Sponge-associated microbes: A potential probiotics for the management of fish diseases

Abstract

A probiotic is a “live microbial feed supplement which beneficially affects the host animal by improving its intestinal balance”. Probiotics, which are microorganisms or their products with benefit to the host, have found use in aquaculture as a means of disease control, supplementing or even in some cases replacing the use of antimicrobial compounds. A wide range of yeast and Gram-positive and Gram-negative bacteria have been evaluated. However, the mode of action of the probiotics is rarely investigated, but possibilities include competitive exclusion, i.e. the probiotics actively inhibit the colonization of potential pathogens in the digestive tract by antibiosis or by competition for nutrient and/or space, alteration of microbial metabolism and/or by the stimulation of host immunity. Probiotics may stimulate appetite and improve nutrition by the production of vitamins, detoxification of compounds in the diet and by the breakdown of indigestible components. There is accumulating evidence that probiotics are effective at inhibiting a wide range of fish pathogens, but the reasons for the inhibitions are often unstated.