The Effects of Eubacterium cellulosolvens 5494, a Possible Probiont, on Growth Rates and Hepatic IGF-1 Expression in Oreochromis niloticus

The use of probiotics has been shown to reduce infection and mortality, while increasing growth rates in aquaculture species. Most of these aforementioned studies have utilized facultative anaerobes. In this study, the effects of Eubacterium cellulosolvens 5494, a gram positive, cellulolytic, strict anaerobe isolated from bovine rumen was addressed as a potential probiont. This bacterium has been shown to efficiently degrade cellulose, which is frequently used as filler in commercial fish feed. Commercial feed was supplemented with E. cellulosolvens and presented to Oreochromis niloticus fry on three separate occasions over the course of the first 10 days of the experiment.  O. niloticus fry were maintained in 37.8 L tanks (at a density of 25 fish per tank) for a total of 45 days. Fish that received the E. cellulosolvens supplemented feed were significantly (P < 0.1) larger (3.66g ± 0.29g; n = 75) than the control fish (2.76g ± 0.51g; n = 75). Liver tissue samples were also collected from these fish for comparisons of insulin-like growth factor 1 (IGF-1) expression patterns, using quantitative real-time PCR methodology, in response to probiotic treatments. IGF-1 is an important hormone within the somatotropic axis and is essential for stimulating maximal growth. Real-time PCR was used to analyze expression. Treated O. niloticus had significantly (P <0.1) higher expression (6.31 ± 0.22 pg/ug total RNA) than the control fish (4.85 ± 0.08 pg/ug total RNA). These data may help establish links between growth, molecular mechanisms of growth signals and anaerobic bacteria in the digestive tracts of aquaculture species.