Control of the bacterial flora of Brachionus plicatilis and Artemia franciscana by incubation in bacterial suspensions

The accumulation of bacteria in Brachionus plicatilis and Artemia franciscana during a Ž . short-term incubation was quantified using immunocolony blot ICB and an enzyme-linked Ž . immunosorbent assay ELISA . Four bacterial strains, isolated from turbot and halibut, were Ž 7 y1. grazed effectively by both species when given at high concentrations G5=10 bacteria ml . B. plicatilis accumulated 21–63=10 bacteria per rotifer and A. franciscana up to 45=10 bacteria per metanauplius after 20–60 min of grazing. The composition of the bacterial microflora of the live food organisms changed drastically, as the bioencapsulated strains comprised up to 100% of the total count of colony-forming units. After incubation in the bacterial suspensions, B. Ž plicatilis and A. franciscana were transferred to seawater with added microalgae Tetraselmis sp., y1. 2 mg C l , to evaluate the persistence of the changed bacterial composition in conditions similar to those present in a first feeding tank. The bioencapsulated bacteria decreased in numbers, but in most cases remained present in both live food organisms after 24 h. It is possible, after a Ž . short-term incubation, to replace opportunistic r-selected bacteria present in the live food cultures with other bacteria, which persist as a dominant part of the bacterial flora of the live food Ž . for a relatively long period of time 4–24 h . q 2000 Elsevier Science B.V. All rights reserved.