CONTROL OF THE BACTERIAL FLORA OF BRACHIONUS PLICATILIS AND ARTEMIA FRANCISCANA BY INCUBATION IN BACTERIAL SUSPENSIONS

P. Makridis, A. J. Fjellheim, J. Skjermo, O. Vadstein-2000

Aquaculture, 185 (3-4): 207-218
Abstract:

The accumulation of bacteria in Brachionus plicatilis and Artemia franciscana during a short-term incubation was quantified using immunocolony blot (ICB) and an enzyme-linked immunosorbent assay (ELISA). Four bacterial strains, isolated from turbot and halibut, were grazed effectively by both species when given at high concentrations (>/= 5×10^7 bacteria/ml). B. plicatilis accumulated 21-63×10^3 bacteria per rotifer and A. franciscana up to 45×10^3 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. plicatilis and A. franciscana were transferred to seawater with added microalgae (Tetraselmis sp., 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 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 for a relatively long period of time (4-24 h).

(Brattora Research Center, Department of Botany, Norwegian University of Science and Technology, Gryta 2, N-7010 Trondheim, Norway)

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