and in two of three trials, the mortality of larvae decreased (p > 0.001) in treatments where 10(7) cfu/ml Roseobacter sp. strain 27-4 was added, indicating a probiotic potential.
authors.affiliation: Danish Institute for Fisheries Research, Department of Seafood Research, c/o Technical University of Denmark, Kgs. Lyngby, Denmark. meh@dfu.min.dk
authors.forename: Mette
authors.initials: M
authors.lastname: Hjelm
authors.forename: Oivind
authors.initials: O
authors.lastname: Bergh
authors.forename: Ana
authors.initials: A
authors.lastname: Riaza
authors.forename: Janne
authors.initials: J
authors.lastname: Nielsen
authors.forename: Jette
authors.initials: J
authors.lastname: Melchiorsen
authors.forename: Sigmund
authors.initials: S
authors.lastname: Jensen
authors.forename: Hazel
authors.initials: H
authors.lastname: Duncan
authors.forename: Peter
authors.initials: P
authors.lastname: Ahrens
authors.forename: Harry
authors.initials: H
authors.lastname: Birkbeck
authors.forename: Lone
authors.initials: L
authors.lastname: Gram
mesh_terms: D000818:Animals; D000898:Antibiosis / Q000502:physiology*; D016172:DNA Fingerprinting; D004275:DNA, Ribosomal / Q000737:chemistry / Q000302:isolation & purification; D005393:Fish Diseases / Q000517:prevention & control*; D005412:Flatfishes / Q000382:microbiology*; D007814:Larva / Q000254:growth & development; D010802:Phylogeny; D019936:Probiotics; D031161:Pseudoalteromonas / Q000145:classification / Q000302:isolation & purification / Q000502:physiology*; D019105:Random Amplified Polymorphic DNA Technique; D041904:Roseobacter / Q000145:classification / Q000302:isolation & purification / Q000502:physiology*; D017422:Sequence Analysis, DNA; D014733:Vibrio / Q000145:classification / Q000302:isolation & purification / Q000502:physiology*
chemical_list: D004275:DNA, Ribosomal