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An artificial biofilm probiotic-supplemented diet was shown to enhance the growth and survival of post-larval South African abalone, Haliotis midae. To ensure the effectiveness of the probiotic bacterium Vibrio midae K811 in an aquaculture environment, we wished to investigate whether V. midae K811 reaches the abalone intestinal tract where it is expected to exert its probiotic effect. Thus, the aim of this study was to investigate the colonization potential of V. midae K811 and to localise the probiotic within the gastrointestinal tract of post-larval H. midae. The Tn9 cat gene incorporated in V. midae K811 was PCR amplified from total DNA isolated from whole abalone homogenates up to 10 days following the cessation of feeding abalone with the probiotic-supplemented diet, while viable V. midae K811 was detected in abalone homogenates up to 25 days after the post-larval abalone had been switched from an alginate surface supplemented with V. midae K811 to a surface supplemented with Cocconeis sp. Furthermore, in situ hybridization using two Tn9 cat gene-specific DIG-labelled oligonucleotide probes detected V. midae K811 in the intestine of post-larval H. midae, confirming that the probiotic reaches the digestive tract of post-larval abalone placed on an alginate biofilm supplemented with the probiotic, and that the bacterium can persist in the abalone digestive tract for a period of at least 3 weeks. |
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