Bacteria associated with early life stages of halibut, Hippoglossus hippoglossus L., inhibit growth of a pathogenic Vibrio sp.

Abstract Bacteria capable of inhibiting growth of a pathogenic Vibrio sp. were isolated from the gastrointestinal tract of cultured halibut larvae during the first feeding and weaning stages. No such bacteria were found among isolates from the surface of eggs or the gastrointestinal tract of yolk sac larvae. The fraction of pathogen-inhibitors among the total number of isolates ranged between 0–100% (first feeding) and 0–66% (weaning). All pathogen-inhibitors were Gram-negative rods, and 95% were oxidase and catalase positive fermentative isolates, capable of producing acid aerobically from a varying range of carbohydrates. These isolates possessed the characteristics of the Vibrio/Aeromonas -group, but only 19% were sensitive to the vibriostatic agent 0/129. Isolates from eggs and yolk sac larvae were dominated by bacteria belonging to the Cytophaga/Flexibacter/Flavobacterium - group. The high fraction of isolates with the ability to inhibit growth of the pathogenic Vibrio sp. among the total number of isolates indicates that pathogen inhibition may be an important mutualistic role of the intestinal flora of early life stages of halibut.