Modes of action
There have been several hypotheses for probiotics mode of actions in the host, most of the following actions have been observed during in vitro experiments; however there are needs to emphasize that the efficiency of a selected probiotic in vitro may significantly change when administered to the host in its natural environment, probiotic organisms are influenced by more complex factors among which selective ingestion [9], the manipulation in the intestinal tract [24] and the more complex microbial interactions and/or nutritional environment are of premium importance. We can rely on the aforementioned factors in the success or failure of the probiotic in maintaining its in vivo physiology. In general, there is still an incomplete correlation bond between in vitro and in vivo experiments to explore the claimed mechanisms of probiotic actions. The following are reviews for the different action modes and applications of probiotics in aquatic hosts