Fernandez, E.M., Kennedy, S.B., Dutka-Gianelli, J. Gensler, A.L., Tucker, J.W., Jr.
Abstract:
Invasion by pathogenic bacteria such as Vibrio sp. is a major problem in marine larval fish culture. In healthy animals a balance of microorganisms in the gut enhances absorption of nutrients and increases resistance to infectious diseases. The balance is easily altered by many factors that promote overgrowth by pathogens and reduce survival of larvae. Probiotic organisms are used to improve the balance of intestinal microflora by reducing the number of pathogens and promoting the growth of beneficial bacteria such as Lactobacillus spp.
The two goals of this study were to modify the microbial flora (e.g., decrease numbers of Vibrio spp.) of wild copepods (Acartia tonsa) reared in 20-L tanks by adding HBOI Bacillus no. 48 and then to use the copepods to deliver the Bacillus to fish larvae.
Bacteria isolated daily for 3 days from treated and control copepods were cultured on TSA-1% NaCl. Gram staining, 3% KOH test, and morphology were used for preliminary classification of the bacteria.
Mean number of gram negative colony types was 1.17 in treated copepods and 2.50 in controls. Mean number of gram positive types was 2.67 in treated copepods and 3.17 in controls.
When control and treated copepods were fed to 7-14 day old tomato clownfish (Amphiprion frenatus) larvae in a preliminary experiment, differences in growth were not detected.
(Harbor Branch Oceanographic Institution, 5600 North U.S. Highway 1, Fort Pierce, FL 34946, USA)
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